I found this thread while searching for a solution to my ABS light on problem.

I' ve checked for codes and get:

27, 66, 86, 12, 25, and sometimes 26.

When I reset the light, turn off, turn ign. on. (engine off) the system does its self test and returns with the same codes. I can hear the ABS unit turn on and off, btw. I've checked the front left sensor resistance and it checks out ok. Some of the other codes are related to the hydraulic/electric unit.

I know there's a particular order with which codes to takle first, but don't know this order. I've attached the two pages applicable with the codes listed. This is from a user's manual for one of those code retrieval units that plug into the diagnostics port.

Please help - I'd like to get this thing working if at all possible (I like a challenge).

 

If these codes were obtained by using the paperclip method and watching the check engine light, then here are the descriptions for what codes I could find on TroubleCodes.net. I would have to look in my references which are at home to determine what the other codes are. The images that you show from a code book are for dedicated ABS codes which must be obtained by scanning the ABS module separately.

12 - OBD1 system normal
25 - ??
26 - Quad-Driver sense voltage shows a low voltage when battery voltage should be present, or if the sense voltage shows battery voltage when a low voltage should be present for at least 5 seconds when the engine was running.
27 - 2nd gear switch was closed or grounded for 10 seconds when vehicle was in 4th gear, or 2nd or 4th gear switch was open when engine was first started.
66 - 3-2 Control Solenoid Circuit Fault .
86 - ??