Damaged, chafed or corroded wiring to the fuel temperature sensor B (open circuit, short to ground or short to voltage); Loose, corroded or contaminated connector at the sensor or control unit; Faulty fuel temperature sensor B (internal resistance out of range or stuck); Fuel leak or contamination at the sensor affecting the sensor or its connector, where the sensor is in the fuel rail, pump or filter housing; Sensor reference voltage or ground fault shared with other sensors; Fault inside the engine control unit.

P0185

Fuel Temperature Sensor B Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
85: FaultThe specific fault in that area

What it means

P0185 is the generic code for a fault in the fuel temperature sensor 'B' circuit. The engine control unit monitors the sensor's signal voltage and sets the code when it is outside the expected range or does not make sense, for example a short to ground, short to voltage or open circuit. Which fuel temperature sensor counts as 'B' and where it is fitted depends on the vehicle and engine, so check the manufacturer's information.

Symptoms

Engine warning light on
Hard or extended starting, especially when hot or cold
Rough idle or hesitation under load
Poor fuel economy
Reduced power if the control unit uses a default fuel temperature value
Possible no symptoms other than the warning light

Possible causes

Damaged, chafed or corroded wiring to the fuel temperature sensor B (open circuit, short to ground or short to voltage)likely
Loose, corroded or contaminated connector at the sensor or control unitlikely
Faulty fuel temperature sensor B (internal resistance out of range or stuck)likely
Fuel leak or contamination at the sensor affecting the sensor or its connector, where the sensor is in the fuel rail, pump or filter housingpossible
Sensor reference voltage or ground fault shared with other sensorspossible
Fault inside the engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other sensor circuit codes are present, as a shared reference or ground fault may be involved
Find out from the manufacturer's information which sensor is 'B' and where it is on this engine
Inspect the sensor, connector and harness for damage, chafing, heat damage, fuel contamination, corrosion and bent or pushed-back pins
Check live data for fuel temperature: with the engine cold it should be close to ambient and intake temperature, and a reading stuck at an extreme suggests a short or open circuit
Unplug the sensor and check the live reading moves to the extreme value expected for an open circuit, then bridge the connector terminals if the manufacturer's procedure allows, to confirm the wiring and control unit respond
Measure the sensor resistance and compare it with the manufacturer's temperature specification
Check the reference voltage, signal and ground at the connector, then test the wiring for continuity and shorts back to the control unit
Clear the code and road test to confirm the fault does not return

How to fix

Repair or replace damaged wiring and connector terminals
Clean or replace a corroded or contaminated connector
Replace the fuel temperature sensor B, using a new seal if one is specified, and make sure there are no fuel leaks
Repair the shared reference or ground fault if other sensor circuits are affected
Repair or replace the engine control unit only after wiring and sensor faults have been ruled out, following the manufacturer's procedure

Can I keep driving?

Low severity

The car can usually be driven while you book it in, as the control unit normally falls back on a default value. If starting, running or power is noticeably affected, or you can smell fuel, get it checked promptly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.