P0187
Fuel Temperature Sensor B Circuit Low
If your vehicle's onboard computer has flagged the diagnostic trouble code P0187, it refers to a detected anomaly regarding "Fuel Temperature Sensor B Circuit Low". This systemic engine fault needs a targeted check before symptoms expand.
Driver's Summary
Your vehicle's computer logged P0187 after detecting a malfunction in the fuel temperature sensor b circuit low system. Typical symptoms include 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
Code P0187 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. The diagnostic runs during closed-loop operation only, ensuring the engine is at full operating temperature and the PCM's fuel trim feedback loop is active before confirming any out-of-range condition. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
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
Module replacement should always be the last resort for P0187 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Sensor replacement: 100 - 350