Diagnostic Test

1) VERIFY DTC B1002-A/C SWITCH REQUEST INPUT CIRCUIT HIGH IS ACTIVE
Turn the ignition on.

With the scan tool, erase CCN DTCs.

Turn the ignition off, wait 10 seconds, and turn the ignition on.

With the scan tool, read CCN DTCs.

Does the scan tool display active: B1002-A/C SWITCH REQUEST INPUT CIRCUIT HIGH?

Yes
1. Go To 2).
No
1. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Repair as necessary.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
2) CHECK THE (C105) HVAC MUX CONTROL CIRCUIT VOLTAGE AT A/C HEATER CONTROL C1 HARNESS CONNECTOR

Fig 1: Measuring Voltage Of HVAC MUX Control Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the A/C Heater Control C1 harness connector.

Turn the ignition on.

Measure the voltage of the (C105) HVAC MUX Control circuit.

What is the voltage?

Below 4.8 Volts
1. Go To 3).
4.8 to 5.2 Volts
1. Go To 4).
Above 5.2 Volts
1. Go To 6).
3) CHECK THE (C105) HVAC MUX CONTROL CIRCUIT FOR AN OPEN

Fig 2: Measuring Resistance Of HVAC MUX Control Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Instrument Cluster C4 harness connector.

Measure the resistance of the (C105) HVAC MUX Control circuit between the A/C Heater Control C1 harness connector and the Instrument Cluster C4 harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Replace the Instrument Cluster (CCN) in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
No
1. Repair the (C105) HVAC MUX Control circuit for an open.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
4) CHECK THE (C955) HVAC MUX RETURN CIRCUIT OPERATION

Fig 3: Probing HVAC MUX Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Using a 12-volt test light connected to 12 volts, back probe the (C955) HVAC MUX Return circuit in the A/C Heater Control C1 harness connector.

Does the test light illuminate brightly?

Yes
1. Replace the A/C-Heater Control in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
No
1. Go To 5).
5) CHECK THE (C955) HVAC MUX RETURN CIRCUIT FOR AN OPEN

Fig 4: Measuring Resistance Of HVAC MUX Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance of the (C955) HVAC MUX Return circuit between the A/C Heater Control C1 harness connector and the Instrument Cluster C4 harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Replace the Instrument Cluster in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
No
1. Repair the (C955) HVAC MUX Return circuit for an open.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
6) CHECK THE (C105) HVAC MUX CONTROL CIRCUIT FOR A SHORT TO VOLTAGE

Fig 5: Measuring Voltage Of HVAC MUX Control Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Instrument Cluster C4 harness connector.

Turn the ignition on.

Measure the voltage of the (C105) HVAC MUX Control circuit.

Is the voltage above 0.2 volts?

Yes
1. Repair the (C105) HVAC MUX Control circuit for a short to voltage.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .
No
1. Replace the Instrument Cluster (CCN) in accordance with the Service Information.
2. Perform BODY VERIFICATION TEST - VER 1. Refer to BODY VERIFICATION TEST - VER 1 .