Parking Break Light Code

[Jerther]

I built myself a cable to connect my laptop to the ALDL connector of my truck...

 

I plugged it in the ALDL connector but not on the PC. The cable plug shows activity so it seems ok.

 

Now, my parking break light keeps on flashing 9 times in a row, pause, and flash again.

 

I didn't put the 10K ohms resistor on the connector to swet the ECM in ALDL mode, but i guess it set itself automaticly to this mode because the idle is pretty high and i hear some knock, caused by the electronic timing control being disabled in this mode...

 

Now, how do I set my ECM back to normal operating mode?

[GM-Tech]

The park brake light has no connection to the ECM. You've probably somehow jumpered terminals A to H in the data link connector, or just grounded pin H. This puts the ABS (RWAL) into diagnostic mode, which flashes codes using the park brake light.

 

I think you best recheck the cable you made.

[Jerther]

Oh, interresting!

 

Yes, I thought I could use pin H as a 12v source. I'll find one elsewhere.

 

Do you know a place where there is a list of those ABS codes?

 

And how do I set the ABS to normal mode?

[Jerther]

If the ECU has no stored any trouble codes, the technician will cause the ECU to store a code 9 by grounding the wheel speed sensor signal at the ALDL connector terminal "H". As the end of the diagnostic procedure, the memory of the ECU must be cleared, This is done as follows:

 

    * Turn the ignition switch to the OFF position.

    * Remove the fuse from the ECU trouble code memory power.

    * Wait for at least 10 seconds.

    * Reinstall the fuse.

 

Complete info: http://www.raybestos.com/OnLineTraining/abs-221.htm

 

Alright!

 

Thanks for the useful info though!

[redvett]

1988 does not have ABS it has RWAL = rear wheel antilock. Just unplug the module under the M/C with ign. off and replug it. Code is gone if there isnt a problem. OBD1 does not have 12v at the ALDL. Only OBD2.

[GM-Tech]

1988 does not have ABS it has RWAL = rear wheel antilock.

 

A technicality. ABS is an anti-lock braking system, and since RWAL is a rear wheel anti-lock braking system, one could say it is ABS, albeit, only in the rear.

[Jerther]

1988 does not have ABS it has RWAL = rear wheel antilock. Just unplug the module under the M/C with ign. off and replug it. Code is gone if there isnt a problem. OBD1 does not have 12v at the ALDL. Only OBD2.

 

<{POST_SNAPBACK}>

 

 

 

I got my 12V from the fuse panel just above the ALDL connector.

 

I think the protocol of my truck uses a 0-5V logic... that shouldn't prevent my device from working.

 

I'll post my results, as well as my schematics here once I get it working. If anyone gives me some web space, i'll also include some videos and build a nice page

 

As for my initial post on this topic... i said I heard knock and high idle..... duh... really... my hesitation/stumble problem is driving me crazy... I'm starting to hear sounds where there aren't...