What does the P0185 code mean?
The P0185 is a generic OBD-II powertrain trouble code. Its official definition is “Fuel Temperature Sensor B Circuit Malfunction“.
When you connect an obd2 scanner to the diagnostic link connector, the powertrain control module (PCM) reports P0185 if it detects an electrical fault in the fuel temperature sensor B circuit. Sensor B is the second fuel temperature channel; vehicles may use it to monitor fuel in a different location, such as the fuel tank module, supply line, fuel rail, near the high-pressure pump, or inside a combined fuel composition sensor assembly. The sensor is typically a thermistor that changes resistance with fuel temperature. The PCM supplies a 5 V reference and ground, then calculates fuel temperature from the signal voltage. If the signal is missing, out of range, unstable, or does not match circuit expectations for a calibrated period, the PCM sets P0185. Using a professional car code scanner with live data allows technicians to view the B-sensor temperature, compare it with sensor A and coolant temperature, and capture freeze frame data such as load, RPM, and fuel trim. A vehicle diagnostics tool that graphs sensor voltage helps separate a bad sensor from wiring faults. Unlike performance codes that point to an inaccurate but plausible reading, P0185 indicates the B circuit itself has an electrical problem.
Symptoms of Error Code P0185
- Malfunction Indicator Lamp (MIL) illuminated
- Hard starting, especially in very cold or very hot conditions
- Reduced fuel economy, sometimes 2–5 MPG lower than normal
- Rough idle or fluctuating idle speed
- Hesitation or stumble during acceleration
- Inaccurate fuel temperature reading on the scan tool
- Possible related flex-fuel, fuel-pressure, or fuel-trim codes
Main Causes of Error Code P0185
- Faulty fuel temperature sensor B (internal open, short, or out of specification)
- Open circuit in the sensor signal, reference, or ground wire
- Short to ground or short to battery voltage in the B-sensor harness
- Corroded, loose, or water-contaminated sensor connector
- Poor ground connection causing high resistance in the circuit
- Damaged wiring from heat, chafing, or rodent damage
- PCM input fault or software calibration error (rare, only after circuit proof)
How to Diagnose Error Code P0185?
- Connect a car scanner to the DLC port and retrieve all DTCs plus freeze frame. Record fuel temperature B, fuel temperature A, coolant temperature, IAT, load, and RPM.
- Check technical service bulletins for the exact model before electrical tests; some B-sensor faults have known harness or PCM updates.
- Visually inspect the fuel temperature sensor B, its connector, and harness. Look for broken wires, melted insulation, corrosion, loose terminals, and moisture near the tank, rail, or pump area.
- Key on, engine off. Use a vehicle code reader live data or meter to confirm B-sensor voltage. With the sensor connected, a healthy 5 V-referenced thermistor circuit usually rests at a plausible partial voltage; a fixed 0 V, 5 V, or battery voltage indicates a circuit fault.
- Disconnect the sensor. Measure reference voltage at the PCM-side connector; it should be around 5 V. Measure ground continuity to chassis. Check the signal wire for short to ground, short to power, and open back to the PCM.
- Measure sensor B resistance at known temperatures. Compare with the manufacturer chart; many fuel temp thermistors read several thousand ohms when cold and a few hundred ohms when hot. Infinite resistance means open; near 0 ohms means shorted.
- If reference, ground, and wiring are good but resistance or live temperature is implausible, replace the B sensor or its assembly.
- Clear the code with an obd2 scanner after repairs and perform a drive cycle with cold start, idle, steady cruise, and acceleration to confirm the B-sensor monitor passes.
Possible Causes and Diagnostic Methods
| Possible Cause | How to Check? |
| Faulty fuel temperature sensor B | Measure resistance at several temperatures; compare to OEM chart; graph voltage with a car scanner |
| Open signal/reference/ground wire | Check continuity from sensor connector to PCM; repair broken circuits |
| Short to ground | With sensor disconnected, test signal wire to ground; should be no continuity |
| Short to battery voltage | Key on, measure signal wire voltage; 12.6 V indicates short to power |
| Corroded connector | Visual inspection; clean terminals; verify voltage drop under load |
| PCM input fault | Only after sensor and all wiring test good; check TSBs and reflash/replace |
Tools needed: obd2 scanner or vehicle diagnostics tool, digital volt/ohmmeter (DVOM), infrared thermometer, manufacturer wiring diagram, fuel pressure gauge if combined with fuel delivery codes, basic hand tools, safety glasses.
How do I fix error code P0185? (Solutions to the Problem)
Simple Fixes
- Clear the code with a car code scanner and drive. If the light returns immediately, do not keep clearing; perform circuit tests first.
- Unplug the B-sensor connector, clean terminals with electrical contact cleaner, apply dielectric grease, and re-seat it firmly.
- Inspect the fuel tank cap and fuel quality; water contamination can mimic a sensor fault.
In-depth Diagnosis and Repair Solutions
- Replace fuel temperature sensor B with an OEM or high-quality aftermarket unit if resistance is out of spec or the sensor fails the temperature sweep test.
- Repair open, shorted, or chafed wiring. Solder and heat-shrink all connections; avoid crimp connectors in exposed areas.
- Replace the connector pigtail if corrosion is deep or pins are damaged.
- For tank-mounted sensors, replace the entire fuel pump module or sender assembly if the sensor is non-serviceable.
- Perform a PCM software update if a relevant TSB exists, and only replace the PCM after all circuit checks pass.
Fix faults based on symptoms
| Observed Symptom | Likely Root Cause | Recommended Action |
| Fuel temp B reads -40 °F constantly | Open circuit or failed sensor | Check continuity and sensor resistance; replace sensor if open |
| Fuel temp B reads 300+ °F when fuel is cold | Short to ground or sensor shorted internally | Test signal wire to ground; replace sensor if shorted |
| Sensor voltage reads 5 V with sensor disconnected | Open signal wire or PCM input issue | Check continuity back to PCM; test with known-good sensor |
| Code returns after sensor replacement | Wiring or connector fault not resolved | Recheck harness thoroughly; consider PCM reflash |
Common Error Code P0185 in Vehicles
Ford & Lincoln: On Ford F-150, Explorer, and Lincoln Navigator with EcoBoost engines, P0185 often results from an open circuit 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 P0185 as “Fuel Temperature Sensor B Circuit Malfunction”. 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 fail open. GM TSB PIP5678 recommends checking the connector for moisture.
Chrysler, Dodge, Jeep, Ram: On Ram 1500 with 3.6 L Pentastar engine, P0185 may appear when the fuel temperature sensor B in the fuel tank develops an open circuit. 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 P0185 if the fuel temperature sensor B on the high-pressure pump fails open. Toyota recommends using genuine Denso sensors. A cracked connector housing is a known issue on 2015–2018 models.
Honda & Acura: Honda Accord and Acura TLX with direct injection sometimes see P0185 due to an open 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 P0185 when the fuel temperature sensor B circuit opens. The sensor is part of the fuel pressure regulator on the fuel rail. Carbon buildup on the sensor tip can cause intermittent high voltage readings.
BMW & Mini: BMW 3 Series and X3 with N20/N26 engines sometimes store P0185 for the fuel temperature sensor B. Oil leaks from the valve cover can contaminate the connector. Replacing the sensor and cleaning the harness is the standard fix.
P0185 Frequently Asked Questions
Can I drive with a P0185 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 P0185?
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 P0185?
In most cases, yes – a faulty sensor is the primary cause. However, if there is an open or short 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 P0185 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 P0185 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.
P0185 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
- P0186 – Fuel Temperature Sensor B Circuit Range/Performance
- P0187 – Fuel Temperature Sensor B Circuit Low Input
- 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.