Code
P0187
Generic
P — Powertrain
Fuel Temperature Sensor B Circuit Low
Views:
UK: 26
EN: 34
RU: 34
AI status
Completed
Completed
100%
Causes
- Short to ground in the fuel temperature sensor B wiring
- Open or damaged wiring or broken connector pins
- Corroded or loose sensor connector
- Failed fuel temperature sensor (thermistor)
- Poor or missing sensor ground or ECU ground problem
- Faulty engine control module (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Stored P0187 trouble code and possible related data PIDs out of range
- Incorrect fuel temperature reading in scan tool (very low or stuck near 0)
- Poor driveability: rich running, rough idle, decreased fuel economy or increased emissions (depending on control strategy)
- Hard starting in some conditions
What to check
- Read freeze frame and live data: confirm fuel temperature B PID is low or pegged
- Check for other stored codes that may point to wiring or PCM issues
- Visually inspect sensor connector and wiring harness for damage, corrosion, or contamination
- Backprobe sensor signal with key ON (engine OFF) to measure voltage
- Measure sensor resistance (with sensor disconnected) at known temperatures if service data available
- Check continuity between sensor connector ground and chassis ground and between sensor signal and PCM input
Signal parameters
- Expected signal type: thermistor (resistive) sensor feeding an ECU voltage-sensing circuit
- Low-circuit symptom: signal voltage extremely low (near 0 V) or resistance abnormally low indicating short to ground
- Normal behavior: sensor resistance varies with temperature (higher resistance when cold, lower when hot) and voltage signal changes accordingly
- If available, compare live PID voltages/resistance to manufacturer specification and to Fuel Temp Sensor A
Diagnostic algorithm
- Retrieve freeze-frame and live data; confirm P0187 is active and verify fuel temp B reading vs sensor A (if present).
- Visually inspect connector and wiring for damage, corrosion, melted insulation, or signs of fuel contamination. Repair as needed.
- With key ON (engine OFF), backprobe the sensor signal pin and measure voltage. A very low voltage (~0 V) indicates a short to ground or internal shorted sensor. Do not crank while diagnosing unless required.
- Disconnect sensor and measure resistance across sensor terminals. Compare to service specification or to known-good sensor behavior (resistance should change with temperature).
- If sensor resistance is normal, check continuity from the sensor signal pin at the connector to the ECM input pin; look for shorts to ground or other circuits.
- Wiggle-test the harness while monitoring the signal to find intermittent faults.
- Repair wiring, connector, or sensor as identified. Replace sensor if it fails resistance/voltage checks.
- After repair, clear codes and road-test to confirm code does not return and fuel temp PID behaves normally.
- If wiring and sensor check good, test or replace ECM if manufacturer procedures indicate ECM input failure.
Likely causes
- Corroded/contaminated connector or pin making low-voltage contact
- Wiring routed against chassis or rubbed through causing short-to-ground
- Failed/shorted fuel temperature sensor B
- Intermittent connector seating or bent terminal
- PCM/ECM input circuit fault (least likely)
Fault status
Status
Fuel Temperature Sensor B Circuit Low - sensor signal below expected threshold (possible short to ground or low-voltage condition).
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
P0187
GWM
P — Powertrain
- Low Temperature Sensor B
Views:
UK: 16
EN: 18
RU: 24
AI status
Completed
Completed
100%
Causes
- Short to ground in the fuel temperature sensor B wiring
- Open or damaged wiring or broken connector pins
- Corroded or loose sensor connector
- Failed fuel temperature sensor (thermistor)
- Poor or missing sensor ground or ECU ground problem
- Faulty engine control module (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Stored P0187 trouble code and possible related data PIDs out of range
- Incorrect fuel temperature reading in scan tool (very low or stuck near 0)
- Poor driveability: rich running, rough idle, decreased fuel economy or increased emissions (depending on control strategy)
- Hard starting in some conditions
What to check
- Read freeze frame and live data: confirm fuel temperature B PID is low or pegged
- Check for other stored codes that may point to wiring or PCM issues
- Visually inspect sensor connector and wiring harness for damage, corrosion, or contamination
- Backprobe sensor signal with key ON (engine OFF) to measure voltage
- Measure sensor resistance (with sensor disconnected) at known temperatures if service data available
- Check continuity between sensor connector ground and chassis ground and between sensor signal and PCM input
Signal parameters
- Expected signal type: thermistor (resistive) sensor feeding an ECU voltage-sensing circuit
- Low-circuit symptom: signal voltage extremely low (near 0 V) or resistance abnormally low indicating short to ground
- Normal behavior: sensor resistance varies with temperature (higher resistance when cold, lower when hot) and voltage signal changes accordingly
- If available, compare live PID voltages/resistance to manufacturer specification and to Fuel Temp Sensor A
Diagnostic algorithm
- Retrieve freeze-frame and live data; confirm P0187 is active and verify fuel temp B reading vs sensor A (if present).
- Visually inspect connector and wiring for damage, corrosion, melted insulation, or signs of fuel contamination. Repair as needed.
- With key ON (engine OFF), backprobe the sensor signal pin and measure voltage. A very low voltage (~0 V) indicates a short to ground or internal shorted sensor. Do not crank while diagnosing unless required.
- Disconnect sensor and measure resistance across sensor terminals. Compare to service specification or to known-good sensor behavior (resistance should change with temperature).
- If sensor resistance is normal, check continuity from the sensor signal pin at the connector to the ECM input pin; look for shorts to ground or other circuits.
- Wiggle-test the harness while monitoring the signal to find intermittent faults.
- Repair wiring, connector, or sensor as identified. Replace sensor if it fails resistance/voltage checks.
- After repair, clear codes and road-test to confirm code does not return and fuel temp PID behaves normally.
- If wiring and sensor check good, test or replace ECM if manufacturer procedures indicate ECM input failure.
Likely causes
- Corroded/contaminated connector or pin making low-voltage contact
- Wiring routed against chassis or rubbed through causing short-to-ground
- Failed/shorted fuel temperature sensor B
- Intermittent connector seating or bent terminal
- PCM/ECM input circuit fault (least likely)
Fault status
Status
Fuel Temperature Sensor B Circuit Low - sensor signal below expected threshold (possible short to ground or low-voltage condition).
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
Your experience will help others
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Was this AI description helpful?
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👍 Like
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Send to email
Code
P0187
HUMMER
P — Powertrain
Fuel Temperature Sensor 2 Circuit Low Voltage
Views:
UK: 17
EN: 24
RU: 22
AI status
Completed
Completed
100%
Causes
- Short to ground in the fuel temperature sensor B wiring
- Open or damaged wiring or broken connector pins
- Corroded or loose sensor connector
- Failed fuel temperature sensor (thermistor)
- Poor or missing sensor ground or ECU ground problem
- Faulty engine control module (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Stored P0187 trouble code and possible related data PIDs out of range
- Incorrect fuel temperature reading in scan tool (very low or stuck near 0)
- Poor driveability: rich running, rough idle, decreased fuel economy or increased emissions (depending on control strategy)
- Hard starting in some conditions
What to check
- Read freeze frame and live data: confirm fuel temperature B PID is low or pegged
- Check for other stored codes that may point to wiring or PCM issues
- Visually inspect sensor connector and wiring harness for damage, corrosion, or contamination
- Backprobe sensor signal with key ON (engine OFF) to measure voltage
- Measure sensor resistance (with sensor disconnected) at known temperatures if service data available
- Check continuity between sensor connector ground and chassis ground and between sensor signal and PCM input
Signal parameters
- Expected signal type: thermistor (resistive) sensor feeding an ECU voltage-sensing circuit
- Low-circuit symptom: signal voltage extremely low (near 0 V) or resistance abnormally low indicating short to ground
- Normal behavior: sensor resistance varies with temperature (higher resistance when cold, lower when hot) and voltage signal changes accordingly
- If available, compare live PID voltages/resistance to manufacturer specification and to Fuel Temp Sensor A
Diagnostic algorithm
- Retrieve freeze-frame and live data; confirm P0187 is active and verify fuel temp B reading vs sensor A (if present).
- Visually inspect connector and wiring for damage, corrosion, melted insulation, or signs of fuel contamination. Repair as needed.
- With key ON (engine OFF), backprobe the sensor signal pin and measure voltage. A very low voltage (~0 V) indicates a short to ground or internal shorted sensor. Do not crank while diagnosing unless required.
- Disconnect sensor and measure resistance across sensor terminals. Compare to service specification or to known-good sensor behavior (resistance should change with temperature).
- If sensor resistance is normal, check continuity from the sensor signal pin at the connector to the ECM input pin; look for shorts to ground or other circuits.
- Wiggle-test the harness while monitoring the signal to find intermittent faults.
- Repair wiring, connector, or sensor as identified. Replace sensor if it fails resistance/voltage checks.
- After repair, clear codes and road-test to confirm code does not return and fuel temp PID behaves normally.
- If wiring and sensor check good, test or replace ECM if manufacturer procedures indicate ECM input failure.
Likely causes
- Corroded/contaminated connector or pin making low-voltage contact
- Wiring routed against chassis or rubbed through causing short-to-ground
- Failed/shorted fuel temperature sensor B
- Intermittent connector seating or bent terminal
- PCM/ECM input circuit fault (least likely)
Fault status
Status
Fuel Temperature Sensor B Circuit Low - sensor signal below expected threshold (possible short to ground or low-voltage condition).
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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HTML ManualYour experience will help others
+100 karma for a short comment :)
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