LeSabre 1993 - Quad Driver Module A error when brakes applied

Hi all,

No hard error codes set yet. Engine will "sometimes" feel like it's missing and jerks.

If you view the datastream in realtime the Quad Driver Module A gives an error every time the brake is applied.

Could this just be the TCC Brake Switch?

Also where is the TCC Brake Switch located.

Thanks!

George

Normally this problem would be related to the TCC solenoid, or a PCM quad driver failure. I have replaced some PCM's that would correct this, however, other times we had to replace the TCC solenoid. When the brakes are applied, do you notice a down-shift out of OD? The TCC brake switch is under the dash and above the brake peddle.

Hi HotZ28!

Well I purchased a new ECM today, $89.00, and installed it hoping for a easy fix.

Well it's NOT the ECM... I got the same result when applying the brake. Still no error codes set on my Actron CP9185 scanner.

Tomorrow I will find out if the there is a down-shift out of OD when I apply the brake and let you know.

Thanks again for your help! I remember you helped me before!

George

I just returned from a test drive.

With the car in OD, pressing the brake DOES engage the TCC solenoid and results in higher RPM. So it appears the TCC solenoid in functioning ok.

But real-time monitoring of the datastream with my scanner still gives me a Quad Driver Module A error when the brake is pressed. The error disappears when the brake is released. No hard error codes are present at anytime.

I have not experienced the engine feeling like it's jerking or missing since I put in the new ECM.

Should I just ignore this error or is there something else I should look at?


George

Hi again to everyone,

The rough idle/low rpm driving did NOT go away as previously posted by me.

So here's what's happenning still....

1. No codes present
2. Myscanner realtime output shows Quad Driver Module A goes bad everytime the TCC brake switch is open... ie, when you press on the brake pedal.

(there are TWO switches on the brake pedal. One switch for the brake lights and the other for the TCC. But according to my Haynes manual it also sends a signal to the IAC!!!)

3. Engine will at RANDOM intervals run rough, like it's missing, but then fix itself. (I changed the plugs and wires, no help)

4. TCC is working fine.... road test and transmission shop checked.


OK so now my Haynes manual says that the TCC brake switch on the brake pedal DOES send signal to the IAC.

In real time my scanner shows the IAC position jump from a 70-80 range to 90-110 when the engine starts to run rough like it's missing... also the IAF temp was at 157 degrees.

My question is could the soft error on Quad Driver Module A be cause by a faulty IAC? AND could the rough low rpm idle and driving be caused by the IAC?


Thanks!!!!!!!

George

First what scanner are you using?

2nd, in some scanners this is a program glitch... And the Quad driver module you see as bad when you hit the brake is a goof in the program, not actually a bad quad driver..

Hi Jrs3800!

Thanks for the reply!

I'm using an Actron CP9185 with updated firmware.

I've had it for about 8 months. I have real time test drive recordings made by the scanner prior to this NEW problem. The saved recordings show no Quad Driver Module A errors when the brake switch was on.

George

What are all of the items on that quad driver circuit?

Hi again,

1993 LeSabre Quad Driver Module A controls:

1. Low Speed Fan
2. Evap Purge
3. Temp Light
4. TCC Apply

I've gotten the above information from the internet.

I just have the Haynes manual which does not specify in it's electrical schematic which components comprise each Quad Driver Module sadly....

I don't have the 1993 Service Manual yet.... but I just bought one online, should be here next week.

George

UPDATE:

I am still getting

1. No hard error codes present
2. My scanner realtime output still shows Quad Driver Module A goes bad every time the TCC brake switch is open... ie, when you press on the brake pedal.

BUT I DID....

buy and install a NEW IAC. It was a success. The engine does not have any more rough missing low rpm problems.

My IAC opening in park is now 0 instead of 60-70 in real time monitoring with my Actron CP9185 scanner.

So the old IAC WAS NOT FUNCTIONING PROPERLY!

But how is one to know if you DON'T HAVE THE ACTUAL SPECS?

CLEARLY if you do not have the factory specs for every electronic monitoring module, sensor, switch, solenoid, etc.... connected to the ECM on this car, you are just guessing.

(Which is what my BUICK DEALER was doing and they should have had this information! They just wanted to replace EVERYTHING, about 8 sensors, modules and THE ECM... and it MIGHT FIX THE PROBLEM..... __MIGHT__ ....can I repeat that once again... _____MIGHT_____)

CLEARLY the manuals available to the public like "Haynes" and "Chilton" are 80% worthless.

I have ordered __THE__ "1993 Buick Park Avenue, LeSabre Factory Service Manual" ... I PRAY this has got some REAL information which I can actually use to properly diagnose sensor, module, switch, etc problems which send data to the ECM.

( I mean like the IAC open position in real time with the car in park should be "______") This is real time data spec sent out by the ECM to any good scanner.

Without this kind of information, you are just guessing. I HATE guessing. :screwy:


George