91 corvette abs light on
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91 corvette abs light on
Hello my brother has a 1991 corvette convertible. the abs light is on and when i jump the proper pins in DLC the abs light does not flash at all. Has anyone run across this issue before? Thank you for any help you can give.
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I can't say I've had this issue, but I took a look in the FSM Section 5E1 for you.
"About 3 seconds after ALDL terminal H is grounded the ECBM will begin flashing the SERVICE ABS indicator if Current Codes EXCLUDING 41, 45, 55, 61 and 63 are set." (Emphasis mine.)
These codes are the (3) Wheel solenoid valves fault (41, 45, 55), Pump motor relay fault (61), and Solenoid valve relay fault (63). My interpretation of your "no flash" is that one of these (5) codes is set. The manual says that these codes can only be retrieved with a Tech-1.
EDIT/ADD: I've been studying the FSM. These codes are all associated with no power to the ABS, or a wheel solenoid fault that disables the Solenoid Valve Relay. When the solenoid valve relay is not energized (It normally is energized any time the key is in RUN) the SERVICE ABS light is grounded by the N.C. contacts in the valve relay. If the relay is not energized, the light can not flash because it is independently grounded.
Without a Tech-1, here's what I would try: In the compartment behind the driver seat try to locate the "ABS Diode Module". It probably looks like a wad of friction tape with two tan and two white wires going to it. Disconnect either both tan or both white wires. This disables the "always on", "independently grounded" ABS light. Turn the key to RUN. If the ABS light comes on for bulb test, then goes off, the unit powered up. Now jumper A and H and the codes should be visible. If the ABS light does not bulb test, there is probably a power supply problem. There is a fuse link at the battery, and BRAKE and AIR BAG fuses supply the ABS module.
If you have the FSM, a VOM; some understanding of automotive electrical and can decipher schematics, I feel that the 90-91 ABS can be diagnosed without a Tech-1. Go for it.
Last edited by IHBD; Jul 6, 2025 at 03:23 AM.
Thread Starter
Advanced
Joined: Oct 2013
Posts: 66
Likes: 1
I assUme that the "proper pins" are cavity A and H?
I can't say I've had this issue, but I took a look in the FSM Section 5E1 for you.
"About 3 seconds after ALDL terminal H is grounded the ECBM will begin flashing the SERVICE ABS indicator if Current Codes EXCLUDING 41, 45, 55, 61 and 63 are set." (Emphasis mine.)
These codes are the (3) Wheel solenoid valves fault (41, 45, 55), Pump motor relay fault (61), and Solenoid valve relay fault (63). My interpretation of your "no flash" is that one of these (5) codes is set. The manual says that these codes can only be retrieved with a Tech-1.
EDIT/ADD: I've been studying the FSM. These codes are all associated with no power to the ABS, or a wheel solenoid fault that disables the Solenoid Valve Relay. When the solenoid valve relay is not energized (It normally is energized any time the key is in RUN) the SERVICE ABS light is grounded by the N.C. contacts in the valve relay. If the relay is not energized, the light can not flash because it is independently grounded.
Without a Tech-1, here's what I would try: In the compartment behind the driver seat try to locate the "ABS Diode Module". It probably looks like a wad of friction tape with two tan and two white wires going to it. Disconnect either both tan or both white wires. This disables the "always on", "independently grounded" ABS light. Turn the key to RUN. If the ABS light comes on for bulb test, then goes off, the unit powered up. Now jumper A and H and the codes should be visible. If the ABS light does not bulb test, there is probably a power supply problem. There is a fuse link at the battery, and BRAKE and AIR BAG fuses supply the ABS module.
If you have the FSM, a VOM; some understanding of automotive electrical and can decipher schematics, I feel that the 90-91 ABS can be diagnosed without a Tech-1. Go for it.
I can't say I've had this issue, but I took a look in the FSM Section 5E1 for you.
"About 3 seconds after ALDL terminal H is grounded the ECBM will begin flashing the SERVICE ABS indicator if Current Codes EXCLUDING 41, 45, 55, 61 and 63 are set." (Emphasis mine.)
These codes are the (3) Wheel solenoid valves fault (41, 45, 55), Pump motor relay fault (61), and Solenoid valve relay fault (63). My interpretation of your "no flash" is that one of these (5) codes is set. The manual says that these codes can only be retrieved with a Tech-1.
EDIT/ADD: I've been studying the FSM. These codes are all associated with no power to the ABS, or a wheel solenoid fault that disables the Solenoid Valve Relay. When the solenoid valve relay is not energized (It normally is energized any time the key is in RUN) the SERVICE ABS light is grounded by the N.C. contacts in the valve relay. If the relay is not energized, the light can not flash because it is independently grounded.
Without a Tech-1, here's what I would try: In the compartment behind the driver seat try to locate the "ABS Diode Module". It probably looks like a wad of friction tape with two tan and two white wires going to it. Disconnect either both tan or both white wires. This disables the "always on", "independently grounded" ABS light. Turn the key to RUN. If the ABS light comes on for bulb test, then goes off, the unit powered up. Now jumper A and H and the codes should be visible. If the ABS light does not bulb test, there is probably a power supply problem. There is a fuse link at the battery, and BRAKE and AIR BAG fuses supply the ABS module.
If you have the FSM, a VOM; some understanding of automotive electrical and can decipher schematics, I feel that the 90-91 ABS can be diagnosed without a Tech-1. Go for it.
