Diagnostic Test

1) CHECK FOR ACTIVE DTC
With the scan tool, read the active DTCs.

Erase the DTCs.

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

With the scan tool, read the active DTC's.

Does the scan tool display this DTC as active?

Yes
1. Go To 2).
No
1. If the DTC is stored, check for an intermittent condition. Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals, and repair any obvious problems.
2. Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1) .
2) CHECK THE (W527) VSIM CAN B BUS (+) CIRCUIT FOR AN OPEN

Fig 1: Measuring Resistance Of VSIM CAN B Bus (+) Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Multi-Purpose Module (Police And Taxi Interface Module-PTIM) C1 harness connector.

Disconnect the Multi-Purpose Module (Police And Taxi Interface Module-PTIM) 24 way harness connector (aftermarket light/siren controller side).

Measure the resistance of the (W527) VSIM CAN B Bus (+) circuit between the Multi-Purpose Module (Police And Taxi Interface Module-PTIM) C2 connector and the Multi-Purpose Module (Police And Taxi Interface Module-PTIM) 24 way harness connector (aftermarket light/siren controller side).

Is the resistance below 5.0 ohms?

Yes
1. Inspect the wiring and connectors for damage or shorted circuits. If ok, replace the Front Control Module in accordance with the service information.
2. Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1) .
No
1. Repair the (W527) Multi-Purpose Module (Police And Taxi Interface Module-PTIM) CAN B Bus (+) circuit for an open.
2. Perform BODY VERIFICATION TEST - VER 1. (Refer to BODY VERIFICATION TEST - VER 1) .