91 Corvette courtesy light problems
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
91 Corvette courtesy light problems
91 roadster's interior lights stay on all the time and can not be shut off sans disconnecting the lights or the battery.
I believe that the courtesy light delay module for a 1991 L98 is controlled by the CCM, Can anyone verify this or help with the location of the interior and courtesy lights controller or relay?
I believe that the courtesy light delay module for a 1991 L98 is controlled by the CCM, Can anyone verify this or help with the location of the interior and courtesy lights controller or relay?
Instructor
Joined: Jun 2008
Posts: 173
Likes: 0
From: Norman OK
You are correct. According to my 91 FSM, the courtesy lamp relay is energized by the CCM whenever the l/h or r/h door is open. The courtesy lamp relay is located below the r/h side of the i/p in a 2 relay bracket. The other relay will be for the fog lights.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
You are correct. According to my 91 FSM, the courtesy lamp relay is energized by the CCM whenever the l/h or r/h door is open. The courtesy lamp relay is located below the r/h side of the i/p in a 2 relay bracket. The other relay will be for the fog lights.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
Thread Starter
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
You are correct. According to my 91 FSM, the courtesy lamp relay is energized by the CCM whenever the l/h or r/h door is open. The courtesy lamp relay is located below the r/h side of the i/p in a 2 relay bracket. The other relay will be for the fog lights.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
FSM indicates the following :
A defective door key switch may keep Courtesy Lamps on. Also, check CCM for Code 25 -if found, t/s CCM faults.
Disconnect Light Switch Connector C1 - Lights off? Yes, bad switch.
Remove Courtesy Light Relay - Lights off? Yes, bad relay or wiring problems.
Instructor
Joined: Jun 2008
Posts: 173
Likes: 0
From: Norman OK
Here are the wiring checks if you need them from t/s Chart 3...
Remove Courtesy Lamp Relay - Lights Off?
No - Repair short to ground in CKT 156. (White wires from individual lamps to relay Term 1)
Yes - LH Door Closed, Connect test light between Term C12 of the CCM Module Grey Connector and B+.
Is test light on?
Yes - Check for short to ground in CKT 745. (Blk/Yel wire from CCM C12 to l/h door ajar switch). If ok, replace left door ajar switch.
No - Connect the test light between Term D16 of the same connector and B+. RH door closed.
Is test light on?
Yes - Check for short to ground in CKT 746. (Blk/Wht wire from CCM D16 to r/h door ajar switch). If ok, replace right door ajar switch.
No - Check for the presence of ground at Courtesy Lamp Relay Term 2. If present, check for short to ground in CKT 690. (Gry/Blk wire between relay term 2 and D12 of CCM grey connector). If not shorted to ground, replace CCM. If ground was not present, replace the Courtesy Lamp Relay.
Good luck..
Remove Courtesy Lamp Relay - Lights Off?
No - Repair short to ground in CKT 156. (White wires from individual lamps to relay Term 1)
Yes - LH Door Closed, Connect test light between Term C12 of the CCM Module Grey Connector and B+.
Is test light on?
Yes - Check for short to ground in CKT 745. (Blk/Yel wire from CCM C12 to l/h door ajar switch). If ok, replace left door ajar switch.
No - Connect the test light between Term D16 of the same connector and B+. RH door closed.
Is test light on?
Yes - Check for short to ground in CKT 746. (Blk/Wht wire from CCM D16 to r/h door ajar switch). If ok, replace right door ajar switch.
No - Check for the presence of ground at Courtesy Lamp Relay Term 2. If present, check for short to ground in CKT 690. (Gry/Blk wire between relay term 2 and D12 of CCM grey connector). If not shorted to ground, replace CCM. If ground was not present, replace the Courtesy Lamp Relay.
Good luck..
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
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Heel & Toe
Joined: Aug 2010
Posts: 24
Likes: 0
Check your door lock cylinders. If the key is removed with the lock not in the upright position, the lights will stay on. My '93 had the same problem. Put the key in the door locks and repositioned the cylinder and the lights went out.
Heel & Toe
Joined: Dec 2010
Posts: 17
Likes: 0
On a related vein...I just bought a '93 and have been troubleshooting a H/C25 code on my CCM (SYS flashing)...I removed a sick sounding buzzer when I first bought the car because it was driving me nuts. I found it just under the glove box. As I started driving it more in the dark I realized that my courtsey lights dont come on when I open either door. My first target was the fuse block and just today I located / replaced a blown LH courtesy 5A fuse. The courtesy lights still wont come on (only when I pop the hatch). All other CCM and Courtesy fuses are good.
Instructor
Joined: Jun 2008
Posts: 173
Likes: 0
From: Norman OK
If your 93's courtesy lights are wired the same as my 91, the 91 FSM states CCM Code 25 fault is: Courtesy Lamp Relay Coil Circuit Open or Shorted to Ground. The relay may have failed and took out the fuse with it. I would check the relay.
