How to Manually Read EBCM ABS Codes on a 1992 Oldsmobile Delta 88 with ALDL Connector

I'll check my information system. I believe ground terminal A (top right) should be connected to terminal H (second from left on bottom row). Turn the ignition to 'ON' without cranking and count the ABS light flashes—this is how you retrieve EBCM error codes.

I believe it's terminal H. Jumper terminal A (ground, top right) to terminal H (second from left on bottom row). Turn ignition to 'ON' without cranking and observe the ABS light flashes—likely two flashes with a pause, possibly followed by code 12. This is a known flash pattern for Teves Mark IV systems. I'll verify this later.

I agree with terminal H. My service manual lists the EBCM error codes. I’ll try this tomorrow during daylight hours. The ABS light has been on for a while, and I’ve already checked all wheel sensors. Getting an actual code would make troubleshooting much easier. Thanks for sharing—many local parts stores don’t carry OBD1 readers for pre-1996 vehicles.

Let me know how the flash diagnostic works and what code you get—I can cross-reference it in my database.

I just checked—there is no wire connected to terminal H on the connector. The rest of the bottom row has wires, but not H. This may mean the flash diagnostic method isn't applicable or requires a different approach.

Let me look up the 12-pin ABS connector wiring diagram in my system to confirm terminal locations and connections.

I'm sorry—I don’t have access to that information anymore. I once had GM ABS and OBD1 reference books, but I threw them away years ago. AutoZone likely doesn't support OBD1 code reading for pre-1996 vehicles. Older tools like the Snap-on MT2500 (red brick model) might still be available on eBay—worth checking. Best of luck with your diagnosis.

I found fuses 6, 13, and 19 under the dash, and fuses 1 and 2 in the underhood fuse block—all related to ABS. What kind of braking issue are you experiencing? Any pulsation or loss of brake feel?

The ABS light is on continuously. The system used to work intermittently—sometimes ABS engaged, sometimes not—but now it's solidly lit. This led me to suspect a wiring fault. I’ve already checked all wheel sensors and found no issues. I’m now leaning toward an electrical or relay problem. Thanks for the help—I’ll keep troubleshooting manually.

After some research, this is a Teves Mark IV ABS system—EBCM codes require a dedicated scan tool to access. I recommend checking fuses (6, 13, 19 under dash; 1 and 2 under hood). Try disconnecting the negative battery terminal for 10 seconds, then turn ignition to 'ON' without cranking. If the ABS light stays on briefly and turns off, it may reset successfully. Also: does both the ABS and traction control lights stay on? If not, perform a test drive—pay attention at low speeds (under 25 mph) when applying brakes. Note any pedal pulsation or brake feel changes. Please share your results.

All fuses are good—verified visually and with an ohmmeter. After disconnecting the battery for 10 seconds, I reconnected and turned the key to 'ON'. The ABS light stayed on briefly before turning off. This car doesn’t have traction control. There are seven relays under the hood—two are labeled as ABS (Main and Pump). I’m reviewing the service manual to identify them. Brakes function normally but lack ABS, with a slightly different pedal feel. As someone who didn’t grow up with anti-lock brakes, it’s not a major concern—but I wanted to resolve this so the warning light doesn’t persist.

After starting the car, the ABS light performs a 2-4 second self-test and then turns off. At low speeds (under 25 mph), do you feel any brake pedal pulsation during ABS activation?

I can provide detailed wiring diagrams or relay identification if needed—just let me know.

After starting the car, the ABS light went out after 2–4 seconds as described. About 200 feet after pulling out of my driveway, the ABS light came back on solidly. I found a service manual diagram identifying the two ABS relays—Main and Pump—and will now inspect them directly.

Good luck! I’m not sure if replacement parts for this system are still available. A scan tool would be ideal to retrieve a specific EBCM code—but manual methods can sometimes reveal the root cause.

I found the issue: the ABS relay coil was functional, but there was high resistance in its contacts—likely burnt. Swapping it with the horn relay during a test drive eliminated the ABS light entirely. This explains the intermittent behavior initially and confirms that the relay failure is the root cause. Thanks for all your guidance—it helped me resolve this effectively.

That’s great news! Thanks for sharing your resolution with the community—this will help others facing similar issues on older GM vehicles.