Pinpoint Test DL: Cylinder Head Temperature (CHT) Sensor: Introduction: Notes

On applications that do not use an ECT sensor, the CHT sensor is used to determine the engine coolant temperature in place of the ECT sensor. To cover the entire temperature range of both the CHT and ECT sensors, 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 voltage at the same temperature. For example, at 90 °C (194 °F) the voltage could read either 0.60 volt or 3.71 volts. REFER to the  CYLINDER HEAD TEMPERATURE SENSOR EXPECTED VALUES   table for the temperature to voltage expected values  .

Fig 1: Cylinder Head Temperature (CHT) Sensor Temperature/Voltage Graph

Courtesy of FORD MOTOR CO.

Voltage values calculated for VREF = 5 volts. These values can vary by 15% due to sensor and VREF variations  .