'95 Suburban Abs Light

bronyaur · November 8, 2010

The ABS light on my '95 Suburban K1500 5.7L LS came on the other day. I did some searching on this forum and solved the problem easily and inexpensively. Here's what I did, and a couple of things learned:

Up to '95 vehicles were equipped with OBD I, and the ABS codes cannot be obtained using a code reader designed for retrieving codes from the ECM, as ABS codes are not stored in the ECM. On the ALDL connector (Assembly Line Diagnostic Link) under the dash, I took a small jumper wire and placed one end into the A port, which is located on the top row at the far right. I placed the other end into the H port, which is located on the bottom row, second from the left. I then turned the ignition key to "On". The ABS light came on during the lamp check, then went out. It then flashed twice, paused, and flashed seven more times (code 27). It repeated this sequence three times, then flashed once, paused, and flashed twice (code 12). This just indicates that it is in diagnostic mode (code 12).

I looked up GM ABS code 27 via Google and found that it indicated an erratic signal from the left front wheel speed sensor. I found some great info. on how to test the wheel speed sensor, but I had a brand new extra sensor, so I quickly changed it out (this involved removing the wheel, brake caliper, rotor, and two of the hub-to-steering knuckle bolts so the backing plate could be removed, exposing the wheel speed sensor. A cap screw secures the WSS, a bolt in the upper ball joint holds a WSS wire loom, and a second bolt secures the WSS wire to the frame). I made sure the reluctor ring inside the hub was clean, and I made sure the sensor mounting surfaces were clean. Reassembled everything and turned the ignition key to "On". The ABS light came on during the lamp check, then went out. It remained out for the duration of a test drive, and ever since. The whole process took me about 30 minutes. If you were doing it for the first time and had to dig around for tools, torque specs, etc., it might take you 60-90 minutes.

Both the reluctor ring and WSS mounting surfaces appeared clean when I took them apart, so chances are that the WSS itself, the wire, or connector was bad. Oddly, I had installed new hubs earlier this year and it came with a new sensor (NAPA Auto Parts), so the WSS was only about six months old. I replaced it with a new GM WSS I came across a few years ago.

One other thing: they sell an ABS Code Reader for GM vehicles on the Internet for between $30 and $50. It appears that all this device does is jump the A and H ports and cause the ABS light to flash as described above. A picture posted by a member showing a jumper wire from A to H saved me a lot of money.

Doing my research I found lots of questions and lots of suggestions, but very few people posted any detailed success stories. Many people just indicated they took it to a shop and it turned out that part X was bad. It is not only valuable for everyone to ask and answer questions here, it is valuable for people to describe their successes. I've had great success repairing my own GM vehicles using information I've found on this forum, and probably saved myself thousands of dollars in repair bills. My '95 Suburban has 130,000 miles on it and it's still in really good shape, despite some pretty major repairs I've had to perform on it. Most people probably would have junked it years ago. A new Suburban costs over $50,000. I don't have $50,000.

Thanks to everyone here for sharing information and taking the time to post photos.

grampadirt · November 9, 2010

The ABS light on my '95 Suburban K1500 5.7L LS came on the other day. I did some searching on this forum and solved the problem easily and inexpensively. Here's what I did, and a couple of things learned:

Up to '95 vehicles were equipped with OBD I, and the ABS codes cannot be obtained using a code reader designed for retrieving codes from the ECM, as ABS codes are not stored in the ECM. On the ALDL connector (Assembly Line Diagnostic Link) under the dash, I took a small jumper wire and placed one end into the A port, which is located on the top row at the far right. I placed the other end into the H port, which is located on the bottom row, second from the left. I then turned the ignition key to "On". The ABS light came on during the lamp check, then went out. It then flashed twice, paused, and flashed seven more times (code 27). It repeated this sequence three times, then flashed once, paused, and flashed twice (code 12). This just indicates that it is in diagnostic mode (code 12).

I looked up GM ABS code 27 via Google and found that it indicated an erratic signal from the left front wheel speed sensor. I found some great info. on how to test the wheel speed sensor, but I had a brand new extra sensor, so I quickly changed it out (this involved removing the wheel, brake caliper, rotor, and two of the hub-to-steering knuckle bolts so the backing plate could be removed, exposing the wheel speed sensor. A cap screw secures the WSS, a bolt in the upper ball joint holds a WSS wire loom, and a second bolt secures the WSS wire to the frame). I made sure the reluctor ring inside the hub was clean, and I made sure the sensor mounting surfaces were clean. Reassembled everything and turned the ignition key to "On". The ABS light came on during the lamp check, then went out. It remained out for the duration of a test drive, and ever since. The whole process took me about 30 minutes. If you were doing it for the first time and had to dig around for tools, torque specs, etc., it might take you 60-90 minutes.

Both the reluctor ring and WSS mounting surfaces appeared clean when I took them apart, so chances are that the WSS itself, the wire, or connector was bad. Oddly, I had installed new hubs earlier this year and it came with a new sensor (NAPA Auto Parts), so the WSS was only about six months old. I replaced it with a new GM WSS I came across a few years ago.

One other thing: they sell an ABS Code Reader for GM vehicles on the Internet for between $30 and $50. It appears that all this device does is jump the A and H ports and cause the ABS light to flash as described above. A picture posted by a member showing a jumper wire from A to H saved me a lot of money.

Doing my research I found lots of questions and lots of suggestions, but very few people posted any detailed success stories. Many people just indicated they took it to a shop and it turned out that part X was bad. It is not only valuable for everyone to ask and answer questions here, it is valuable for people to describe their successes. I've had great success repairing my own GM vehicles using information I've found on this forum, and probably saved myself thousands of dollars in repair bills. My '95 Suburban has 130,000 miles on it and it's still in really good shape, despite some pretty major repairs I've had to perform on it. Most people probably would have junked it years ago. A new Suburban costs over $50,000. I don't have $50,000.

Thanks to everyone here for sharing information and taking the time to post photos.

That's way cool I have a '95 Burb as well and IIRC I did a write up a while back on this very subject.If it was my thread that helped you that would make me very happy,if not that's OK too,that's what this forum is all about FYI,I replaced my rt. front sensor with one from a Trailblazer which was in a pick-a-part yard.The only difference was the way it attached to my Burb(I just used zip ties).Both fronts were still on the TB so I bought them both for a grand total of $3.00 Two years later it's still working great

p.s I love mine too

kmborland · November 10, 2010

hey, i have a 95 LD 4x4 silverado. i have the abs light on as well but could not figure out why. i thought it was bc the breaks needed to be bleed but that didnt help. i'm thinking also that since this truck is lifted with bigger tires, the previous owner re-geared but never calibrated the ecm. could this cause the abs light to come on? where did u find all the info about the light flashing?

grampadirt · November 10, 2010

Check this out,should help

ABS & ALDL connector & connector jump

bronyaur · November 10, 2010

Based on what I've read I don't think the tire size would cause a trouble code in the ABS system. I found the trouble codes in this document around page 3-12. Make sure the table you use is for your application.

Yep, Gramps. The pics I saw are in the link you provided above. Invaluable. Thank you.