95 Suburban ABS light-may have codes-??

I have a 1995 Suburban LT 4WD and my ABS light is on. It went off a few times when on wet pavement and the ABS engaged, but came back on a short time later. Lately it is on constantly. A guy hooked up a scanner to it for me but he admitted he wouldn't know what the codes would mean. That made me a little skeptical, but was greatful for any help. So I'm wondering if these codes mean anything to anyone here?? The codes he said his scanner detected were: 23, 12, 21 and 22. Any ideas or input to this problem would be greatly appreciated!! I do almost all of my own work, but I don't know what part of this ABS system to start looking at... John

12 = Diagnostic mode
21 = TPS circuit (signal voltage high)
22 = TPS circuit (signal voltage low)
23 = not shown in my book
I have a 95 with 350 and try to do most of my own work, but the only manual I have is a Haynes. Not all codes apply to all models.
I retrieve any stored codes from the ECM memory by sticking a bent paper clip into the wiring connector under the dash on the drivers side, with the engine turned off.
One end into the diagnostic terminal (B) and the other end into the ground terminal.
Turn the ignition on (don't start) and watch the SES light. Count the flashes and look up the codes in a book. This is 95 and earlier OBD1 stuff but can still be real helpful. Get some kind of manual, even if is a cheap one like my Haynes. Good luck.

[QUOTE=jimh]12 = Diagnostic mode
21 = TPS circuit (signal voltage high)
22 = TPS circuit (signal voltage low)
23 = not shown in my book
QUOTE]

Thanks for looking that up. What is the TPS circuit? Does it have anything to do with the ABS? I will also try the paperclip and try to get a fresh set of codes. Thanks again.

Unfortunately you may have been given some incorrect information..
You are looking for information regarding the ABS codes 12,21,22,23...the information you were given was for ECM trouble codes...
If I get time wednesday, I will post the proper answer to your question about the ABS codes

Thanks Merlin, I'd appreciate any input you may have. I'd like to find and fix the problem. Also, Jim, thanks for your input from that Hayes Manual. I appreciate any help that I can get, it's all knowledge!! John

Rumor has it that Merlin is one of the BEST in the business. Sorry for the incorrect information.
Jim

Rumor has it that Merlin is one of the BEST in the business. Sorry for the incorrect information.
Jim


Jim,
no fault,no foul..we are all human..And don't believe everything you hear..I'm just a humble GM tech...

Now, on to our ABS problem..ABS DTC's 21,22,23 all have to do with the right side wheel speed sensor...check the resistance of the sensor..should be between 2500-3500 OHMS (depending on temperature).
Inspect the harnesses good for signs of exposed wires or bad connections.
Look at the sensor and the tone ring for signs of damage.

"Now, on to our ABS problem..ABS DTC's 21,22,23 all have to do with the right side wheel speed sensor...check the resistance of the sensor..should be between 2500-3500 OHMS"


Thanks Merlin!! I'll have to check that. One question though, is there a wheel speed sensor on each wheel or just one for the right side - one for the left side? John

That system is considered a 3 sensor/channel system..there is a WSS for each front wheel and the rear wheels get their signal from the speed sensor in the transmission