Powertrain Controls - ECM/PCM

DTC 15 Engine Coolant Temperature (ECT) Sensor Circuit High (Low Temperature Indicated):

Engine Coolant Temperature (ECT) Circuit Low (High Temperature Indicated):

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is a thermistor that controls signal voltage to the Powertrain Control Module (PCM). When the engine is cold, the sensor resistance is high, therefore the PCM will see high signal voltage. As the engine warms, the sensor resistance becomes less and the voltage drops.

DTC 15 WILL SET WHEN
^ Engine coolant temperature less than -36°C (-33°F).
^ Engine running for at least 8 minutes.

ACTION TAKEN (PCM will default to)
The PCM will default to 77°C (171°F) and fast idle.

DTC 15 WILL CLEAR WHEN
The fault condition(s) no longer exist.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test determines if DTC 15 is a hard failure or an intermittent condition.
2. This test will determine if CKT 410 is shorted to ground.
3. This test will determine if CKT 410 is open or for a faulty PCM.

DIAGNOSTIC AIDS
Check harness routing for a potential short to ground. After engine is started, the ECT temperature should rise steady to about 85°C (185°F). The default value will flash intermittently on the data screen.