Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Pinpoint Test DL: Cylinder Head Temperature (CHT) Sensor
Refer to ELECTRONIC ENGINE CONTROLS - 2.7L for schematic and connector information.
Normal Operation and Fault Conditions
The CHT sensor is used to determine the engine coolant temperature. The PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line, with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END value at the same temperature. For example, at 90C (194F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the expected values.
Voltage values calculated for VREF = 5 volts. These values can vary by 15% due to sensor and VREF variations.
Refer to the DTC Fault Trigger Conditions.
DTC Fault Trigger Conditions
| DTC | Description | Fault Trigger Condition |
|---|---|---|
| PCM P0116:00 | Engine Coolant Temperature Sensor 1 Circuit Range/Performance: No Sub Type Information | Sets when the PCM detects the cylinder head temperature value is higher than the calibrated value and could prevent one or more OBD monitors from completing. The PCM runs this logic after an engine off and a calibrated soak period (typically 6 hours). This soak period allows the intake air temperature and the cylinder head temperature to stabilize and not differ by greater than a calibrated value. This DTC sets when all of the following conditions are met: The engine coolant temperature at engine start exceeds the intake air temperature at engine start by greater than a calibrated value, typically 17 deg.C (30 deg.F). The engine coolant temperature exceeds a calibrated value, typically 107 deg.C (225 deg.F). The fuel system, heated oxygen and misfire monitors have not completed. The calibrated time to set this DTC has expired. Make sure the intake air temperature and the engine coolant temperature or cylinder head temperature are similar when the engine is cold. Also make sure the CHT sensor and the actual engine operating temperatures are the same. |
| PCM P0125:00 | Insufficient Coolant Temp For Closed Loop Fuel Control: No Sub Type Information | Sets when the PCM detects the CHT sensor has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting the engine. Compare the thermostat specification to the actual engine coolant temperature using the engine temperature PID (CHT. The temperature reading should be similar when the engine is at a normal operating temperature. |
| PCM P0128:00 | Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature): No Sub Type Information | Sets when the PCM detects the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time. Refer to Thermostat Monitor |
| PCM P017C:00 | Cylinder Head Temperature Sensor "A" Circuit Low: No Sub Type Information | Sets when the PCM detects the CHT circuit is shorted to ground. The DTC P0117 may also be reported when this DTC sets. Either of these Diagnostic Trouble Codes (DTCs) illuminates the MIL. |
| PCM P017D:00 | Cylinder Head Temperature Sensor "A" Circuit High: No Sub Type Information | Sets when the PCM detects a CHT circuit concern is detected. The DTC P0118 may also be reported when this DTC sets. Either of these Diagnostic Trouble Codes (DTCs) illuminate the MIL. |
| PCM P101F:00 | Cylinder Head Temperature Sensor 1 Out Of Self Test Range: No Sub Type Information | This DTC sets when the CHT sensor is out of self-test range. The engine is not at a normal operating temperature. |
| PCM P1285:00 | Cylinder Head Overtemperature Condition: No Sub Type Information | Sets when the PCM detects an engine overheat condition was sensed by the CHT sensor. |
| PCM P1299:00 | Cylinder Head Overtemperature Protection Active: No Sub Type Information | Sets when the PCM detects an engine overheat condition was sensed by the CHT sensor. |
Possible Sources
- CHT sensor circuitry concern
- Base engine concerns
- Engine cooling system concerns
- CHT sensor (6G004)
- PCM (12A650)
Refer to: PINPOINT TESTS DL: CYLINDER HEAD TEMPERATURE (CHT) SENSOR (Gas)
Refer to: PINPOINT TESTS DL: CYLINDER HEAD TEMPERATURE (CHT) SENSOR (Diesel)
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.