DTC 21/31 Courtesy Lamps Feed Shorted to Ground. Pontiac Firebird 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 Body and Accessories 🢒 Lighting Systems 🢒 DTC 21/31 Courtesy Lamps Feed Shorted to Ground

Body Control Module Components
Body Control Module and Courtesy Lamps
Handling ESD Sensitive Parts Notice
COURTESY and RADIO ACCY Fuses

Circuit Description

The body control module (BCM) provides a 12 volt output to the courtesy lamps on circuit 149 through S241 when the BCM is in the awake state. Ground is applied to the courtesy lamps by the BCM though circuit 156 when commanded by one of the following components:

•	The instrument panel (IP) dimmer switch

•	The left side door lock

•	The right side door lock

•	The rear compartment lid ajar indication switch

S241 distributes power to the following lamps on the coupe model:

•	The dome lamp

•	The courtesy/reading lamp

S241 distributes power to the following lamps on the convertible model:

•	S317 (the left rear courtesy lamp and the rear compartment lamp)

•	The right rear courtesy lamp

•	The IP compartment lamp

•	The courtesy/reading lamps

Conditions for Setting the DTC

•	Circuit 40/1002 is open due to defective Courtesy Fuse 8.

•	There is a harness or connector failure.

•	Circuit 149 (courtesy lamps feed) is shorted to the ground for greater than 50 milliseconds while the BCM is attempting to power the circuit.

•	The BCM is defective.

Action Taken When the DTC Sets

•	DTC 21 will set.

•	There is no courtesy lighting in the vehicle.

•	The IP dimmer switch is inoperative.

•	The IP compartment lamp is inoperative.

•	The BCM will read out a series of flash DTCs upon entering diagnostic mode.

Conditions for Clearing the DTC

The fault is corrected and the DTC memory is cleared.

Diagnostic Aids

If the only DTC that flashes is a history code (DTC 31), the problem may be intermittent. Try performing the test shown while wiggling the wiring and the connectors. This action can often cause the fault to appear. Test for poor connections at the BCM connector. Poor connections may cause an open or an intermittent fault. Refer to Diagnostic Trouble Code (DTC) Displaying Displaying DTCs

Test Description

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

This step tests for an open COURTESY Fuse 8.

If COURTESY Fuse 8 is open, this step tests for a short to the ground on circuit 40.

If COURTESY Fuse 8 is OK, this step tests for an open in circuit 40 and circuit 1002.

This step tests for a short to the ground in circuit 149.

Step	Action	Value(s)	Yes	No
Important: Inspect for the proper installation of aftermarket electronic equipment which may affect the integrity of the system.
1	Did you perform the Diagnostic System Check?	--	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Check COURTESY Fuse 8 for an open. Is Fuse 8 open?	--	Go to Step 3	Go to Step 4
3	Test and repair circuit 40 for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. If OK, replace Fuse 8. Is the repair complete?	--	System OK	--
4	Disconnect the body control module (BCM) connector C2. Connect a test lamp between BCM connector C2 terminal B and ground. Refer to Circuit Testing in Wiring Systems. Does the test lamp illuminate?	--	Go to Step 6	Go to Step 5
5	Repair the open in circuit 40 or circuit 1002. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?	--	System OK	--
	Close the instrument panel compartment. Connect a DMM between BCM connector C2 terminal E and ground. B and ground. Refer to Circuit Testing in Wiring Systems. Does the meter read the specified value?	0 ohms	Go to Step 6	Go to Step 7
6	Repair the short to ground in circuit 149. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?	--	System OK	--
7	Important: Perform the set up procedure for the body control module (BCM). Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair.	--	System OK	--