Powertrain Controls - ECM/PCM

Diagnostic Trouble Code (DTC) 15:

Engine Coolant Temperature (ETC) Sensor Circuit:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor uses a thermistor to control the signal voltage to the Powertrain Control Module (PCM). The PCM applies a voltage on CKT 410 to the sensor. When the engine coolant is cold, the sensor (thermistor) resistance is high, therefore the PCM signal voltage will be high. As the engine coolant warms, the sensor resistance becomes less, and the PCM voltage drops. At normal engine operating temperature (85°C - 95°C or 185°F - 203°F), the voltage should measure about 1.5 to 2.0 volts at the PCM.

DIAGNOSTIC TROUBLE CODE (DTC) 15 WILL SET WHEN
The PCM indicates engine coolant temperature signal -40°C (-40°F) or lower for 2 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate, and Torque Converter Clutch (TCC) will apply early.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Monitoring ECT will determine if the fault is a hard failure or an intermittent condition.
2. This test simulates a DTC 14. If the PCM recognizes the low signal voltage, (high temperature) and the Tech 1 displays 130°C (266°F) or above, the PCM and wiring are OK.
3. This test will determine if CKT 410 is open. There should be 5 volts present at sensor connector, if measured with a DVOM.

DIAGNOSTIC AIDS
A Tech 1 scanner displays engine coolant temperature in degrees Celsius and Fahrenheit. After engine is started, the temperature should rise steadily, reach normal operating temperature, and then stabilize when the thermostat opens.

A faulty connection, or an open in CKT 410 or 470, will result in a DTC 15.

If DTC 21 or 59 is also set, check CKT 470 for faulty wiring or connections. Check terminals at sensor for good contact. Refer to Diagnosis by Symptom/Intermittents. - Intermittent Malfunctions