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BRAKE TEST


RobertWS
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I'm trying to get the diagnostic codes, but the antilock light stays on continuously after entering diagnostic mode by jumpering pins A and H.

The diagnostic info suggests that I can't get the codes if I have a continuous light. How do I get beyond this?

Thanks

Robert

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Do you mean that after I jumper A & H with the ignition off, that I read the codes without ever turning the ignition back on?????

The diagram in the FSM shows a 4 second delay with the antilock light on after turning the key on before the codes begin to readout.

I'm confused.

Thanks,

Robert

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See att for the same ABS code reading illustration from the 1988 manual. Is one of the few changes they made between years.

If no codes, when you turn the key on, the yellow light will come on for four seconds then go out.

The proceedure is like this (can see on manual page).

1) Install jumper

2) Turn key on

3) Count flashes. Will be in two sequences of one to eight with a pause between the two. I count the times the light comes on after the first four second yellow.

To read the next code, leaving the key on, remove and replace the jumper.

Continue until the light stays on steady for four seconds then goes out.

To start over from the first code, turn ignition key off then on with the jumper in place.

Once all codes have been read, the memory will clear the next time the car is driven.

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Although I don't remember, not surprising, I think the GM Teves Anti-Lock Brake Manual (the one that Barney, I and others bought a few years ago) showed using pin G. At that time, I had 89 FSM, I and others thought it was an error.( I edited my copy, long gone when I sold 89, bought 91). Your mentioning the difference, Pin G and H, for 88 vs others is, I believe, the 1st. time I've been aware.

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Just had reason to check and tried pin H first. Got steady yellow light (wonder what it was for ). Moving to G gave flashes.

Have been getting an occasional yellow lamp and pedal kick just before coming to stop. Flashes indicate RF sensor so did an R&R (takes a T-30 Torx) and cleaned gunck off. Checked ring for damaged teeth but everything looked fine. Around the block and no light or kick but was occasional and brief before. If comes back, will check connections next but have a replacement sensor on hand.

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There is no contact in the pin G hole.

There is a contact in the pin H hole connected to a tan wire.

When following the procedure, the antilock light never goes out, never blinks, never does anything but stay on continuous.

I have also observed that the main relay is never energized.

Any thoughts......

Thanks

Robert

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I have the same occasional yellow light & kick as Padgett. The flashes also indicated lost signal to RF. In the flow chart it descibes hooking up a "pin out box" to run some resistance tests. I've been trying to figure out what this is and is it necessary to have to complete diagnostics?

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Break out box would be nice (I built one for the ignition module) but in my case is easier to just R&R the connectors first. I also removed/cleaned the sensor and cleaned the teeth on the axle. If still happens occasionally, will swap sensors.

My guess is that the computer was losing the sensor signal momentarily making it think the brake had locked. This caused the thump on stopping. Very rarely it would lose the signal for a longer period and that is when the yellow light comes on. On mine the code was only found in history once (after not being reset for a long time). Evidently transients which turn the light on may not always set codes.

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  • 3 weeks later...

I diagnosed the problem to the point where it appeared that an ABS control module failure could be the only other conclusion. With the help of a replacement from Jim Finn, the yellow light problem has been fixed.

Thanks for all of the help from the discussiob group.

Robert

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