Diagnostic Test

1) ECT SENSOR VOLTAGE ABOVE 4.98 VOLTS
Ignition on, engine not running.

With a scan tool, read the ECT voltage.

Is the voltage above 4.98 volts?

Yes
1. Go To 2).
No
1. Refer to INTERMITTENT CONDITION .
2. Perform POWERTRAIN VERIFICATION TEST .
2) ECT SENSOR

Fig 1: Checking Engine Coolant Temperature Sensor Signal Circuit & Ground Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the ECT harness connector.

Connect a jumper wire between the (K2) ECT Signal circuit and the (K900) Sensor ground circuit in the ECT harness connector.

Ignition on, engine not running.

With a scan tool, read ECT voltage.

Is the voltage below 1.0 volt with the jumper wire installed?

Yes
1. Replace the ECT Sensor.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To 3).
  NOTE: Remove the jumper wire before continuing.
3) (K2) ECT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Fig 2: Checking Engine Coolant Temperature Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the PCM harness connectors.

Ignition on, engine not running.

Measure the voltage on the (K2) ECT Signal circuit in the ECT Sensor harness connector.

Is voltage present?

Yes
1. Repair the short to battery voltage in the (K2) ECT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To 4).
4) (K2) ECT SIGNAL CIRCUIT OPEN

Fig 3: Checking Engine Coolant Temperature Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (K2) ECT Signal circuit from the ECT Sensor harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes
1. Go To 5).
No
1. Repair the open in the (K2) ECT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
5) (K900) SENSOR GROUND CIRCUIT OPEN

Fig 4: Checking Engine Coolant Temperature Sensor Ground Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance of the (K900) Sensor ground circuit from the ECT Sensor harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes
1. Go To 6).
No
1. Repair the open in the (K900) Sensor ground circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
6) PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes
1. Repair as necessary.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Replace and program the Powertrain Control Module per Service Information.
2. Perform POWERTRAIN VERIFICATION TEST .