Fuel and air

P0189 — Fuel Temperature Sensor B Circuit Intermittent

Severity: medium Safe to drive

What P0189 means

The engine control module monitors the signal voltage from fuel temperature sensor B and uses it to adjust fuel delivery for fuel density and temperature. P0189 is set when that signal drops out or jumps outside its expected range from time to time. Because the fault comes and goes, symptoms may not always be present.

Symptoms

  • Check Engine light that comes and goes
  • Rough or unstable idle
  • Hesitation when accelerating
  • Reduced fuel economy
  • Hard or inconsistent starting

Possible causes

  1. Damaged or corroded wiring or connectors in the sensor circuit
  2. Faulty fuel temperature sensor B
  3. Poor ground or loose connector contact
  4. Rarely, a PCM software or calibration error
  5. Rarely, contaminated fuel affecting sensor readings
  6. Internal PCM fault (very unlikely)

How to diagnose

  1. Read freeze frame data to see when the code sets, then clear it and see if it returns
  2. Inspect the sensor connector and harness for corrosion, chafing, or loose terminals
  3. Wiggle the harness and connector with the engine running while watching fuel temperature on a scan tool
  4. Compare the sensor reading with actual fuel temperature and other temperature sensors on a cold engine
  5. Check the 5 V reference and ground at the connector with a multimeter
  6. Measure the sensor resistance and compare to the manufacturer's spec
  7. Test signal wires for opens and shorts back to the PCM
  8. Check for PCM software updates for your vehicle

Common fixes

  • Repair wiring and clean or replace corroded terminals or the connector
  • Replace fuel temperature sensor B
  • Reflash the PCM with the latest manufacturer software
  • Replace the PCM only after ruling out everything else

Questions and answers

Can I drive with a P0189 code?

Usually yes for short trips if the car runs acceptably. Still, don't put off diagnosis, since hesitation and hard starts can develop.

Why does P0189 come and go?

The code indicates an intermittent fault, most often a poor connection or a damaged wire. Vibration and temperature changes make contact come and go.

Where should I start diagnosing P0189?

Begin with a visual check of the fuel temperature sensor connector and wiring. It is the most common cause and costs nothing to inspect.

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.