GM Service Manual Online
For 1990-2009 cars only

Object Number: 331255  Size: MF
Body Control Module Components
Cell 100: Headlamp Switch and Headlamp Control
Body Control System Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

When the exterior lamps are commanded ON, the body control module (PZM) energizes the headlamp relay and the parklamp relay through PZM connector C2 terminals C9 and C6, respectively. Power for these relays is also provided by the PZM through connector C2 terminal C16. Every 300 ms, the PZM determines the voltage at these terminals and compares it to the commanded state.

Conditions for Setting the DTC

The exterior lamps are commanded on for at least 300 ms and the exterior lamp power is low for at least 2 consecutive monitoring cycles.

Action Taken When the DTC Sets

The PZM commands the exterior lamps OFF and attempt to turn the lamps ON every 1200 ms until the exterior lamps are no longer required.

Conditions for Clearing the DTC

The exterior lamps are commanded ON and the exterior lamp power is active after 2 consecutive monitoring cycles.

    • When the measurements are requested in the table below, use the J 39200 Digital Multimeter (DMM) with the correct terminal adapter from J 35616 .
    •  When a proper connection is requested, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
    • When a wire, connector or terminal repair is requested, use J-38125 . Refer to Wiring Repairs in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This test inspects the surface-mounted fuse in the PZM for opens due to a short to ground on CKT 352 (WHT).

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition to the OFF position.
  2. Disconnect the parklamps relay.
  3. Disconnect the headlamps relay.
  4. Disconnect the body control module.
  5. Measure the resistance from the parklamps relay connector terminal A6 to ground.

Is the resistance less than or equal to the specified value?

5 ohms

Go to Step 3

Go to Step 2

2

Replace the body control module. Refer to Body Control Module Replacement in Body Control System.

Is the body control module replacement complete?

--

Go to Diagnostic System Check - Lighting Systems

--

3

  1. Repair the short to ground in CKT 352 (WHT). Refer to Wiring Repairs in Wiring Systems.
  2. Reconnect all of the components.
  3. Turn the ignition to the ON position.
  4. Turn the headlamps to the ON position.

Do the headlamps turn ON?

--

Go to Diagnostic System Check - Lighting Systems

Go to Step 2