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

This pinpoint test is intended to diagnose the following:

• CHT sensor (6G004)
• harness circuits: CHT, VREF, and SIGRTN
• powertrain control module (PCM) (12A650)

On applications that do not use an engine coolant temperature (ECT) sensor, the CHT sensor is used to determine the engine coolant temperature. 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 Fig 1 and CYLINDER HEAD TEMPERATURE SENSOR EXPECTED VALUES  for the temperature to voltage expected values.

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

Fig 1: Cylinder Head Temperature Sensor Voltage And Resistance Characteristic Graph

Courtesy of FORD MOTOR CO.

Fig 2: Cylinder Head Temperature (CHT) Sensor Connector

Courtesy of FORD MOTOR CO.

For PCM connector views or reference values, refer to REFERENCE VALUES .