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 rail or tank, and a low input typically means the sensor's resistance is too low, often due to a short circuit, faulty sensor, or wiring issues. The ECM uses this data for fuel delivery and timing adjustments, so an incorrect reading can affect engine performance and emissions.
1. Most Common Causes
- Faulty fuel temperature sensor B
- Short circuit in sensor wiring or connector
- Corroded or damaged sensor connector
- Open circuit in sensor ground or signal wire
- ECM failure (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation during acceleration
- Hard starting or stalling
- Black smoke from exhaust (rich mixture)
3. Step-by-Step Diagnosis
Step 1: Connect an OBD2 scanner and verify the code P0187. Check for additional codes related to fuel temperature or fuel system.
Step 2: Visually inspect the fuel temperature sensor B and its wiring for damage, corrosion, or loose connections. Repair or replace as needed.
Step 3: Use a multimeter to measure the sensor's resistance. Compare with manufacturer specifications (typically 2-5 kΩ at 20°C). Replace if out of range.
Step 4: Check the voltage at the sensor connector with the ignition on. Should be around 5V reference. If low, check for shorts to ground or open circuits.
Step 5: If all checks pass, suspect an ECM issue. Perform a ECM reflash or replacement as a last resort.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive long distances with P0187, as it can cause poor engine performance, increased emissions, and potential damage to the catalytic converter due to incorrect fuel mixture.
How much does it cost to fix?▼
The cost to fix P0187 typically ranges from $50 to $150, including parts and labor. The sensor itself costs around $20-$50, and labor is about $30-$100 depending on the vehicle and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.