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Home / DTC / P0199 — Engine Oil Temperature Sensor A Circuit Intermittent/Erratic

P0199 — Engine Oil Temperature Sensor A Circuit Intermittent/Erratic

Detailed page for trouble code P0199.

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22,491specific
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Code

P0199

Generic P — Powertrain

Engine Oil Temperature Sensor A Circuit Intermittent/Erratic

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

Causes

  • Loose, corroded or contaminated connector at the oil temperature sensor
  • Damaged, frayed or broken wiring/harness (intermittent contact)
  • Failed oil temperature sensor (internal intermittent fault)
  • Poor ground or reference voltage to the sensor
  • Oil intrusion/contamination of connector or sensor
  • Intermittent fault in the PCM or its connector

Symptoms

  • Check Engine Light (MIL) illuminated, intermittent or steady
  • Erratic or fluctuating oil temperature readout on dash or scan tool
  • Oil temperature not changing logically during warm-up/cool-down
  • Possible incorrect fan or engine control responses tied to oil temp
  • Possible limp-home or reduced performance on some vehicles (rare)

What to check

  • Read stored freeze-frame and pending codes; note conditions when P0199 set
  • Scan-tool: monitor oil temperature PID for stability while cold, warm, idle and driving
  • Visually inspect sensor connector and harness for oil, corrosion, damage or loose pins
  • Wiggle test wiring and connector while watching live data for interruptions
  • Confirm proper oil level and condition (very contaminated oil can affect connectors)
  • Check for Technical Service Bulletins (TSBs) related to oil temp sensor problems

Signal parameters

  • Sensor type: typically a thermistor (resistance varies with temperature) — most are NTC (resistance decreases as temperature rises)
  • Signal to ECU: analog voltage proportional to resistance (common range ~0.1–5.0 V depending on temperature and circuit design)
  • Expected behavior: smooth, monotonic change in voltage/resistance with temperature (no rapid spikes/dropouts)
  • Operating range: sensor reports from cold (-30 to -40 °C) up to high oil temperatures (100–150 °C), exact spec varies by manufacturer
  • Update character: steady analog change (not a digital/pulsed sensor)

Diagnostic algorithm

  1. Verify the code: read freeze-frame and note engine condition when fault occurred (temp, load, time since start).
  2. Monitor live oil temp PID with a scan tool through cold start, warm-up and steady conditions; look for sudden jumps or dropouts.
  3. Perform a wiggle test on the sensor connector and wiring while observing the live data for intermittent changes.
  4. Visually inspect and disconnect the sensor; check connector pins for corrosion, oil intrusion, bent pins or looseness. Clean and dry if contaminated.
  5. Backprobe the sensor connector with a DVOM/scope. With engine at known temperatures, verify reference voltage (if used), signal voltage stability and good ground.
  6. Measure sensor resistance out of circuit across terminals and compare behavior while gently heating/cooling the sensor (do not immerse in hot oil). Resistance should change smoothly with temperature. If sensor has published spec, compare values.
  7. If intermittent signal persists, use an oscilloscope to observe waveform for spikes/dropouts while wiggling harness; scope is more reliable for intermittent noise.
  8. Repair any found wiring faults: repair broken wires, replace corroded connectors, apply proper sealing and dielectric grease to prevent future contamination.
  9. If wiring and connectors are good but sensor readings remain unstable, replace the oil temperature sensor with correct OEM or equivalent part.
  10. If new sensor and wiring still show intermittent signals, inspect PCM connector and grounds. Replace PCM only after exhaustive wiring and sensor verification.
  11. Clear codes, perform a road/drive cycle and re-scan to confirm the fault does not return.

Likely causes

  • Connector pins corroded or contaminated with oil
  • Wiring harness damaged where it flexes (chafed/broken strand)
  • Failed/aging EOT sensor
  • Poor ground or loose connector at sensor or PCM
  • Oil-soaked connector causing intermittent contact

Fault status

⚠️ Status
Intermittent/erratic signal detected on Engine Oil Temperature Sensor A circuit. PCM recorded voltage/resistance fluctuations outside expected pattern.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

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Code

P0199

GWM P — Powertrain

- Oil temperature sensor fault

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

Causes

  • Loose, corroded or contaminated connector at the oil temperature sensor
  • Damaged, frayed or broken wiring/harness (intermittent contact)
  • Failed oil temperature sensor (internal intermittent fault)
  • Poor ground or reference voltage to the sensor
  • Oil intrusion/contamination of connector or sensor
  • Intermittent fault in the PCM or its connector

Symptoms

  • Check Engine Light (MIL) illuminated, intermittent or steady
  • Erratic or fluctuating oil temperature readout on dash or scan tool
  • Oil temperature not changing logically during warm-up/cool-down
  • Possible incorrect fan or engine control responses tied to oil temp
  • Possible limp-home or reduced performance on some vehicles (rare)

What to check

  • Read stored freeze-frame and pending codes; note conditions when P0199 set
  • Scan-tool: monitor oil temperature PID for stability while cold, warm, idle and driving
  • Visually inspect sensor connector and harness for oil, corrosion, damage or loose pins
  • Wiggle test wiring and connector while watching live data for interruptions
  • Confirm proper oil level and condition (very contaminated oil can affect connectors)
  • Check for Technical Service Bulletins (TSBs) related to oil temp sensor problems

Signal parameters

  • Sensor type: typically a thermistor (resistance varies with temperature) — most are NTC (resistance decreases as temperature rises)
  • Signal to ECU: analog voltage proportional to resistance (common range ~0.1–5.0 V depending on temperature and circuit design)
  • Expected behavior: smooth, monotonic change in voltage/resistance with temperature (no rapid spikes/dropouts)
  • Operating range: sensor reports from cold (-30 to -40 °C) up to high oil temperatures (100–150 °C), exact spec varies by manufacturer
  • Update character: steady analog change (not a digital/pulsed sensor)

Diagnostic algorithm

  1. Verify the code: read freeze-frame and note engine condition when fault occurred (temp, load, time since start).
  2. Monitor live oil temp PID with a scan tool through cold start, warm-up and steady conditions; look for sudden jumps or dropouts.
  3. Perform a wiggle test on the sensor connector and wiring while observing the live data for intermittent changes.
  4. Visually inspect and disconnect the sensor; check connector pins for corrosion, oil intrusion, bent pins or looseness. Clean and dry if contaminated.
  5. Backprobe the sensor connector with a DVOM/scope. With engine at known temperatures, verify reference voltage (if used), signal voltage stability and good ground.
  6. Measure sensor resistance out of circuit across terminals and compare behavior while gently heating/cooling the sensor (do not immerse in hot oil). Resistance should change smoothly with temperature. If sensor has published spec, compare values.
  7. If intermittent signal persists, use an oscilloscope to observe waveform for spikes/dropouts while wiggling harness; scope is more reliable for intermittent noise.
  8. Repair any found wiring faults: repair broken wires, replace corroded connectors, apply proper sealing and dielectric grease to prevent future contamination.
  9. If wiring and connectors are good but sensor readings remain unstable, replace the oil temperature sensor with correct OEM or equivalent part.
  10. If new sensor and wiring still show intermittent signals, inspect PCM connector and grounds. Replace PCM only after exhaustive wiring and sensor verification.
  11. Clear codes, perform a road/drive cycle and re-scan to confirm the fault does not return.

Likely causes

  • Connector pins corroded or contaminated with oil
  • Wiring harness damaged where it flexes (chafed/broken strand)
  • Failed/aging EOT sensor
  • Poor ground or loose connector at sensor or PCM
  • Oil-soaked connector causing intermittent contact

Fault status

⚠️ Status
Intermittent/erratic signal detected on Engine Oil Temperature Sensor A circuit. PCM recorded voltage/resistance fluctuations outside expected pattern.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

P0198 P0197 P0117 P0118 P0128
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Code

P0199

HUMMER P — Powertrain

Engine Oil Temperature Sensor Intermittent

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

Causes

  • Loose, corroded or contaminated connector at the oil temperature sensor
  • Damaged, frayed or broken wiring/harness (intermittent contact)
  • Failed oil temperature sensor (internal intermittent fault)
  • Poor ground or reference voltage to the sensor
  • Oil intrusion/contamination of connector or sensor
  • Intermittent fault in the PCM or its connector

Symptoms

  • Check Engine Light (MIL) illuminated, intermittent or steady
  • Erratic or fluctuating oil temperature readout on dash or scan tool
  • Oil temperature not changing logically during warm-up/cool-down
  • Possible incorrect fan or engine control responses tied to oil temp
  • Possible limp-home or reduced performance on some vehicles (rare)

What to check

  • Read stored freeze-frame and pending codes; note conditions when P0199 set
  • Scan-tool: monitor oil temperature PID for stability while cold, warm, idle and driving
  • Visually inspect sensor connector and harness for oil, corrosion, damage or loose pins
  • Wiggle test wiring and connector while watching live data for interruptions
  • Confirm proper oil level and condition (very contaminated oil can affect connectors)
  • Check for Technical Service Bulletins (TSBs) related to oil temp sensor problems

Signal parameters

  • Sensor type: typically a thermistor (resistance varies with temperature) — most are NTC (resistance decreases as temperature rises)
  • Signal to ECU: analog voltage proportional to resistance (common range ~0.1–5.0 V depending on temperature and circuit design)
  • Expected behavior: smooth, monotonic change in voltage/resistance with temperature (no rapid spikes/dropouts)
  • Operating range: sensor reports from cold (-30 to -40 °C) up to high oil temperatures (100–150 °C), exact spec varies by manufacturer
  • Update character: steady analog change (not a digital/pulsed sensor)

Diagnostic algorithm

  1. Verify the code: read freeze-frame and note engine condition when fault occurred (temp, load, time since start).
  2. Monitor live oil temp PID with a scan tool through cold start, warm-up and steady conditions; look for sudden jumps or dropouts.
  3. Perform a wiggle test on the sensor connector and wiring while observing the live data for intermittent changes.
  4. Visually inspect and disconnect the sensor; check connector pins for corrosion, oil intrusion, bent pins or looseness. Clean and dry if contaminated.
  5. Backprobe the sensor connector with a DVOM/scope. With engine at known temperatures, verify reference voltage (if used), signal voltage stability and good ground.
  6. Measure sensor resistance out of circuit across terminals and compare behavior while gently heating/cooling the sensor (do not immerse in hot oil). Resistance should change smoothly with temperature. If sensor has published spec, compare values.
  7. If intermittent signal persists, use an oscilloscope to observe waveform for spikes/dropouts while wiggling harness; scope is more reliable for intermittent noise.
  8. Repair any found wiring faults: repair broken wires, replace corroded connectors, apply proper sealing and dielectric grease to prevent future contamination.
  9. If wiring and connectors are good but sensor readings remain unstable, replace the oil temperature sensor with correct OEM or equivalent part.
  10. If new sensor and wiring still show intermittent signals, inspect PCM connector and grounds. Replace PCM only after exhaustive wiring and sensor verification.
  11. Clear codes, perform a road/drive cycle and re-scan to confirm the fault does not return.

Likely causes

  • Connector pins corroded or contaminated with oil
  • Wiring harness damaged where it flexes (chafed/broken strand)
  • Failed/aging EOT sensor
  • Poor ground or loose connector at sensor or PCM
  • Oil-soaked connector causing intermittent contact

Fault status

⚠️ Status
Intermittent/erratic signal detected on Engine Oil Temperature Sensor A circuit. PCM recorded voltage/resistance fluctuations outside expected pattern.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

P0198 P0197 P0117 P0118 P0128
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HUMMER

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Code

P0199

LAND ROVER P — Powertrain

intermittent circuit of the engine oil temperature sensor

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

Causes

  • Loose, corroded or contaminated connector at the oil temperature sensor
  • Damaged, frayed or broken wiring/harness (intermittent contact)
  • Failed oil temperature sensor (internal intermittent fault)
  • Poor ground or reference voltage to the sensor
  • Oil intrusion/contamination of connector or sensor
  • Intermittent fault in the PCM or its connector

Symptoms

  • Check Engine Light (MIL) illuminated, intermittent or steady
  • Erratic or fluctuating oil temperature readout on dash or scan tool
  • Oil temperature not changing logically during warm-up/cool-down
  • Possible incorrect fan or engine control responses tied to oil temp
  • Possible limp-home or reduced performance on some vehicles (rare)

What to check

  • Read stored freeze-frame and pending codes; note conditions when P0199 set
  • Scan-tool: monitor oil temperature PID for stability while cold, warm, idle and driving
  • Visually inspect sensor connector and harness for oil, corrosion, damage or loose pins
  • Wiggle test wiring and connector while watching live data for interruptions
  • Confirm proper oil level and condition (very contaminated oil can affect connectors)
  • Check for Technical Service Bulletins (TSBs) related to oil temp sensor problems

Signal parameters

  • Sensor type: typically a thermistor (resistance varies with temperature) — most are NTC (resistance decreases as temperature rises)
  • Signal to ECU: analog voltage proportional to resistance (common range ~0.1–5.0 V depending on temperature and circuit design)
  • Expected behavior: smooth, monotonic change in voltage/resistance with temperature (no rapid spikes/dropouts)
  • Operating range: sensor reports from cold (-30 to -40 °C) up to high oil temperatures (100–150 °C), exact spec varies by manufacturer
  • Update character: steady analog change (not a digital/pulsed sensor)

Diagnostic algorithm

  1. Verify the code: read freeze-frame and note engine condition when fault occurred (temp, load, time since start).
  2. Monitor live oil temp PID with a scan tool through cold start, warm-up and steady conditions; look for sudden jumps or dropouts.
  3. Perform a wiggle test on the sensor connector and wiring while observing the live data for intermittent changes.
  4. Visually inspect and disconnect the sensor; check connector pins for corrosion, oil intrusion, bent pins or looseness. Clean and dry if contaminated.
  5. Backprobe the sensor connector with a DVOM/scope. With engine at known temperatures, verify reference voltage (if used), signal voltage stability and good ground.
  6. Measure sensor resistance out of circuit across terminals and compare behavior while gently heating/cooling the sensor (do not immerse in hot oil). Resistance should change smoothly with temperature. If sensor has published spec, compare values.
  7. If intermittent signal persists, use an oscilloscope to observe waveform for spikes/dropouts while wiggling harness; scope is more reliable for intermittent noise.
  8. Repair any found wiring faults: repair broken wires, replace corroded connectors, apply proper sealing and dielectric grease to prevent future contamination.
  9. If wiring and connectors are good but sensor readings remain unstable, replace the oil temperature sensor with correct OEM or equivalent part.
  10. If new sensor and wiring still show intermittent signals, inspect PCM connector and grounds. Replace PCM only after exhaustive wiring and sensor verification.
  11. Clear codes, perform a road/drive cycle and re-scan to confirm the fault does not return.

Likely causes

  • Connector pins corroded or contaminated with oil
  • Wiring harness damaged where it flexes (chafed/broken strand)
  • Failed/aging EOT sensor
  • Poor ground or loose connector at sensor or PCM
  • Oil-soaked connector causing intermittent contact

Fault status

⚠️ Status
Intermittent/erratic signal detected on Engine Oil Temperature Sensor A circuit. PCM recorded voltage/resistance fluctuations outside expected pattern.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

Similar codes

P0198 P0197 P0117 P0118 P0128
320

Browse 320 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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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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