GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B3600 03 : Voltage Below Threshold

DTC B3600 07: Voltage Above Threshold

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

DIM Fuse B+

2

2

--

--

I/P Dimmer Voltage Reference

B1395 03 and B3600 03

B1395 03, B2652 00, and B3600 03

B1395 07

--

IS LPS Fuse B+

2

2

--

--

I/P DImmer Switch Signal

B1395 03

2

2

--

Stop Lamp Switch Signal

B1395 03 and B3600 03

3

3

--

I/P Dimming Control

B2625 00 and B2652 00

2

2

--

LED DImming Supply

B2610 00 and, B2625 00

B2610 00

B2610 00

--

Park Lamp Control

2

2

2

--

Indicator Dimming Low Reference

2

2

2

--

I/P Dimmer Switch Low Reference

--

1

--

--

I/P Dimmer Switch Ground

--

2

--

--

1. Dimmer Switch Malfunction

2. Interior Backlighting Malfunction

3. Stop Lamp Switch Malfunction

Circuit/System Description

The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level. Ground for the I/P dimmer switch is provided at G200.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B3600 03

The BCM detects a voltage that is lower than 0.10 volt on the I/P lamp dimmer switch signal circuit.

B3600 07

The BCM detects a voltage that is higher than 4.97 volts on the I/P lamp dimmer switch signal circuit.

Action Taken When the DTC Sets

The I/P lamps are not illuminated.

Conditions for Clearing the DTC

The BCM clears this code from current when the fault is removed from the system.

Reference Information

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the headlamp switch.
  2. Ignition OFF, verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
  3. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify the scan tool Dimming Control Signal parameter is less than 0.1 volts.
  5. If greater than the specified range, test the signal circuit terminal 13 for a short to voltage. If the circuit tests normal, replace the BCM.
  6. Ignition ON, test for B+ between the I/P dimming voltage reference circuit terminal 15 and ground.
  7. If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  8. Install a 3A fused jumper wire between the signal circuit terminal 13 and the voltage reference circuit terminal 15. Verify the scan tool BCM Dimming Control Signal parameter is greater than 2.6 volts.
  9. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  10. If all circuits test normal, test or replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Headlamp Switch Replacement
    •  Control Module References for BCM replacement, setup, and programming