Dodge Durango (HB). Manual — part 787
P0128-THERMOSTAT RATIONALITY (CONTINUED)
7.
SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
NOTE: Visually inspect both the component and the PCM connec-
tors. Look for damage, partially broken wires and backed out or
corroded terminals
Turn the ignition off.
Disconnect the applicable Temperature Sensor harness connector.
Disconnect the C2 FCM harness connector and the C2 PCM harness
connector.
Ignition on, engine not running.
Measure the voltage on the (K2) ECT Signal circuit and the (G31) AAT
Signal circuit at the appropriate Temperature Sensor harness connec-
tor.
Is the voltage above 5.2 volts?
Yes
>> Repair the short to battery voltage in the Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 8
HB
ENGINE ELECTRICAL DIAGNOSTICS
9 - 147
P0128-THERMOSTAT RATIONALITY (CONTINUED)
8.
TEMPERATURE SENSOR
Turn the ignition off.
Connect the C2 FCM harness connector and the C2 PCM harness
connector.
Connect a jumper wire across the ECT and AAT Sensor harness con-
nectors.
Ignition on, engine not running.
With a scan tool, read the Temperature Sensor voltage.
Does the voltage start at 5.0 volts and drop below 1.0 volt when
the jumper wire is installed?
Yes
>> Replace the appropriate Temperature Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 9
NOTE: Disconnect the jumper wire before continuing.
9 - 148
ENGINE ELECTRICAL DIAGNOSTICS
HB
P0128-THERMOSTAT RATIONALITY (CONTINUED)
9.
SIGNAL CIRCUIT OPEN
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 Sensor Signal circuit from the
ECT Sensor harness connector to the appropriate terminal of special
tool #8815.
Measure the resistance of the (G31) AAT Sensor Signal circuit from
the AAT Sensor harness connector to the C2 FCM harness connector.
Is the resistance below 5.0 ohms?
Yes
>> Go To 10
No
>> Repair the open in the Sensor Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
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ENGINE ELECTRICAL DIAGNOSTICS
9 - 149
P0128-THERMOSTAT RATIONALITY (CONTINUED)
10.
SENSOR GROUND CIRCUIT OPEN
Measure the resistance of the (K900) Sensor ground circuit from the
appropriate Temperature Sensor harness connector to the appropriate
terminal of special tool #8815.
Measure the resistance of the (G931) Sensor ground circuit from the
AAT Sensor harness connector to the C2 FCM harness connector.
Is the resistance below 5.0 ohms?
Yes
>> Go To 11
No
>> Repair the open in the Sensor ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)
9 - 150
ENGINE ELECTRICAL DIAGNOSTICS
HB
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