P0187
Fuel Temperature Sensor B Circuit Low
If your code reader dashboard displays the generic DTC error code P0187, your vehicle is currently experiencing an active failure related to "Fuel Temperature Sensor B Circuit Low". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
P0187 is triggered when the PCM detects an abnormal condition associated with fuel temperature sensor b circuit low. In practice, this fault causes check engine light, overly rich fuel mixture. No immediate danger, but addressing this soon will prevent potential emissions test failures and minor system degradation.
Symptoms
Check engine light, overly rich fuel mixture
Common Causes
- Short to ground in sensor B circuit
- Failed fuel temp sensor B
- Pinched wiring near the secondary fuel tank
- Internal PCM issue
How to Fix
- 1 Trace and repair short to ground
- 2 Replace fuel temperature sensor B
- 3 Reroute wiring away from pinch points
- 4 Test PCM
Technical Explanation
The ECM detects code P0187 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The module measures the voltage return on the 5V reference circuit, comparing it to the expected signal envelope at current engine load and RPM. A deviation greater than the calibrated threshold — typically ±10% outside the normal operating window — flags the fault. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
Immediate safety risk is low with P0187 active. The primary concern is regulatory — this fault will cause a failed emissions test — and the secondary risk is that the small root cause (short to ground in sensor b circuit) becomes a larger problem if ignored for months.
Mechanic's Pro Tip
Before replacing any component on P0187, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Related Fault Codes
Frequently Asked Questions
What does OBD2 code P0187 mean?
OBD2 code P0187 refers to Fuel Temperature Sensor B Circuit Low. If your code reader dashboard displays the generic DTC error code P0187, your vehicle is currently experiencing an active failure related to "Fuel Temperature Sensor B Circuit Low". Proper system troubleshooting is required to safely clear this warning.
What are the most common symptoms of DTC P0187?
Drivers experiencing code P0187 typically report: Check engine light, overly rich fuel mixture.
Is it safe to drive with trouble code P0187 active?
Immediate safety risk is low with P0187 active. The primary concern is regulatory — this fault will cause a failed emissions test — and the secondary risk is that the small root cause (short to ground in sensor b circuit) becomes a larger problem if ignored for months.
How much does it cost to fix code P0187?
The estimated repair cost for P0187 ranges from $100 to $350 USD. Sensor replacement: $100 - $350
Sensor replacement: $100 - $350
Need Professional Diagnostic Assistance?
Always verify sensor signals and wiring integrity with an OBD2 scanner before purchasing replacement parts.
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