Engine Coolant Temperature Sensor Circuit Intermittent (GM)
What does P1117 mean?
The P1117 code means the vehicle's onboard diagnostic system has detected: Engine Coolant Temperature Sensor Circuit Intermittent (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Erratic temperature gauge readings
- Cooling fans turning on and off randomly
- Inconsistent idle quality
- Occasional hard starting
Probable Causes (Ranked by Likelihood)
- Intermittent ECT sensor failure Very High
- Loose or corroded ECT sensor connector High
- Chafed or frayed wiring in ECT sensor circuit Moderate
- Poor ground connection at ECT sensor Moderate
- PCM connector issue Low
Step-by-Step Diagnostic Procedure
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Monitor ECT sensor data on a scan tool for sudden jumps or dropouts
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Wiggle test the ECT sensor connector and wiring while watching live data
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Inspect wiring harness for chafing against engine components
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Clean and tighten the ECT sensor connector and ground points
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Replace the ECT sensor if intermittent readings persist
Frequently Asked Questions
Why does my temperature gauge jump around with P1117?
P1117 indicates an intermittent electrical connection in the coolant temperature sensor circuit. The jumping gauge reflects the sensor signal cutting in and out, sending erratic temperature readings to the PCM and dashboard.
Can P1117 cause overheating?
P1117 itself does not cause overheating, but it can prevent the cooling fans from operating correctly. If the fans do not turn on when needed, the engine could overheat. Monitor your temperature closely until repaired.
Is the ECT sensor easy to replace?
Yes. The ECT sensor is typically held in by threads and a single electrical connector. Drain some coolant below the sensor level, unplug it, unscrew the old sensor, and install the new one. The job takes about 30 minutes.