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Home / DTC / P0118 — Engine Coolant Temperature Sensor 1 Circuit High

P0118 — Engine Coolant Temperature Sensor 1 Circuit High

Detailed page for trouble code P0118.

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23,694specific
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Code

P0118

Generic P — Powertrain

Engine Coolant Temperature Sensor 1 Circuit High

Brand: Generic
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
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Code

P0118

GWM P — Powertrain

- High Engine Coolant Temperature Sensor

Brand: GWM
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
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Code

P0118

HUMMER P — Powertrain

Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
Repair manuals

Manual library for HUMMER

138

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Code

P0118

HYUNDAI P — Powertrain

Engine Coolant Temperature (ECT) Sensor Circuit – High Input

Brand: HYUNDAI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
371

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HYUNDAI

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Code

P0118

ISUZU P — Powertrain

Engine Coolant Temperature Sensor Circuit High

Brand: ISUZU
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
Repair manuals

Manual library for ISUZU

229

Browse 229 ISUZU manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

ISUZU

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Code

P0118

LAND ROVER P — Powertrain

Engine Coolant Temperature Circuit High Input

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
413

Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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Keep it short and practical. Up to 500 characters.
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Code

P0118

MITSUBISHI P — Powertrain

Engine coolant TEMP.sensor high

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

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+100 karma for a short comment :)
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Code

P0118

VOLKSWAGEN P — Powertrain

Engine Coolant Temperature (ECT) Sensor Circuit High Input

Brand: VOLKSWAGEN
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or high-resistance wiring in the ECT sensor circuit
  • Corroded, loose, or damaged sensor connector
  • Failed ECT (thermistor) sensor
  • Poor or lost ground or reference supply to the sensor
  • Faulty PCM/ECM driver or internal circuit fault
  • Recent repairs or connector disturbance that damaged wiring

Symptoms

  • Illuminated MIL / Check Engine Light
  • Hard cold starts, extended warm-up, or rich running after start
  • Poor fuel economy and possible rough idle
  • Cooling fan inoperative or delayed (fans may not run when needed)
  • Possible overheating if fans never engage or thermostat action is affected

What to check

  • Retrieve freeze-frame and live data for coolant temperature with a scan tool
  • Check for additional related codes (e.g., P0117, P0115, P0119)
  • Visual inspection of sensor, connector, and wiring for damage or corrosion
  • Backprobe sensor connector with ignition ON (engine OFF) to measure signal voltage and reference
  • Measure sensor resistance at two known temps (cold and warm) and compare trend
  • Check for proper reference voltage (typically ~5V) and good ground at harness

Signal parameters

  • Typical reference voltage to sensor: ~5 V (varies by manufacturer)
  • Normal ECT signal voltage: varies with temp (cold → higher voltage; hot → lower voltage)
  • High-circuit fault typically: signal voltage near reference (>4.5 V) or open/infinite resistance
  • Typical thermistor resistance: several kilo-ohms at ambient (drops as temperature rises) — consult vehicle spec
  • Expected change: resistance should decrease as coolant temperature increases (negative temperature coefficient)

Diagnostic algorithm

  1. Verify presence of P0118 and note freeze-frame/conditions using a scan tool.
  2. Inspect sensor and harness for corrosion, bent pins, damage, or recent work that could have disturbed wiring.
  3. With ignition ON (engine OFF) backprobe the sensor signal wire: measure voltage between signal and ground. If voltage is at or near reference (≈ battery/5V) suspect open sensor or open to ground.
  4. Check reference supply at connector (should be ~5V with ignition ON). If reference missing, trace back to fuse/ECM supply.
  5. Check sensor ground continuity back to chassis/ECM ground. Repair any poor grounds.
  6. With sensor removed, measure sensor resistance at ambient and after warming (careful when hot). Resistance should decrease as temperature rises; if open or out of expected trend, replace the sensor.
  7. If wiring and sensor check good, perform continuity/resistance check between sensor connector and ECM pins to rule out open circuit or short.
  8. Wiggle test harness while monitoring live data for intermittent changes. Repair any intermittent wiring faults.
  9. If wiring and sensor are good but problem persists, consider substituting a known-good sensor. If still present, test PCM input circuitry or consult vehicle-specific service info for PCM tests.
  10. Clear codes and perform road/temperature test to confirm repair and that the code does not return.

Likely causes

  • Broken/frayed wire between sensor and ECM (open circuit)
  • Connector corrosion/dirty pins causing high resistance or open
  • ECT sensor element failed open or out of range
  • Blown fuse or interrupted 5V reference or sensor ground
  • PCM input circuit failure (less common)

Fault status

⚠️ Status
P0118 — ECT Sensor 1 Circuit High: sensor signal high or open circuit detected (ECM reading abnormally low coolant temp).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

P0117 P0115 P0119 P0125 P0128
626

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