1994 Blazer Sport Full Size (2 door) started having intermittent ABS light issues a few weeks ago while out hunting. On the way home from the woods last saturday, after I shut it off to close the gate, when restarted the speedometer started jumping around and then the truck wouldn't shift out of second gear. I drove 15 miles back home like that.

Codes pulled are 37 and 28. Kelsey-Hayes 4WAL system and code values are difficult to find for this system. I think the 37 code is rear wheel speed sensor related and the 28 code is front sensors. Don't know if this system has a buffer or not (apparently some do and it's located behind the glove box by the ECM?)

What I have done:

Cleaned all 3 speed sensor connections and verified front speed sensors with ohm meter and AC volts. Checked ok.

Rear sensor was replaced this morning since I bought a new one. Old one had a few metal shavings around the base where the black plastic head meets the metal threads. Cleaned and ohm check at 1430 so within spec of 1000 to 2000 ohm. Read someplace that metal shavings can cause false readings on VSS.

I cleared the codes before I left the house and drove 4 miles to the store. Speedometer worked fine but half way there the ABS light came on. On the way home the speedometer started jumping around again and back to the 2nd gear issue. Read the codes again and 37 followed by 28 came back up.

Pulled new sensor and flushed transfer case. Ohm checked at 1330 on new sensor. No metal shavings.

At a bit of a loss on this?.?.

Elk season starts tomorrow morning and I need my rig fixed.

Please give me a clue as to what to do next.

 

Thanks for all the feedback on this issue over the last month. Helped tremendously...

After checking all grounds, any bare wire issues and and connections by adding dielectric grease for prevention, it all came down to a bad VSSB board, Hit the local bone yard and pulled one off a 1994 suburban, plugged it in and best shifting and overall performance to date.

HMFFP

 

Back with the same "trans in limp mode" issue as last year.

While driving about 10mph and applying the brake lightly, the abs pulses. Can't feel it in the pedal, but I hear it under the hood. Eventually the ABS light comes on and code 28 pops up. This all started after I bled the brakes on all 4 corners.

In order to determine which speed sensor was producing the code I kept driving it. The result was codes 36, 37 and 28. The 36 and 37 relate to left rear speed sensor voltage and erratic signal loss.

Within 10 miles of retrieving those codes the limp mode situation occurred.

Any insight out there?

If the DRAC was not calibrated for a different tire size would that cause an issue with the ABS or just transmission shift point?

I'm suspecting the DRAC is toast again.