Powertrain Controls - ECM/PCM

DTC 14 Chart:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the Signal voltage to the PCM. The PCM applies voltage on CKT 410 to the sensor. When the engine is cold the sensor (thermistor) resistance is high. Therefore the PCM will see high signal voltage. When the PCM sees an ECT signal greater than 140°C (284°F) and the Intake Air Temperature (IAT) is less than 100°C (212°F), DTC 14 will set.

DTC 14 WILL SET WHEN
- DTCs 37 and 38 are not set.
- IAT sensor signal is 100°C (212°F) or less.
- ECT sensor signal is 147°C (297°F) or greater.

ACTION TAKEN (PC will default to)
- With a current DTC 14 set, the PCM will illuminate the Malfunction Indiactor Lamp (MIL) (Service Engine Soon).
- The PCM will use the IAT sensor values in place of the normal ECT sensor values for the first 4.25 minutes of engine operation and then a default value of 90°C (194°F) for the rest of engine

DTC 14 WILL CLEAR WHEN
The fault no longer exists.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. With the ECT sensor or wiring shorted, Tech 1 PCM data parameter will read 147°C or greater.
2. Checking for sensor shorted or CKT 410 shorted. If the parameter value stays at l47°C or greater with the sensor unplugged, the short is in CKT 410 between sensor pin "B" and PCM terminal "B5".

DIAGNOSTIC AIDS
Tech 1 displays engine coolant temperature in degrees. After engine is started, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens.
An intermittent may be caused by rubbed through wire insulation.
Check for:
- CKT 410 for a short to ground.

Intermittent test
With Tech 1, monitor engine coolant temperature while moving related connectors and wiring harness. If the failure is induced, the "engine coolant temperature" display will change. This may help to isolate the location of the malfunction.

Shifted sensor
The "Temperature to Resistance Value" scale may be used to test the engine coolant temperature sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor, which may result in driveability complaints.