P1285 Code MERCURY Possible Causes
- Engine overheated
- Low engine coolant level
- Faulty Cylinder Head Temperature (CHT) sensor
- Cylinder Head Temperature sensor harness is open or shorted
- Poor electrical connection in the Cylinder Head Temperature sensor circuit
How is the MERCURY P1285 Code Repair Performed?
Start by checking the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
What are the Possible Symptoms of MERCURY P1285 Code?
- Engine Light On (or Service Engine Soon Warning Light)
What is the Meaning of MERCURY P1285 Code?
The Cylinder Head Temperature (CHT) sensor is a thermistor device where the resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases and the resistance increases as the temperature decreases. The variable resistance affects the voltage drop across the sensor terminals and provides electrical signals to the Powertrain Control Module (PCM) corresponding to the temperature.
The CHT sensor is installed in the aluminum cylinder head and measures the metal temperature. The CHT sensor can provide comprehensive engine temperature information and can be used to infer coolant temperature. If the CHT sensor reports an overheating condition to the PCM, the PCM initiates a fail-safe cooling strategy based on the CHT sensor information. A cooling system issue such as low coolant level or coolant loss can cause overheating. This could damage major engine components. By using both the CHT sensor and the fail-safe cooling strategy, the PCM prevents damage by allowing engine air cooling and backup capability.
The Diagnostic Trouble Code (DTC) indicates detected cylinder head overheating, meaning an engine overheating condition has been detected by the Cylinder Head Temperature sensor.