Diagnostic Test

1) ACTIVE DTC
NOTE: Diagnose any CAN - C Communication DTCs before continuing.

Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes
1. Go To step 2).
No
1. Refer to INTERMITTENT CONDITION .
2. Perform POWERTRAIN VERIFICATION TEST .
2) (G31) AAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Fig 1: Checking Ambient Air Temperature Sensor Signal Circuit Shorted To Battery Voltage
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C2 FCM harness connector.

Disconnect the AAT Sensor harness connector.

NOTE: Visually inspect both the component and the FCM connectors. Look for damaged, partially broken wires, and backed out or corroded terminals.

Ignition on, engine not running.

Measure the voltage on the (G31) AAT Signal circuit in the AAT Sensor harness connector.

Is the voltage above 5.2 volts?

Yes
1. Repair the short to voltage in the (G31) AAT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 3).
3) AAT SENSOR VOLTAGE ABOVE 4.6 VOLTS
Turn the ignition off.

Connect the C2 FCM harness connector.

Ignition on, engine not running.

With a scan tool, read the AAT voltage.

Is the voltage above 4.6 volts?

Yes
1. Go To step 4).
No
1. Go To step 7).
4) AAT SENSOR

Fig 2: Identifying Ambient Air Temperature Sensor Connector Terminals
Courtesy of DAIMLERCHRYSLER CORP.

Connect a jumper wire between the (G31) AAT Signal circuit and the (G931) Sensor ground circuit in the AAT Sensor harness connector.

With a scan tool, read the AAT voltage.

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

Yes
1. Replace the AAT Sensor.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 5).
  NOTE: Remove the jumper wire before continuing.
5) (G31) AAT SIGNAL CIRCUIT OPEN

Fig 3: Checking Ambient Air Temperature Sensor Signal Circuit For Open
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C2 FCM harness connector.

Measure the resistance of the (G31) AAT Signal circuit from the AAT Sensor harness connector to the C2 FCM harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Go To step 6).
No
1. Repair the open in the (G31) AAT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
6) (G931) SENSOR GROUND CIRCUIT OPEN

Fig 4: Checking Ambient Air Temperature Sensor Ground Circuit For Open
Courtesy of DAIMLERCHRYSLER CORP.

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
1. Go To step 9).
No
1. Repair the open in the (G931) Sensor ground circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
7) (G31) AAT SIGNAL CIRCUIT SHORTED TO GROUND

Fig 5: Checking Ambient Air Temperature Sensor Signal Circuit Shorted To Ground
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C2 FCM harness connector.

Measure the resistance between ground and the (G31) AAT Signal circuit in the AAT Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the short to ground in the (G31) AAT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 8).
8) (G31) AAT SIGNAL CIRCUIT SHORTED TO THE (G931) SENSOR GROUND CIRCUIT

Fig 6: Checking AAT Sensor Signal Circuit Shorted To Ground
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between the (G31) AAT Signal circuit and the (G931) Sensor ground circuit in the AAT Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Repair the short between the (G931) Sensor ground circuit and the (G31) AAT Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 9).
9) FRONT CONTROL MODULE
NOTE: Before continuing, check the FCM 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 BODY VERIFICATION TEST - VER 1 .
No
1. Replace the Front Control Module per Service Information.
2. Perform BODY VERIFICATION TEST - VER 1 .