Brake light problem
Thread Starter
Le Mans Master
Joined: Jul 1999
Posts: 5,005
Likes: 38
From: jackson nj
Brake light problem
I have what seems to be a strange issue with my 2003 and I'd like any input on finding what it is, and it's fix. The R/H brake and directional will sometimes not work and then without any repair, it starts to work again and will stay working for a different amount of time during each episode. 
I have checked the bulbs and sockets, disconnected the body harness plug and checked the terminal ends (which all seem good) and nothing has come to light as to what the issue is caused by. Has anybody had this happen to them on their Corvette or any type car? If so, what fixed the problem? 
I have checked the bulbs and sockets, disconnected the body harness plug and checked the terminal ends (which all seem good) and nothing has come to light as to what the issue is caused by. Has anybody had this happen to them on their Corvette or any type car? If so, what fixed the problem?
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Intermittent electrical issues are difficult to troubleshoot if the system only works intermittently. Yours working most times makes it a bit easier.
The bulb may have a broken contact inside the glass portion but not be "open" at all times. Holding the bulb in your finger-tips by the contact points and tapping/flicking the glass portion with your other hand; may show the filament waving/vibrating in the glass. No movement indicates a good bulb, movement or waving indicates a fractured filament and will only work when touching itself and any movement will cause a loss of contact and hence no light. I would change the bulb regardless given the cost.
If the bulb looks good then i would search for a bad contact or compromised wiring. It's always easier to have two people; if not a large mirror; to monitor the light, will suffice. Use a rod or stick to press and hold/lock the brake peddle. Have someone keep an eye on the brake light as you move and follow the wiring from the bulb/socket area back to the signal switch. With luck when you hit the loose or broken point the light will extinguish and you can identify the problem. Check not only the ground points but the connection of the wiring to the terminal itself as corrosion may be the issue at the wire/terminal.
The fact that your issue affects both brake and signal indication leads me towards the bulb or wiring as the most likely cause.
Dan
The bulb may have a broken contact inside the glass portion but not be "open" at all times. Holding the bulb in your finger-tips by the contact points and tapping/flicking the glass portion with your other hand; may show the filament waving/vibrating in the glass. No movement indicates a good bulb, movement or waving indicates a fractured filament and will only work when touching itself and any movement will cause a loss of contact and hence no light. I would change the bulb regardless given the cost.
If the bulb looks good then i would search for a bad contact or compromised wiring. It's always easier to have two people; if not a large mirror; to monitor the light, will suffice. Use a rod or stick to press and hold/lock the brake peddle. Have someone keep an eye on the brake light as you move and follow the wiring from the bulb/socket area back to the signal switch. With luck when you hit the loose or broken point the light will extinguish and you can identify the problem. Check not only the ground points but the connection of the wiring to the terminal itself as corrosion may be the issue at the wire/terminal.
The fact that your issue affects both brake and signal indication leads me towards the bulb or wiring as the most likely cause.
Dan
Melting Slicks
Joined: Nov 1999
Posts: 2,347
Likes: 857
From: MI
Cruise-In VI Veteran
Systems Description and Operation
Turn Signal Lamps
Ignition positive voltage from the HAZT/SIG fuse 15 in the instrument panel fuse block is supplied to the hazard warning switch. The turn signal lamps may only be activated with the ignition switch in the ON or ACCY position. When the turn signal switch is placed in either the left or right position, the flasher module sends an ON/OFF voltage to the turn signal switch assembly. For the rear turn lamps, battery voltage is applied directly to either the left or right turn signal lamps. The ground for the rear turn lamps is supplied from G401. For the front turn lamps, battery positive voltage is applied from the turn signal switch to the instrument panel electrical center. From the instrument panel fuse block, battery positive voltage is applied to the instrument cluster (IC) indicators and to the normally-open switched side of either the DRL L or DRL R relay, depending on the turn signal switch position. Battery positive voltage is then applied to either the left or right turn signal lamps. The front turn signals are grounded at G102.
For the hazard lamps, voltage is applied from the STP HAZ fuse 8 to the hazard warning switch. When the hazard switch is pressed, all the turn signal lamps will flash, including both IPC turn signal indicators. The hazard warning switch is grounded at G201.
Turn Signal Reminder
The IPC activates theturn signal warning as requested by the IPC. The IPC receives a low input signal from the turn signal switch indicating the chime frequency (medium rate) and duration (continuos). The turn signal warning sounds when the following occurs:
• The ignition is in RUN.
• The turn signal switch is in either turn position, sensing, within 1 second, an open to B+ transition in the turn signal control circuit (left or right turn).
• The vehicle has traveled a distance of 1.2 km (0.75 mi) by counting pulses on the vehicle speed input circuit.
The IPC turns off the turn signal reminder when either the ignition switch is turned to the OFF position, or the turn signal switch returns to the OFF position, or the turn signal switch returns to the OFF position, sensing, within 1 second, no transitions from open to B+ in either of the turn signal control circuits (left turn or right turn).
Stop lamps
The STP HAZ fuse in the instrument panel fuse block supplies battery positive voltage to the normally-open stop lamp switch.
Domestic
When the driver presses the brake pedal, the switch contacts close and the stop lamp output signal is applied to the CHMSL and to the hazard warning switch. The stop lamp signal is applied from the hazard warning switch to the turn signal switch. The turn signal switch applies the stop lamp switch signal to both of the rear stop/turn lamps, turning them on full bright. The stop/turn lamps ground is applied from G401.
Step
Action
Yes
No
Schematic Reference: Exterior Lights Schematics
Connector End View Reference: Master Electrical Component List
1
Did you perform the Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Lighting Systems
2
Turn the ignition to the RUN position.
Turn the turn signal switch to the TURN LEFT position and then to the TURN RIGHT position.
Do the turn signal lamps and the turn signal indicators flash?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Are only the turn signal indicators inoperative?
Go to Step 5
Go to Step 4
4
Are all of the turn lamps inoperative?
Go to Step 6
Go to Step 13
5
Leave the turn signal switch at the inoperative side.
Using a test lamp, backprobe the control circuit of the turn signal lamp indicator at the instrument panel cluster.
Does the test lamp flash?
Go to Step 8
Go to Step 11
6
Disconnect connector C215.
Using a test lamp connected to ground, probe the HAZT/SG fuse #15 battery positive voltage circuit.
Turn the ignition switch to the RUN position.
Does the test lamp illuminate?
Go to Step 7
Go to Step 12
7
Using a test lamp, probe between the HAZT/SG fuse #15 battery positive voltage circuit and the turn signal switch battery positive voltage supply circuit.
Turn the ignition to the RUN position.
Does the test lamp illuminate?
Go to Step 9
Go to Step 10
8
Inspect the harness connector of the instrument panel cluster for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 14
9
Inspect the harness connector of the hazard warning switch for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 15
10
Inspect the harness connector of the turn signal switch for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 16
11
Repair the open or the high resistance in the inoperative turn signal lamp indicator power supply circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
12
Repair the open, high resistance, or short to ground in the HAZT/SG fuse #15 battery positive voltage feed circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
13
Repair the open or the high resistance in the inoperative turn signal lamp power supply or ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
14
Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.
Did you complete the replacement?
Go to Step 17
--
15
Replace the hazard warning switch. Refer to Hazard Warning Switch Replacement .
Did you complete the replacement?
Go to Step 17
--
16
Replace the turn signal switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.
Did you complete the replacement?
Go to Step 17
--
17
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3
Turn Signal Lamps
Ignition positive voltage from the HAZT/SIG fuse 15 in the instrument panel fuse block is supplied to the hazard warning switch. The turn signal lamps may only be activated with the ignition switch in the ON or ACCY position. When the turn signal switch is placed in either the left or right position, the flasher module sends an ON/OFF voltage to the turn signal switch assembly. For the rear turn lamps, battery voltage is applied directly to either the left or right turn signal lamps. The ground for the rear turn lamps is supplied from G401. For the front turn lamps, battery positive voltage is applied from the turn signal switch to the instrument panel electrical center. From the instrument panel fuse block, battery positive voltage is applied to the instrument cluster (IC) indicators and to the normally-open switched side of either the DRL L or DRL R relay, depending on the turn signal switch position. Battery positive voltage is then applied to either the left or right turn signal lamps. The front turn signals are grounded at G102.
For the hazard lamps, voltage is applied from the STP HAZ fuse 8 to the hazard warning switch. When the hazard switch is pressed, all the turn signal lamps will flash, including both IPC turn signal indicators. The hazard warning switch is grounded at G201.
Turn Signal Reminder
The IPC activates theturn signal warning as requested by the IPC. The IPC receives a low input signal from the turn signal switch indicating the chime frequency (medium rate) and duration (continuos). The turn signal warning sounds when the following occurs:
• The ignition is in RUN.
• The turn signal switch is in either turn position, sensing, within 1 second, an open to B+ transition in the turn signal control circuit (left or right turn).
• The vehicle has traveled a distance of 1.2 km (0.75 mi) by counting pulses on the vehicle speed input circuit.
The IPC turns off the turn signal reminder when either the ignition switch is turned to the OFF position, or the turn signal switch returns to the OFF position, or the turn signal switch returns to the OFF position, sensing, within 1 second, no transitions from open to B+ in either of the turn signal control circuits (left turn or right turn).
Stop lamps
The STP HAZ fuse in the instrument panel fuse block supplies battery positive voltage to the normally-open stop lamp switch.
Domestic
When the driver presses the brake pedal, the switch contacts close and the stop lamp output signal is applied to the CHMSL and to the hazard warning switch. The stop lamp signal is applied from the hazard warning switch to the turn signal switch. The turn signal switch applies the stop lamp switch signal to both of the rear stop/turn lamps, turning them on full bright. The stop/turn lamps ground is applied from G401.
Step
Action
Yes
No
Schematic Reference: Exterior Lights Schematics
Connector End View Reference: Master Electrical Component List
1
Did you perform the Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Lighting Systems
2
Turn the ignition to the RUN position.
Turn the turn signal switch to the TURN LEFT position and then to the TURN RIGHT position.
Do the turn signal lamps and the turn signal indicators flash?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Are only the turn signal indicators inoperative?
Go to Step 5
Go to Step 4
4
Are all of the turn lamps inoperative?
Go to Step 6
Go to Step 13
5
Leave the turn signal switch at the inoperative side.
Using a test lamp, backprobe the control circuit of the turn signal lamp indicator at the instrument panel cluster.
Does the test lamp flash?
Go to Step 8
Go to Step 11
6
Disconnect connector C215.
Using a test lamp connected to ground, probe the HAZT/SG fuse #15 battery positive voltage circuit.
Turn the ignition switch to the RUN position.
Does the test lamp illuminate?
Go to Step 7
Go to Step 12
7
Using a test lamp, probe between the HAZT/SG fuse #15 battery positive voltage circuit and the turn signal switch battery positive voltage supply circuit.
Turn the ignition to the RUN position.
Does the test lamp illuminate?
Go to Step 9
Go to Step 10
8
Inspect the harness connector of the instrument panel cluster for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 14
9
Inspect the harness connector of the hazard warning switch for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 15
10
Inspect the harness connector of the turn signal switch for a poor connection. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 17
Go to Step 16
11
Repair the open or the high resistance in the inoperative turn signal lamp indicator power supply circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
12
Repair the open, high resistance, or short to ground in the HAZT/SG fuse #15 battery positive voltage feed circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
13
Repair the open or the high resistance in the inoperative turn signal lamp power supply or ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 17
--
14
Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.
Did you complete the replacement?
Go to Step 17
--
15
Replace the hazard warning switch. Refer to Hazard Warning Switch Replacement .
Did you complete the replacement?
Go to Step 17
--
16
Replace the turn signal switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.
Did you complete the replacement?
Go to Step 17
--
17
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Another issue that can be caused by a faulty brake light circuit is that if your car is an A4--anytime the brake switch is activated it will UNLOCK your TQ converter OR will NOT allow it to lock at all---
