P0189
Fuel Temperature Sensor B Circuit Intermittent.
- 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
- 89
- FaultThe specific fault in that area
What it means
P0189 means the engine control unit has detected an intermittent fault in the circuit of fuel temperature sensor B. The sensor signal has dropped out, jumped, or gone out of range for short periods rather than staying faulty. Which fuel system the sensor monitors, and where it is fitted, depends on the model and engine.
Symptoms
- Engine warning light on
- Hard or extended cranking when starting, especially hot or cold
- Intermittent rough running or hesitation
- Slightly poorer fuel economy
- Occasional loss of power or limp mode on some vehicles
- No noticeable symptoms other than the warning light
Possible causes
- Loose, corroded or damaged connector at the fuel temperature sensorlikely
- Chafed, broken or intermittently open or shorted wiring in the sensor circuitlikely
- Failing fuel temperature sensor with an intermittent internal faultlikely
- Poor earth or reference voltage supply shared with other sensorspossible
- Water or fuel contamination in the connector or harnesspossible
- Fault within the control unit or its connector pinsrare
How to diagnose
- Read all stored and pending codes and note any related sensor or fuel system codes.
- Review freeze frame data to see engine temperature, load and speed when the fault set.
- Locate fuel temperature sensor B using the model-specific information, as its position varies by engine and fuel system.
- Inspect the sensor connector and nearby harness for corrosion, bent pins, rubbing, heat damage or fuel contamination.
- With the engine running, view live fuel temperature data and gently wiggle the connector and harness to look for sudden jumps or dropouts.
- Check the sensor resistance against the manufacturer's temperature specification, and compare the reading with the live data.
- Test the sensor reference voltage, signal and earth circuits for continuity, shorts and voltage drop.
- Clear the code and road test, rechecking live data to confirm the signal stays stable.
How to fix
- Clean and secure the connector, or replace it if the terminals are corroded or damaged.
- Repair or replace the damaged wiring section, using proper soldered or crimped and sealed joints.
- Replace the fuel temperature sensor if its readings are erratic or out of specification.
- Repair any earth or supply circuit fault found during testing.
- Dry out and seal the harness and connector after fixing any source of water or fuel ingress.
- Diagnose and repair the control unit or its connector only after all circuit and sensor faults are ruled out.
Can I keep driving?
Low severity
The car can usually be driven while you arrange a repair, as the fault is intermittent and often has little effect. If it starts to run poorly, struggle to start or enter limp mode, have it checked sooner.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.