P0185: Fuel Temperature Sensor B Circuit

What it means

The ECU detects an electrical fault in the fuel temperature sensor B circuit (second sensor used on systems with separate supply/return temperature monitoring or twin-tank arrangements).

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Fuel Temperature sensor B measures fuel temperature at a second monitoring point used by some fuel systems, such as separate supply and return or twin-tank arrangements. The engine control module monitors sensor B’s electrical circuit, and this code sets when that circuit has an electrical fault or unusable input.

Common causes

Most likely first.

1. Sensor failed
2. Wiring or connector fault

Symptoms

• Check engine light on
• Hard starting or rough running
• Reduced engine performance
• Fuel economy may worsen

How to diagnose it

1. Check freeze-frame data and live fuel temperature sensor B data for a missing or implausible value; identify sensor B from the vehicle’s service information.
2. Inspect sensor B’s connector and accessible harness for looseness, corrosion, moisture, or physical damage.
3. Use the wiring diagram to check sensor B’s reference or supply, ground, and signal circuit as applicable against the manufacturer’s specification.
4. Test sensor B circuit continuity and shorts, taking care to distinguish its wiring from sensor A’s circuit.
5. If the wiring and connections pass, test fuel temperature sensor B against the manufacturer’s specification and replace it if it fails.

Common fixes

• Reconnect sensor B’s loose connector and repair corroded or damaged terminals.
• Repair an open, shorted, or damaged section of the fuel temperature sensor B wiring.
• Replace fuel temperature sensor B if circuit tests pass and the sensor fails specification.
• Clear the code and confirm the module now receives a plausible sensor B reading.

Can I keep driving?

If the vehicle starts and runs normally, cautious driving to arrange diagnosis is generally reasonable. Avoid extended or demanding trips if hard starting, rough running, or reduced power occurs, since the faulty sensor B input may affect engine control.