P1290 - FAULT CODE - OBD2

P1290 FORD, LINCOLN, MAZDA, MERCURY: CYLINDER HEAD TEMPERATURE SENSOR SIGNAL BELOW  SELF-TEST RANGE

The CHT (Cylinder Head Temperature) is a sensor located in the cylinder head, not connected to a coolant line. This device provides a voltage signal to the PCM (Powertrain Control Module), which informs it about the actual cylinder head temperature.

When the temperature detected by the CHT Sensor is higher than 126 ° C, the PCM prevents the operation of 4 fuel injectors at the same time. The PCM alternates the four disabled injectors every 32 engine cycles. The cylinders that are prevented from receiving fuel injection function as air pumps and through this help to lower engine temperatures. In the event that the temperature exceeds 154°C, the PCM proceeds to deactivate the fuel injectors until the engine temperature is lowered below 154°C.

The P1290 OBDII fault code is set on Ford, Lincoln, Mazda, and Mercury vehicles when, after performing various self-tests, the PCM detects that the cylinder head temperature is below the expected values.

• Check Engine Lamp illuminated.
• Significant increase in engine temperatures.

P1290 OBD2 diagnostic code is set for one of the following reasons:

• The engine may have an overheating condition due to a lower than necessary coolant level.
• The thermostat may be damaged.
• The CHT Sensor circuit wiring may be faulty.
• The Cylinder Head Temperature Sensor could be in poor condition.

The steps to follow to troubleshoot the DTC P1290 OBDII code are as follows:

• Consult the TSB.
• Check the engine for excessively low coolant levels. Look for leaks or contamination in the coolant and make corrections as needed.
• Inspect all Cylinder Head Temperature Sensor wiring harnesses. Look for damage caused by corrosion, wear, or burns and if such conditions are found, make repairs as required.
• Check the CHT Sensor circuit for poor or bad connections. If conditions exist that could cause an open circuit, make the appropriate repairs.
• Check the thermostat for proper operation. Follow the manufacturer's recommendations to perform a diagnosis of the thermostat and if you detect deficiencies in the thermostat, replace it.