Code
P0185
HUMMER
P — Powertrain
Fuel Temperature Sensor 2 Circuit
AI status
Completed
Completed
100%
Causes
- Open or short in the Fuel Temperature Sensor 2 wiring
- Corroded, loose, or damaged connector at the sensor or ECU
- Faulty Fuel Temperature Sensor 2 (thermistor)
- Water or contamination in the fuel or connector
- PCM/ECM internal fault or poor ground at PCM
Symptoms
- Malfunction Indicator Lamp (MIL/Check Engine) illuminated
- Reduced fuel economy or incorrect fuel trims
- Hard start or rough idle, especially when temperature compensation is needed
- Possible increased emissions or failed emissions test
- Intermittent drivability issues if the circuit is intermittent
What to check
- Retrieve freeze frame and live data with a scan tool; verify Fuel Temperature Sensor 2 reading and compare to ambient or other temps
- Visually inspect wiring, harness, and connectors for damage, corrosion, or loose pins
- Check for applicable technical service bulletins (TSBs) for HUMMER models
- Measure sensor connector voltage and resistance with meter and backprobe if needed
- Perform wiggle test on harness while monitoring live data to reveal intermittent faults
Signal parameters
- Sensor type: typically NTC thermistor (resistance decreases as temperature increases)
- Common reference/pull-up: PCM uses an internal pull-up; signal voltage range ~0.1–4.9 V (varies by vehicle)
- Open-circuit indication: very high resistance (often >10 kΩ) or signal near reference rail limit
- Short/low value: resistance very low (often
- Typical cold-to-hot resistance span (generic): several kiloohms at cold to a few hundred ohms at high fuel temps (specs vary by sensor)
Diagnostic algorithm
- Verify the P0185 code and note freeze-frame data with a scan tool. Check for multiple related codes.
- Visually inspect the fuel temperature sensor 2 connector, wiring harness, and fuel rail area for damage, contamination, or loose pins.
- With ignition ON (engine off), backprobe the sensor connector: check for the expected reference voltage (if applicable) and signal voltage. Compare to known ranges or service data.
- Measure sensor resistance with connector unplugged. Compare resistance to ambient temperature reference in service manual or confirm NTC behavior (resistance should drop as sensor is warmed).
- Check continuity between sensor signal pin and PCM pin; measure for short to ground or battery. Repair any short/open found.
- Perform a wiggle/stress test on the harness while monitoring live data to identify intermittent faults. Re-inspect grounds nearby.
- If wiring and connector are good but sensor readings are out of spec, replace the Fuel Temperature Sensor 2. Use OEM or equivalent part.
- After repair, clear codes and verify correct operation using scan tool live data and a test drive. Confirm no return of the code.
- If the fault persists with correct wiring and a known-good sensor, consider PCM diagnosis or reprogramming as a last step.
Likely causes
- Broken or chafed harness between sensor and PCM
- Pin corrosion or bent pins in sensor/connector
- Sensor element failed (thermistor out of spec)
- Short to battery or ground due to rubbed insulation
- Aftermarket work or repairs that disturbed connector or fuel rail
Fault status
Status
Fuel Temperature Sensor 2 circuit fault detected (open/short/out-of-range/intermittent). Inspect sensor, wiring, connectors, and PCM inputs. Replace faulty components as required and confirm with live data.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Repair manuals
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138
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