Code
P0189
GWM
P — Powertrain
- Fuel temperature sensor B fault
Views:
UK: 17
EN: 17
RU: 17
AI status
Completed
Completed
100%
Causes
- Damaged or corroded connector at fuel temperature sensor B
- Broken, chafed or shorted wiring/harness to the sensor
- Faulty fuel temperature sensor B (thermistor)
- Poor ground or reference supply to the sensor circuit
- Water/fuel contamination or internal fuel tank damage affecting the sensor
- Faulty ECM or connector (rare)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated with P0189 stored
- Erratic or implausible fuel temperature readout on scan tool (very high, very low or fixed value)
- Possible hard starting or extended cranking in cold conditions
- Suboptimal fuel trim, reduced fuel economy or slightly rough idle under some conditions
- Reduced performance or limp mode on some vehicles (rare)
What to check
- Connect a scan tool and record freeze-frame data and live fuel temperature B PID
- Compare Fuel Temp B reading to Fuel Temp A (if present) and ambient/engine temperatures
- Visually inspect sensor connector and wiring for damage, corrosion, pin push-out or fuel intrusion
- Wiggle test harness while watching live data to try to reproduce the fault (check for intermittent)
- Backprobe sensor connector and measure signal voltage with key on/engine off and while engine running (use proper backprobe technique)
- Measure sensor resistance at connector (with harness disconnected) and compare with known thermistor behavior (resistance changes with temperature)
Signal parameters
- Sensor type: typically an NTC thermistor (temperature-dependent resistor) mounted in the fuel system
- Typical interface: 2 or 3 wires (signal, reference 5V or pull-up, and ground) depending on vehicle
- Expected voltage range at ECM: generally within 0.1–4.9 V depending on temperature and manufacturer's design (consult factory spec for exact values)
- Expected behavior: resistance decreases as temperature rises (NTC). Exact ohms vs temperature vary by sensor model — compare to factory chart when available
Diagnostic algorithm
- Retrieve and record freeze-frame and permanent data with a diagnostic scanner; note any related codes.
- Inspect the sensor and harness visually for corrosion, fuel contamination, bent pins or damage. Repair obvious damage.
- With ignition ON, backprobe the sensor connector and verify reference voltage (if present) and ground continuity. Reference typically ~5V or pull-up; ground should be good. Do not short pins.
- With harness disconnected, measure sensor resistance at vehicle connector and observe change while warming the sensor (by hand or applying warm air) to confirm thermistor response. Compare to specification if available.
- With harness connected, monitor live PID while performing wiggle test of wiring and connector to detect intermittent faults.
- Check for short to power or ground: disconnect harness and measure resistance from signal wire to chassis ground and to battery +. Open/short indicates wiring fault.
- If wiring and connectors are good but sensor readings are out-of-range or do not change with temperature, replace fuel temperature sensor B.
- If sensor and wiring test good, verify ECM input and outputs for the circuit; inspect ECM connector pins and repair as needed. Replace ECM only after eliminating harness and sensor faults.
- After repairs, erase codes, perform a functional test/drive cycle and confirm code does not return.
Likely causes
- Connector corrosion or loose connection at the sensor
- Open or short in wiring harness between sensor and ECM
- Failed sensor (thermistor out of spec)
- Poor ground or reference voltage at the sensor
Fault status
Status
P0189 — Fuel Temperature Sensor B circuit fault detected (open/short/intermittent or out-of-range). MIL illuminated. Inspect sensor, wiring and connectors.
Repair difficulty: Medium
Diagnostic time: 0.5-3.0 hours
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