Fuel Temperature Sensor B Circuit Low Input
The P0187 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the fuel temperature sensor 'B' that is lower than the expected range. This sensor monitors the temperature of the fuel in the fuel system, typically on diesel engines. A low input suggests a short to ground, a faulty sensor, or wiring issues. This can affect fuel delivery and combustion, potentially leading to performance problems.
01. Most Common Causes
- Faulty fuel temperature sensor B
- Short to ground in sensor circuit
- Open or shorted wiring or connector
- Corroded or damaged connector pins
- ECM internal fault (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially when hot
- Poor fuel economy
- Rough idle or hesitation
- Reduced engine power
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the fuel temperature sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Measure the sensor's resistance and compare to manufacturer specifications; replace if out of range.
Step 4: Check for voltage at the sensor connector with key on; should be around 5V reference. If low, repair short to ground.
Step 5: If wiring and sensor are okay, test the ECM's input circuit; if faulty, replace ECM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause poor performance and potential engine damage. Short trips to a repair shop are okay.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the sensor location and labor rates.