Fuel and air

P0185 — Fuel Temperature Sensor B Circuit Malfunction

Severity: medium Safe to drive

What P0185 means

The engine control module reads the voltage from fuel temperature sensor B, whose resistance changes as the fuel warms up. It uses this to fine-tune fuel delivery and injection timing. P0185 sets when the signal voltage falls outside the expected range, pointing to an open, a short, or a failed sensor.

Symptoms

  • Check Engine light on
  • Worse fuel economy
  • Rough or unstable idle
  • Hesitation during acceleration
  • Hard starting, hot or cold

Possible causes

  1. Failed fuel temperature sensor B
  2. Corroded or damaged sensor connector
  3. Open or chafed wiring in the sensor circuit
  4. Signal wire shorted to ground or to voltage
  5. PCM input circuit fault (uncommon)

How to diagnose

  1. Scan for codes, review freeze frame data and look for other fuel system codes
  2. Compare the fuel temperature reading in live data with other engine temperatures on a cold engine; they should be close
  3. Inspect the sensor connector and harness for corrosion, moisture, or rubbing damage
  4. Unplug the sensor and check for reference voltage (usually about 5 V) and ground at the harness
  5. Measure sensor resistance and compare it to the spec for your vehicle
  6. Test the signal and ground wires back to the PCM for opens and shorts
  7. If the sensor and wiring are good, check the PCM and its connector

Common fixes

  • Replace fuel temperature sensor B
  • Clean the terminals or replace the connector
  • Repair or replace the damaged wiring
  • Repair or reprogram the PCM only if it is confirmed faulty

Questions and answers

Can I drive with a P0185 code?

Usually yes, for a short time until you can get it checked. The PCM runs on fallback values, so expect possible poor mileage and uneven running.

What most often causes P0185?

Most often it is the sensor itself or its connector and wiring: corrosion, an open or a short. A faulty PCM is rare.

How do I clear P0185?

Fix the underlying fault first, then erase the code with a scan tool. If the problem remains, the code will return.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.