Hummer H3. Manual — part 1407

Daytime Running Lamp Control Circuit High

Diagnostic Fault Information

DTC B2602 or B2603

Circuit/System Description

The daytime running lights (DRL) relay is controlled by the body control module (BCM). Battery
positive voltage is applied to the relay coil at all times. The BCM grounds the DRL relay control
circuit in order to turn ON the DRL relay illuminating the low beam headlamps at a reduced
intensity.

Conditions for Running the DTC

The ignition switch is in the RUN position.

The headlamp switch is in the AUTO position.

The park brake is not applied.

The gear selector is not in the PARK position.

Conditions for Setting the DTC

One of the following conditions must occur:

The DRL relay control circuit is open, shorted to ground or shorted to voltage.

The DRL relay coil is open.

The battery positive voltage to the DRL relay is open.

Action Taken When the DTC Sets

The BCM stores DTC B2602 or B2603 in memory.

The BCM disables the DRL relay control as long as the fault is present.

The BCM disables the DRL relay control until the next key cycle after the fault is corrected.

Conditions for Clearing the DTC

A current DTC B2602 or B2603 clears when the BCM no longer detects an open, short to
ground or short to battery positive voltage in the control circuit on the DRL relay.

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

DRL Control Circuit

B2602

B2602

B2603

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2007 ACCESSORIES & EQUIPMENT Lighting - H3

100 consecutive ignition cycles have been recorded without the DTC being detected.

Using a scan tool can clear the DTC.

Diagnostic Aids

The park brake must not be set and the transmission must be is gear for the DRL to operate
property.

An open, short to ground or a short to voltage in the following location may cause a
malfunction to occur:

The control circuit of the DRL relay coil

The DRL relay

The BCM

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Scan Tool Data Definitions

Scan Tool Data List

Scan Tool Output Controls

Circuit/System Verification

Ignition ON, carefully supply sufficient light to the ambient light sensor to activate DRL mode.
The BCM Output Data List should indicate that the DRL Status is On. The low beam headlamps
should illuminate at a reduced intensity.

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Circuit/System Testing

1. Ignition OFF, disconnect the DRL relay.

2. Ignition ON, verify that a test lamp illuminates between the relay coil voltage supply circuit

and ground.

If the test lamp does not illuminate, repair the voltage supply circuit for a short to
ground or an open/high resistance. If the voltage supply circuit fuse is open, test the
relay switch control circuit for a short to ground. If the circuit tests normal, test or
replace the DRL relay.

3. Disconnect the harness connector at the BCM.

4. Test for infinite resistance between the DRL relay control circuit and ground

If less than infinite, test the DRL relay control circuit for a short to ground.

5. Connect the harness connector at the BCM.

6. Connect a test lamp between the relay coil control circuit and the relay coil voltage supply

circuit.

7. Cycle the key OFF and then ON. Perform the Circuit/System Verification. The test lamp

should turn ON.

If the test lamp remains OFF all the time, test for a short to voltage or an open/high
resistance on the relay coil control circuit. If the circuit tests normal, replace the BCM.

If the test lamp remains ON all the time, test for a short to ground on the relay coil
control circuit. If the circuit tests normal, replace the BCM.

8. If all circuits test normal, test or replace the DRL relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the DRL relay.

2. Test for 65 to 95 ohms of resistance between terminals 85 and 86.

If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

30 and 86

30 and 87

30 and 85

85 and 87

If less than infinite resistance, replace the relay.

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2007 ACCESSORIES & EQUIPMENT Lighting - H3

4. Test for less than 2 ohms of resistance between terminals 30 and 87A.

If greater than 2 ohms, replace the relay.

5. Install a 10-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper

wire between relay terminal 86 and ground. Measure for less than 2 ohms of resistance
between terminals 30 and 87.

If greater than 2 ohms, replace the relay.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an
Electrical Center)

Control Module References for BCM replacement, setup and programming

DTC B2622 OR B2623

Circuit Description

The body control module (BCM) receives a variable voltage signal from the instrument panel
(I/P) dimmer switch requesting to illuminate the I/P controls illumination lamps to a desired
intensity. When this occurs, the BCM directly sends a variable voltage based on the I/P dimmer
switch position through the I/P lamps supply voltage circuit to the I/P controls illumination
lamps.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

DTC B2622 Dimming Display Pulse Width Modulation (PWM) Input Circuit Low

DTC B2623 Dimming Display Pulse Width Modulation (PWM) Input Circuit High

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

When the BCM receives an I/P controls illumination lamp request signal and the I/P lamps
supply voltage circuit is shorted to ground

When the BCM is not receiving an I/P controls illumination lamp request signal and the I/P

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Lighting - H3