# 1994 Z28 BRAKE and ABS INOP lights



## raylo32 (Nov 25, 2006)

1994 Z28, M6

I had been having intermittent ABS INOP until a couple days ago but now I have a constant ABS INOP light as well as a BRAKE light. Brakes are fine otherwise, fluid is full, no leaks so I don't think the BRAKE light is related to brake circuit pressure differential.

So I suspect the problem is the ABS electronic module as my first guess, then the main ABS hydraulic/motor unit as my second guess. Oh, I tested the e-brake switch to see if that was giving me the BRAKE light and it was working properly. And I tried another relay in the ABS socket and it didn't make a difference.

Anyone know how best to approach diagnosing? Since it is 1994 and OBD-1 I am not sure there are any brakes codes available.

Bruiser, are you around? What do you think? I have also cross posted this to a couple of the Z28 forums... hopefully get some help there soon.


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## Windows on Wash (Aug 30, 2011)

Does the cruise control work?

Check the rear spoiler lights.


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## raylo32 (Nov 25, 2006)

Yes cruise and the third eye work. Now just this AM after 3 days and after stopping and parking twice on different errands the BRAKE and ABS INOP lights cleared on the third driving leg. Then I tested the system with some hard stops and it works fine. <scratching head> but hopeful this keep working.



Windows on Wash said:


> Does the cruise control work?
> 
> Check the rear spoiler lights.


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## WyrTwister (Jul 22, 2013)

Should be able to clear the codes by disconnecting one of the battery cables .

Google reading codes on OBD I by jumpering 2 pins / terminals on the OBD I connector .

I have a 91 Caprice with OBD I . I have an OBD II code reader . I have been looking at ebay for a OBD I to OBD II adapter cable . Any one have any experience with something like that ?

I recommend you buy a Chilton or Hayes manual for your car . That has wiring diagrams .

God bless
Wyr


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## raylo32 (Nov 25, 2006)

I have TTS Datamaster and it reads codes but it doesn't show brake and ABS DTCs. I just found a program called scan9495 over on Camaroz28 forum and it does show ABS codes but by the time I tried that the errors had cleared so no ABS DTCs present. Hopefully it will stay that way.


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## Windows on Wash (Aug 30, 2011)

Could be an ABS sensor (wheel reluctor) as well.


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## raylo32 (Nov 25, 2006)

Yes, I figured that was probably what was giving me the intermmittent ABS INOP all along but no way really to clean them. The fronts are in the hubs and the rear (only one rear since 3 channel system) is in the diff. But those instances did not throw the BRAKE warning light.



Windows on Wash said:


> Could be an ABS sensor (wheel reluctor) as well.


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## WyrTwister (Jul 22, 2013)

Some vehicles store the codes , even if the idiot lites go off , all by then selves .

God bless
Wyr


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## Brainbucket (Mar 30, 2015)

On the 91 Caprice, With key on, ground A and H pin together (A upper right, F upper left, G under F lower left, M lower right under A,) on the ALDL connector and after 3 sec anti-lock light will flash code 12 (ready to continue) first then will flash first digit then the next digit then pause then next code untill code 12 (done with codes) flashes again.
On the 94 Z28 with a newer trans cause 5 speeds came out in those, looks like you need a scanner to read codes. Now sometimes I found the light flashes for a while when you turn on the key on some cars. If it is flashing before it goes on steady, it is flashing codes normally.:vs_cool:


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## WyrTwister (Jul 22, 2013)

Yes , I have done that on the 91 Caprice . The codes and the procedure is in my Chilton or Haynes book . Along with the wiring diagram .

God bless
Wyr


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## raylo32 (Nov 25, 2006)

I used to do that back in the day but have used software for the last 15 years or so. Besides, the PCM codes available that way do not include ABS codes. You need to access the EBCM to get those. I now have software to do that... but the light is off again so there are no codes (my software doe not read stored ABS codes, have to be active codes).



WyrTwister said:


> Yes , I have done that on the 91 Caprice . The codes and the procedure is in my Chilton or Haynes book . Along with the wiring diagram .
> 
> God bless
> Wyr


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## raylo32 (Nov 25, 2006)

Well, this is resolved. I got a reman EBCM (ABS computer), popped it in, and system is back online 100% of the time so far... 3 days and counting. No warning lights and ABS functions properly. OEM EBCM might have had a cold solder joint or somesuch. Although I probably should have tried cleaning and reseating the connectors on the OEM unit, like I did for the connectors under the hood and at the wheels. But I had already ordered the reman by the time I got under there... and it was a PITA to R&R, especially with my big hands.

I also replaced the coolant level sensor in the radiator and got rid of that light. I just had to get those lights off, after giving my brother such a hard time about his BMWs always having a bunch of dash warning lights on. That stuff just drives me nuts.


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## Bob Sanders (Nov 10, 2013)

My abs screwed up. After hearing how much it was for the parts (pressure control module) I fixed it with a piece of electrical tape over the abs warning light


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## raylo32 (Nov 25, 2006)

Yes, the main ABS hydraulic/motor modules are $$$. Remans for my car are ~$1400. And the work to install with Tech 1 tool to bleed is probably $500. If mine had been bad on this old car I probably would have used the tape mod, too.


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