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Re: Backup lights stopped working, replaced one complete...
I would say that the backup light switch on the transmission is faulty, or the wiring to and from the switch. Most times if the backup lights do not work this is the root cause.
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If you have a tow hitch and an electrical connection for a trailer, there is a problem with the wiring in the connector. Take it to a garage and they can fix for a small fee.
DTC B2550
When the body control module (BCM) receives a signal requesting to illuminate the backup lamps, battery voltage is sent directly from the BCM through the backup lamp supply voltage circuit to the backup lamps.
Voltage for the backup lamp supply voltage circuit as well as the courtesy lamp supply voltage circuit is from the left instrument panel fuse block TBC 2B 15-amp fuse directly through the BCM to these circuits.
Brake lights or do you mean tail lights ?
Stop Lamps Always On
Did you perform the Diagnostic System Check - Vehicle?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Vehicle
2
Depress the brake pedal.
Does the system operate normally?
YES - Go to Testing for Electrical Intermittents
No - Go to Step 3
3
Disconnect the stop lamp switch.
Do the brake lamps go out?
YES - Go to Step 6
No - Go to Step 4
4
Remove the CHMSL fuse.
Do the brake lamps go out?
Yes - Go to Step 7
NO - Go to Step 5
5
Remove the STOP fuse.
Do the brake lamps go out?
YES - Go to Step 8
NO - Go to Step 9
6
Inspect for poor connections at the harness connector of the switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.
Did you find and correct the condition?
YES - Go to Step 11
NO - Go to Step 10
7
Repair the short to voltage in the CHMSL supply voltage circuit. Refer to Wiring Repairs.
Did you complete the repair?
YES - Go to Step 11
--
8
Repair the short to voltage in the stop lamp switch signal circuit. Refer to Wiring Repairs.
Did you complete the repair?
Go to Step 11
--
9
Repair the short to voltage in the stop lamp supply voltage circuit. Refer to Wiring Repairs.
Did you complete the repair?
Go to Step 11
--
10
Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement.
Did you complete the replacement?
Go to Step 11
--
11
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3
Replace the backup light on the right side. Its most likely burned out. A blown fuse would cause both lights to not work. You might have bad wiring to that side. If you have access to a volt meter, have an assistant put your car in reverse while you check the voltage at the backup light socket. Make sure to tell your assistant to keep their foot on the brake pedal. Voltage should about 12 volts
Lighting control module ? ?????? Hazard / flasher module ! Now ( there''s not even an electrical signal where the fuse plugs into the interior fuse panel.) What FUSE ??????
Stop Lamps
The STOP LP 25 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the STOP 15 A fuse and the CHMSL 10 A fuse in the I/P fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits. The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.
Backup Lamps
The backup lamp request signal is sent from the powertrain control module (PCM) to the body control module (BCM) on the Class 2 message system. This signal is based on the park neutral position (PNP) switch signal. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. Voltage for the courtesy lamp supply voltage circuit and backup lamp supply voltage circuit is from the TBC B fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to ground on either of these circuits will open the fuse. The backup lamps are grounded at G401.
For trailer wiring, a separate backup lamp circuit is connected through the underhood fuse block from the TRLR B/U 10 A fuse to the trailer wiring harness.
Turn Signal/Hazard Lamps
The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal/hazard switch assembly. The FLASH 25 A fuse in the I/P fuse block supplies battery positive voltage to the turn signal/flasher module and ground is supplied at G200. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn sign/flasher module. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the turn sign/flasher module. The turn sign/flasher module then sends an on-off voltage signal through the LT TRLR, RT TRLR, LT TURN or RT TURN 10 A fuses in the I/P fuse block to the appropriate turn signal or to all 4 fuses for hazard operation. The instrument panel cluster (IPC) indicators receive voltage from the LT TURN and RT TURN fuses as well as the DDM/PDM for the mirror turn signals. The DDM/PDM has no function or control of the mirror turn signals other that a pass through connection for the circuits. The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100. The rear turn signals are grounded at G401. The Mirror turn signals are grounded by the DDM/PDM.
Do you know how to do automotive electrical circuit testing with a test light or volt meter ? How to read an use a wiring diagram to pin point testing points . ( connectors , fuse locations etc... ) How to use a power flow chart ? Here is a site for just such info .
Stop Lamp Circuit Description
The STOP HAZ fuse in the IP junction block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to the center mounted stop lamp (CHMSL) and both left and right stop lamp assemblies. The left stop lamp is grounded at G304 and the right stop lamp is grounded at G304.
2
Inspect the 20 Amp STOP HAZ fuse.
Is the STOP HAZ fuse open?
YES - Go to Step 11
NO - Go to Step 3
3
Use a test lamp in order to backprobe connector C1 of the brake switch connector between terminal A and ground. Refer to Circuit Testing in Wiring Systems.
Does the test lamp light?
YES - Go to Step 4
NO - Go to Step 5
4
With the brake switch closed, Test for positive battery voltage at terminal B of connector C1. Refer to Circuit Testing in Wiring Systems.
Is voltage present?
YES - Go to Step 6
NO - Go to Step 7
5
Repair the open or short to ground in the Fuse Output-Battery between the fuse block and the brake switch. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
YES - System OK
--
6
Use a test lamp in order to backprobe the turn/hazard headlamp switch assembly connector C2 terminal A and ground.
Depress the brake pedal.
Does the test lamp light?
YES - Go to Step 8
NO - Go to Step 9
7
Inspect the adjustment of the brake switch. If the adjustment is correct, replace the brake switch.
Is the repair complete?
YES - System OK
--
8
Replace the turn/hazard headlamp switch assembly.
Is the repair complete?
System OK
--
9
Repair the open in Stop Lamp Switch Output between the brake switch and the turn/hazard headlamp switch assembly. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
System OK
--
10
With brake switch open test terminal A of the brake switch for continuity to ground. Refer to Circuit Testing in Wiring Systems.
Is ground present?
YES - Go to Step 11
NO - Go to Step 12
11
Repair short to ground in Fuse Output-Battery Circuit. Refer to Wiring Repairs in Wiring Systems.
Is repair complete?
System OK
--
12
Test the Stop Lamp Switch Output Circuit for continuity to ground. Refer to Circuit Testing in Wiring Systems.
Is ground present?
YES - Go to Step 13
NO - Go to Step 14
13
Repair short to ground in the Stop Lamp Switch Output Circuit. Refer to Wiring Repairs in Wiring Systems.
Is repair complete?
System OK
--
14
Test terminals F,G,B and C on the Hazard Warning Switch for continuity to ground. Refer to Circuit Testing in Wiring Systems.
Is ground present?
Go to Step 15
--
15
Repair short to ground in suspect CKT. Refer to Wiring Repairs in Wiring Systems.
Is repair complete?
System OK
--
if the two lights your talking about are in the 3rd brk light assembly, those are not reverse lights they are cargo compartment lights ...... the reverse lights are in the brake light assemblies- if they dont work replace the rev light sw on the tranny
Did you check to see whether or not the bulbs need replaced? Although it would be weird to have all the rear lights blow at once unless it shorted out somehow. I would also check under the hood for a blown fuse in the relay box.
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