P1285 FORD, LINCOLN, MAZDA, MERCURY: CYLINDER HEAD OVERTEMPERATURE CONDITION
POST UPDATED IN January, 2023
P1285 Code failures by brands
Description of DTC code P1285
The CHT sensor (Cylinder Head Temperature) is a thermistor device whose resistance varies with temperature. This resistance decreases as the temperature increases and the resistance increases if the temperature is low. These changes in resistance directly affect the voltage drop across the terminals of the CHT sensor, which is provided to the PCM (Powertrain Control Module) as temperature information.
The Cylinder Head Temperature Sensor is located in the aluminum cylinder head and basically its function is to measure the temperature of the metal. It can send complete engine temperature information and can be used to infer the coolant temperature. In the event that the CHT sensor reports an overheat condition to the PCM, the PCM will initiate a fail-safe cooling strategy based on the sensor data.
When the DTC P1285 OBDII code is set, it is because the PCM has received information from the Cylinder Head Temperature Sensor indicating an engine overheat condition.
Symptoms of fault code P1285
- Check Engine lamp illuminated.
- Significant increase in engine temperatures.
Causes of OBD2 P1285
The factors for which the P1285 OBD2 fault code is set up are:
- Engine coolant level may not be sufficient.
- Cylinder Head Temperature Sensor wires or connectors may have damage.
- The CHT sensor may be faulty.
Possible solutions of the DTC code P1285
The corresponding steps to troubleshoot the P1285 OBDII diagnostic code are:
- As a first step consult the Technical Service Bulletins.
- Check the available amount of engine coolant and check if the coolant level is within the proper levels. If you discover a level below the required level, make the appropriate corrections.
- Inspect all CHT Sensor wiring and circuit connections. Look for deficiencies caused by wear or corrosion and if such conditions are found, make repairs.
- Measure the Cylinder Head Temperature Sensor circuit voltages and verify that this circuit is not open or shorted. Also, follow the manufacturer's recommendations to verify the integrity of the sensor. Correct it as applicable.
