1994 Firebird 3.4L (210K miles): ABS INOP light stays on

Chaud

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#1
Well, I am back again for another problem. Thanks for helping me to resolve my ignition problem last time. Yesterday "ABS INOP" light came on the instrument panel and would not go off while driving. Key observations are as follows:
1. Ignition on but not cranking, all lights including ABS come on and go out after few seconds. But ABS light comes back on again and stays lit.
2. With multiple on and off starting, I get the same results and ABS light comes on.
2. CEL ( check engine light) is on but can not be read unless a special instrument is used. I have tried reading the codes before by shorting data pin with ground but "no light flashing" and nothing happened. It is some kind of modified version of OBD1 and OBDII. So it is a dead end to read the code.
3, Even with ABS light on, car runs fine.

Appreciate your help if you know where should I look or how to diagnose this problem.
Thanks-Chaud
 

Gus

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#2
'94-'95 years were transistion years......not all code readers and scan tools can read them.....of course, GM tools can....

As for the ABS, unless you see something from a visual inspection, you basically know nothing....need to have the code read to have a starting point....same with the CE light.....
 

Chaud

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#3
Thanks Gus. I agree. I doubt dealer will read the code for me free but there is no harm checking it out. I will do the visual check and see what I find. It will be wonderful if I could spin each wheel and read the voltage/pulse from each of the sensor attached to wheels. Any other idea I would love to hear about it.
Thanks-Chaud
 
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#4
Too many variations in this era of ABS, have to play with it. Some use RAM that can be reset by disconnecting the battery or are reset automatically when the problem is repaired. Others started using flashram that either has to be reset by a procedure or with a scanner. Shop manuals are worthless in this respect for explaining which system is used, but useful in showing all the error codes and the circuit diagram.

Typically, if the ABS light comes on and stays on with the ignition switch, you have a static error and can be found by using just an ohmmeter, like open or shorted wheel sensors, ABS and pump relay solenoids. Not an easy task if your ABS module is located high up in the dash, need access to its connector. Dynamic errors occur if the lamp comes back on when the vehicle reaches about 5-8 mph, this is when you need a scope to find the problem. Key error is a differential opposite side speed error, more or less pulses where they should be equal.

Just had a tree limb and power line breaking icy rain a couple of days ago, ABS is completely worthless under these conditions and will never replace outlawed studded snow tires. But some nitwit statistical mathematician determined that ABS is 14% more effective in stopping vehicles than vehicles without ABS. So standard equipment on all new vehicles. To me, just more problems, only safe way to travel under these conditions is to hold your speed down to 2 mph.