Code
P0115
HUMMER
P — Powertrain
Engine Coolant Temperature (ECT) Sensor Circuit
AI status
Completed
Completed
100%
Causes
- Open or short in ECT sensor wiring
- Corroded, loose or water-damaged sensor connector
- Failed/shorted ECT (thermistor) sensor
- Poor ground or missing reference voltage from PCM
- Coolant intrusion in connector or sensor
- Faulty PCM/ECM (rare)
Symptoms
- Malfunction Indicator Lamp (MIL/Check Engine) illuminated
- Incorrect coolant temperature reading on dash or scan tool
- Extended cranking or hard cold start
- Rough idle and poor drivability until engine warms
- Reduced fuel economy or increased emissions
- Cooling fan or thermostat control issues
What to check
- Read freeze-frame and live data with a scan tool — monitor ECT temperature PID and compare to ambient/engine state
- Confirm presence of stored freeze-frame and whether code is continuous or intermittent
- Visually inspect ECT sensor connector and wiring for damage, corrosion, or coolant contamination
- Backprobe sensor connector to verify reference voltage and signal while key ON and engine running
- Measure sensor resistance (terminals disconnected) at known ambient temperature and compare to spec
- Check continuity of signal and ground circuits to PCM; check for shorts to 12V or ground
Signal parameters
- Typical ECM reference voltage: ~5.0 V (varies by model)
- Sensor signal voltage (approx): cold engine ~3.5–5.0 V ; warm engine ~0.2–1.5 V (depends on sensor/engine)
- Typical NTC resistance examples (varies by sensor): ~2.5–4.0 kΩ at 20°C (68°F) ; ~200–500 Ω at 80°C (176°F)
- Expect a steadily changing voltage/temperature reading as engine warms; jumps or stuck values indicate circuit or sensor fault
- Exact values vary by model year and sensor — confirm HUMMER service specs before replacement
Diagnostic algorithm
- Retrieve codes and live data with a scan tool. Note freeze-frame conditions and whether ECT reading is plausible given ambient temp.
- Visually inspect sensor, connector and harness for obvious damage, corrosion or coolant contamination. Repair any physical issues.
- With ignition ON (engine off), backprobe sensor connector: verify ECM reference voltage (≈5V) and sensor signal voltage. Record values.
- Start engine and monitor ECT PID while warming. Look for expected change from cold to operating temperature. If signal is erratic or stuck, continue.
- With sensor disconnected and engine cool, measure sensor resistance at ambient temperature. Compare to OEM spec chart (if not available, compare to typical NTC behavior: higher R when cold, lower when hot).
- Check continuity from sensor connector to PCM pin; check for shorts to battery and chassis ground. Repair wiring faults as found.
- If wiring and connectors are good but sensor is out of resistance/spec range or signal remains incorrect, replace the ECT sensor.
- After repair, clear codes, re-run readiness and test drive to verify code does not return and ECT readings track normal warm-up.
- If problem persists after replacing sensor and wiring confirmed good, consider PCM input circuitry diagnosis or replacement per factory procedures.
Likely causes
- Disconnected or corroded ECT connector at sensor
- Broken wire at harness chafe point near engine or firewall
- ECT sensor internal failure (thermistor out of spec)
- Short to battery voltage or short to ground on sensor signal circuit
- Contaminated connector pins from coolant or corrosion
Fault status
Status
P0115 indicates an electrical fault in the engine coolant temperature sensor circuit. It can cause incorrect temperature readings and affect drivability; inspection of the sensor, wiring and connectors is recommended.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
HUMMER
-
HUMMER: 2009
-
HUMMER: 2008
-
HUMMER: 2007
-
HUMMER: 2005
-
HUMMER: 2004
-
HUMMER: 2000
-
HUMMER: 1999
-
HUMMER: 1994
-
HUMMER: 1993
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email