Code
P0188
GWM
P — Powertrain
- High Temperature Sensor B
Views:
UK: 3
EN: 6
RU: 6
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in the Fuel Temperature Sensor B circuit
- Faulty Fuel Temperature Sensor B (NTC thermistor) or connector
- Corroded, loose, or contaminated electrical connector or pins
- Short to battery voltage (sensor signal wire) or to another hot circuit
- Failed or intermittent PCM/ECM input or reference circuit
- Aftermarket wiring, recent repairs, or fuel system service left connector damaged
Symptoms
- Check Engine Light (MIL) on
- Reduced engine performance or poor fuel trim (may be mild)
- Hard starting or poor cold/hot running behavior in some conditions
- Possible increased emissions or fuel consumption
- Stored freeze-frame data showing high fuel temp reading or erratic values
What to check
- Retrieve freeze frame and live data: monitor fuel temperature B and compare to ambient/engine temps
- Scan for related codes (other temp or fuel sensor faults) and note pending codes
- Visual inspection of sensor, harness, and connector for damage, corrosion, water ingress, or loose pins
- Backprobe sensor connector to measure signal voltage and reference voltage with ignition ON
- Measure sensor resistance at known temperatures (remove sensor if necessary)
- Check PCM ground(s) and connector for signs of damage or corrosion
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature rises)
- Expected signal: voltage range from ~0.1–4.9 V depending on temperature and vehicle design (verify with manufacturer data)
- Typical resistance examples (vehicle-specific): hundreds to thousands of ohms across ambient range — consult OEM specs before replacement
- Reference supply: normally a stable ignition-switched or sensor reference voltage from PCM (often 5 V) and a PCM ground
Diagnostic algorithm
- Read freeze-frame, pending codes, and live data. Confirm P0188 is active and observe fuel temp B value.
- Perform a visual inspection of the sensor, connector and harness for damage, corrosion, or water entry. Repair any obvious issues.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage from PCM and good ground. If reference or ground is missing, suspect PCM harness or PCM.
- Measure the sensor signal voltage and compare to expected for ambient temperature. If signal is at or near battery voltage, suspect short-to-battery; if signal is open or > expected high threshold, suspect open or high circuit.
- Remove sensor and measure its resistance at known temperature (room temp). Compare resistance to OEM specification. Replace sensor if out of spec.
- If wiring appears suspect, perform continuity checks to PCM and check for short-to-voltage or short-to-ground. Repair/replace damaged wiring or connectors.
- After repair or replacement, clear codes and perform a test drive or run live data to confirm stable, correct fuel temperature readings and that code does not return.
- If wiring and sensor check good but code persists, perform PCM input circuit tests per OEM service manual or consult a dealer-level technician for PCM diagnosis.
Likely causes
- Damaged sensor harness or rubbing through causing short-to-voltage
- Connector corrosion at the sensor or PCM
- Failed fuel temperature sensor (internal open or high resistance)
- Poor PCM ground or damaged PCM input circuit
Fault status
Status
Fuel Temperature Sensor B Circuit High — sensor or circuit is reporting an unexpectedly high temperature/voltage. Check sensor, wiring, connector, and PCM input.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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