Monitoring Procedures

DIAGNOSTIC CODES: P0116, P0117, P0118, P0125

Monitoring Procedure
The range is checked for values outside the limits.

A "time-to-warm-up" test will check that the sensor is responding to the rise in coolant temperature in the running engine and ensure that closed loop fuelling is entered within a specified time limit. Another test will check or abnormal falls in temperature once the temperature rise has been detected.

If these tests are not passed then a fault event is recorded and if the count exceeds a given limit then a fault is registered.

While fault counting is in progress a back-up value of coolant temperature will be supplied and when faults are present a default value of coolant temperature will be supplied. Coolant temperature default value will depend on intake air temperature value. The strategy will report to the Diagnostic Status Manager when all the tests have been performed once; the DSM will then decide whether to store a fault code and illuminate the MIL Lamp.

Interface Between ECM And ECTS:

Engine Coolant Temperature Sensor (ECT), Diagnostic Code P0116
ECT Circuit Range/Performance - Falling Temperature. A falling temperature test will check for abnormal falls in temperature once a temperature rise has been detected.

Possible causes:
- Thermostat seized open
- ECT connector high resistance when hot
- Intermittent high resistance - ECT harness
- ECT-changing output

ECT Circuit Low Input, Diagnostic Code P0117
The output of the ECT sensor is checked for values outside limits:
- High temperature limit 18O °F
- Low temperature limit -39 °C

Possible causes:
- Temperatures under -5O °C
- ECT disconnected
- ECT harness open circuit or high resistance
- ECT signal short circuit to battery voltage
- ECT fault - open circuit or high resistance
- ECM interface circuit fault

ECT Circuit High Input, Diagnostic Code P0118
The output of the ECT sensor is checked for values outside limits.

Possible causes:
- Temperatures very hot - engine boiled
- ECT harness wires short circuit to ground
- ECT fault - low resistance
- ECM interface circuit fault

Excessive Time to Enter Closed Loop Fuel Control, Diagnostic Code P0125
A test will check that the sensor responds in 5 seconds to a rise in coolant temperature to 20 °C.

Possible causes:
- Low ambient temperature
- Thermostat seized open
- ECT harness - high resistance
- ECT high resistance
- ECM interface circuit