GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1999 🢒 Cutlass 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B2603 DRL Relay Output Short to Battery

Circuit Description

This is a trouble code (both current and history) that indicates the DRL relay control output is shorted to battery.

Conditions for Setting the DTC

All of the following conditions must be met:

    • The ignition switch is in the RUN position.
    • The transaxle range switch is not in the PARK position.
    • The DRL option is configured.
    • The DRL relay output is active.
    • The DRL feedback is not present for 5 seconds.

Action Taken When the DTC Sets
    • Turns OFF the DRL relay
    • Enters a fault state
    • Stores DTC B2603 in the BCM memory
    • The SERVICE VEHICLE SOON indicator will illuminate.

Conditions for Clearing the DTC
    • The fault state is exited upon the program return to the DRL OFF state.
    • All the BCM history codes will be cleared after 100 ignition cycles (from OFF to RUN) with no current codes active during the 100 ignition cycles.
    • Use the scan tool.

Diagnostic Aids

If the DTC is a history DTC, the problem may be intermittent. Perform the above tests while wiggling the wiring and connectors. This may often cause the malfunction to appear.

Test Description

The numbers below refer to the numbers on the diagnostic table.

  1. This step determines if the DRL relay is operating properly.

    2.

  2. This step determines if there is a short to the battery in CKT 592 within the underhood wiring harness junction block.

    3.

  3. This step determines if there is a short to the battery in CKT 592 between the underhood wiring harness junction block and the body control module (BCM).

Step

Action

Value(s)

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.

1

Was the BCM System Check performed?

--

Go to Step 2

Go to Body Control Module System Check

2

  1. Replace the DRL relay with a known good relay on the underhood wiring harness junction block.
  2. Use the scan tool in order to enable the DRL relay.

Did the DRL relay activate?

--

Go to Step 8

Go to Step 3

3

  1. Remove the DRL relay on the underhood wiring harness junction block.
  2. Backprobe the underhood wiring harness junction block connector C3 terminal B12.
  3. Use the J 39200 Digital Multi Meter in order to measure the voltage in CKT 592 between the underhood wiring harness junction block connector C3 terminal B12 and ground.

Does the measured voltage equal the specified value?

0 V

Go to Step 5

Go to Step 4

4

Replace the underhood wiring harness junction block. Refer to Underhood Fuse Block Replacement in Engine Electrical.

Is the repair complete?

--

Go to Step 8

--

5

  1. Disconnect the BCM connector C1.
  2. Use the J 39200 DMM in order to measure the voltage in CKT 592 between the underhood wiring harness junction block harness connector C3 terminal B12 and ground.

Does the measured voltage equal the specified value?

0 V

Go to Step 6

Go to Step 7

6

Replace the BCM. Refer to the following procedures:

    •  Body Control Module Replacement in Instrument Panel, Gauges and Console

Is the repair complete?

--

Go to Step 8

--

7

Repair the short to B+ in CKT 592 between the BCM connector C1 terminal B5 and the underhood wiring harness junction block harness connector C3 terminal B12.

Is the repair complete?

--

Go to Step 8

--

8

Clear the DTCs from the memory.

Are the DTCs cleared from the memory?

--

Go to Body Control Module System Check

--