The abs and brake light on my 1998 12 valve are on most of the time now. Any ideas on why or how to fix the problem would be appreciated. Thanks

 

If its the simple rear wheel ABS system,there isnt much to it.You can start by replacing the sensor in the rear diff.An easy fix,its about 30 bucks and it turned off my ABS light a while back.
Unfortunately,mine's back on now too,ands its not the sensor this time.So far I havent got any leads or recommendations on what else to check this time......

If you have 4 wheel ABS,theres a lot more to it and Id venture a guess that a computor controls it,which means theres probably a scan tool out there that can pinpoint your problem.

 

check the connection on the rear diff. (if you only have RABS). Was about to replace the sensor on the '95, but it was just a dirty connector. -- It does live in a hostile environment.

 

Here's a strange one. Had a guy bring in a '98 with the ABS light on, after several different repairs/checks nothing fixed it. Finally it turned out that the ABS light was coming on instead of the the low washer fluid light! Solution was to keep the washer bottle from running out.
Must be a pcm screw up, don't know if it applied only to this one truck or if other '98s are afflicted with it.

 

Im not sure about the 98,but on my 97 I can pull ABS codes without a scanner.Just find the scan tool connector under the dash(near your right leg) and with the key on,momentarily ground the terminal on the bottom row,second from the right(black wire).If you ground it for a second or two,the ABS light should start flashing off codes.

I got a code 7 which is "electronic control module fuse pellet open".....if only I could figure out what the h*ll that means!!

 

ABS scan codes using the above method

1- Not used
2-Open isolation valve wiring or bad control module
3-Open dump valve wiring or bad control module
4-Closed RWAL valve switch
5-Over 16 dump pulses generated in 2wd vehicles(disabled for 4wd)
6-Erratic speed sensor reading while rolling
7-Electronic control module fuse pellet open, isolation output missing, or valve wiring shorted to ground
8-Dump output missing or valve wiring shorted to ground
9-Speed sensor wiring/resistance(usually high reading)
10-Sensor wiring/resistance ( usually low reading)
11-Brake switch always on. RWAL light comes on when speed exceeds 40 mph
12-Not used
13-Electronic control module phase loop failure
14-Electronic control module program check failure
15-Electronic control module RAM failure