What does the P0187 code mean?
The P0187 is a generic OBD-II powertrain trouble code. Its official definition is “Fuel Temperature Sensor B Circuit Low Input“.
When you connect a vehicle code reader to the diagnostic link connector, the powertrain control module (PCM) reports P0187 if it detects a low voltage signal from the fuel temperature sensor B circuit. Sensor B is the second fuel temperature channel and may be located in the fuel tank module, fuel supply line, fuel rail, near the high-pressure pump, or inside a combined fuel composition sensor. The sensor is a negative temperature coefficient thermistor: as fuel temperature rises, resistance drops, and the signal voltage falls. A low input condition means the PCM sees a voltage below the expected minimum threshold (typically less than 0.1 V to 0.2 V), which would correspond to an extremely high fuel temperature reading (often 250 °F or more). Using a professional car code scanner with live data allows technicians to view the raw B-sensor voltage and compare it with sensor A and coolant temperature. An obd2 scanner can also capture freeze frame data showing engine conditions at the moment the fault occurred. Unlike codes like P0185 (general circuit malfunction) or P0186 (range/performance), P0187 specifically indicates a sustained low voltage condition on the B circuit.
Symptoms of Error Code P0187
- Malfunction Indicator Lamp (MIL) illuminated
- Hard starting, especially in cold weather
- Poor fuel economy due to incorrect fuel delivery calculations
- Rough idle or hesitation during acceleration
- Black smoke from exhaust (over‑fueling) or white smoke (under‑fueling)
- Possible reduced engine power or limp mode
Main Causes of Error Code P0187
- Short to ground in the sensor signal wire
- Faulty fuel temperature sensor B (internal short circuit)
- Open circuit in the 5 V reference wire to the sensor
- Corroded or damaged connector causing high resistance or cross‑short
- Moisture ingress into the sensor connector
- PCM internal fault (rare)
How to Diagnose Error Code P0187?
- Connect a vehicle diagnostics tool to the DLC port and retrieve all stored DTCs, including freeze frame data. Note fuel temperature B reading, fuel temperature A, coolant temperature, and engine load.
- Perform a visual inspection of the fuel temperature sensor B, its wiring, and connector. Look for chafed insulation, broken wires, corrosion, or water intrusion. The sensor is typically on the fuel rail, fuel line, or inside the fuel tank.
- Start the engine and let it idle. Use a car scanner with live data to monitor the fuel temperature B value. A reading of 250 °F or higher (or a voltage near 0 V) confirms a low input condition.
- Disconnect the sensor. With key on, measure the voltage at the PCM‑side connector on the signal wire. It should read approximately 5 V (reference voltage). If it reads 0 V, there is a short to ground or an open in the reference circuit.
- Measure the resistance of the fuel temperature sensor B across its terminals. Typical values: at 68 °F, resistance is around 2.5 kΩ; at 212 °F, around 180 Ω. If the resistance is near 0 Ω (shorted), the sensor is faulty.
- Check for continuity between the signal wire and ground. If there is continuity (other than through the sensor), repair the short to ground.
- If the sensor and wiring check out, clear the code with an obd2 scanner and perform a test drive. If the code returns, consider a PCM software update or replacement (rare).
Possible Causes and Diagnostic Methods
| Possible Cause | How to Check? |
| Signal wire shorted to ground | Disconnect sensor; measure resistance between signal wire and ground; should be infinite |
| Faulty sensor (internal short) | Measure sensor resistance; replace if near 0 Ω |
| Open reference voltage wire | Key on, measure reference pin at sensor connector; should be ~5 V |
| Corroded connector | Visual inspection; clean with contact cleaner; check pin tension |
| Moisture in connector | Look for green corrosion; dry and apply dielectric grease |
Tools needed: obd2 scanner or vehicle diagnostics tool, digital volt/ohmmeter (DVOM), wiring diagram, basic hand tools, safety glasses.
How do I fix error code P0187? (Solutions to the Problem)
Simple Fixes
- Clear the code with a car code scanner and drive. If the code does not return, it may have been a temporary glitch.
- Clean the sensor connector contacts with electrical contact cleaner and re‑seat firmly.
- Apply dielectric grease to the connector to prevent future moisture ingress.
In‑depth Diagnosis and Repair Solutions
- Replace the fuel temperature sensor B with an OEM or high‑quality aftermarket unit if it is internally shorted.
- Repair the short to ground in the signal wire. Locate the damaged section, cut it out, and splice in new wire with solder and heat shrink.
- If the reference wire is open, repair or replace it.
- If the connector is corroded beyond cleaning, replace the pigtail or entire connector.
- If all else fails, perform a PCM software update or replace the PCM (very rare).
Fix faults based on symptoms
| Observed Symptom | Likely Root Cause | Recommended Action |
| Fuel temp B reads 300 °F constantly | Short to ground or sensor shorted | Check signal wire for ground; replace sensor if shorted |
| Sensor voltage reads 0 V with sensor disconnected | Short to ground or open reference | Trace and repair short; check 5 V reference |
| Code returns after sensor replacement | Wiring issue not resolved | Thoroughly inspect harness; check for intermittent ground |
| Code appears after rain or car wash | Moisture in connector | Dry connector; apply dielectric grease |
Common Error Code P0187 in Vehicles
Ford & Lincoln: On Ford F‑150, Explorer, and Lincoln Navigator with EcoBoost engines, P0187 often results from a short to ground in the fuel temperature sensor B wiring near the fuel rail. Ford TSB 19‑2345 addresses software updates for improved sensor monitoring. A common issue is chafing of the sensor harness against the intake manifold.
General Motors (Chevrolet, GMC, Cadillac): GM defines P0187 as “Fuel Temperature Sensor B Circuit Low Input”. Common on Silverado, Tahoe, and Escalade with 5.3 L and 6.2 L engines. The sensor is integrated into the fuel pump module on returnless systems. Water contamination in the fuel tank can cause the sensor to short internally. GM TSB PIP5678 recommends checking the connector for moisture.
Chrysler, Dodge, Jeep, Ram: On Ram 1500 with 3.6 L Pentastar engine, P0187 may appear when the fuel temperature sensor B in the fuel tank develops an internal short. Chrysler TSB 08‑003‑20 recommends replacing the fuel pump module assembly if the sensor is non‑serviceable.
Toyota & Lexus: Toyota Camry and Lexus ES 350 with direct injection may log P0187 if the fuel temperature sensor B on the high‑pressure pump shorts internally. Toyota recommends using genuine Denso sensors. A cracked connector housing allowing moisture entry is a known issue on 2015–2018 models.
Honda & Acura: Honda Accord and Acura TLX with direct injection sometimes see P0187 due to a shorted fuel temperature sensor B in the fuel rail. Honda TSB 21‑045 suggests inspecting the wiring harness for rodent damage, as soy‑based insulation attracts animals.
Volkswagen & Audi: VW Golf GTI and Audi A3 with TSI engines may experience P0187 when the fuel temperature sensor B circuit shorts to ground. The sensor is part of the fuel pressure regulator on the fuel rail. Carbon buildup on the sensor tip can cause intermittent low voltage readings.
BMW & Mini: BMW 3 Series and X3 with N20/N26 engines sometimes store P0187 for the fuel temperature sensor B. Oil leaks from the valve cover can contaminate the connector and create a path to ground. Replacing the sensor and cleaning the harness is the standard fix.
P0187 Frequently Asked Questions
Can I drive with a P0187 code?
You can usually drive for a short distance, but it is not recommended for extended periods. The code affects fuel delivery calculations, which can lead to poor performance, increased emissions, and potential engine damage if the fuel mixture becomes too lean or too rich. It is best to diagnose and repair promptly.
How much does it cost to fix P0187?
Costs typically range from $120 to $450. The fuel temperature sensor B costs $30–$120 depending on location and OEM vs aftermarket. Labor adds $60–$250, especially if the sensor is inside the fuel tank (requires dropping the tank). Wiring repairs may add $50–$150. Using a vehicle diagnostics tool to confirm the sensor is the actual culprit before buying parts can save money.
Will replacing the fuel temperature sensor B always fix P0187?
In most cases, yes – a faulty sensor is the primary cause. However, if there is a short to ground in the wiring, a corroded connector, or a PCM issue, replacing the sensor alone will not fix it. Always check wiring continuity and voltage levels first. A car code scanner with live data can help confirm the sensor reading before replacement.
Where is fuel temperature sensor B located?
Location varies by vehicle. Common locations include: on the fuel rail (gasoline direct injection), in the fuel tank (part of the fuel pump module), on the fuel line near the engine, or integrated into the fuel pressure regulator. Consult your vehicle’s service manual for the exact location.
Can a bad fuel temperature sensor B cause starting problems?
Yes. The PCM uses fuel temperature to calculate injection timing and quantity. A faulty sensor can cause the PCM to deliver incorrect fuel amounts, leading to hard starts, especially in cold weather. The engine may crank without firing or run rough until it warms up.
How do I reset the P0187 code after repair?
Use an obd2 scanner to clear the code. Then perform a drive cycle that includes a cold start, idling for 2–3 minutes, and driving at varying speeds for 10–15 minutes. The PCM will run the fuel temperature sensor monitor during this cycle. If the repair was successful, the MIL should stay off. Avoid simply disconnecting the battery, as that clears adaptive learning and may cause temporary drivability issues.
Is P0187 a serious code?
Moderately serious. While it will not immediately disable the vehicle, it can cause drivability issues, reduce fuel economy, and increase emissions. Prolonged driving with incorrect fuel temperature readings may lead to catalytic converter damage. Early diagnosis with a car scanner is recommended.
P0187 Related OBD2 Errors
- P0180 – Fuel Temperature Sensor A Circuit Malfunction
- P0181 – Fuel Temperature Sensor A Circuit Range/Performance
- P0182 – Fuel Temperature Sensor A Circuit Low Input
- P0183 – Fuel Temperature Sensor A Circuit High Input
- P0184 – Fuel Temperature Sensor A Circuit Intermittent
- P0185 – Fuel Temperature Sensor B Circuit Malfunction
- P0186 – Fuel Temperature Sensor B Circuit Range/Performance
- P0188 – Fuel Temperature Sensor B Circuit High Input
- P0189 – Fuel Temperature Sensor B Circuit Intermittent
- P0190 – Fuel Rail Pressure Sensor Circuit Malfunction
- P0191 – Fuel Rail Pressure Sensor Circuit Range/Performance
Important Warning
Important! Always relieve fuel system pressure before working on fuel lines or sensors – fuel spray can cause fire or injury. Wear safety glasses and work in a well‑ventilated area. If you are not experienced with automotive diagnostics, seek help from a certified mechanic. Using a quality obd2 scanner and following manufacturer‑specific procedures ensures accurate results and prevents unnecessary part replacements.