Cody D

Okay I'm having a fair bit of trouble tracking down the cause of my PDAS and ABS dummy lights being on, I'm using my 964 workshop guide by Adrian Streather and every test I did failed.

Here are the two lights that are ALWAYS on. (As well as the ! and the park brake light).



First thing I tried was testing for voltage behind the PDAS control beneath the dash, these are the two connectors that I tested, but I couldn't get any voltage reading from either, does the car have to be on? I had the key turned to run but I didn't start the car.





Second test I did was the resistance across pins 1 and 3 on the ABS system longitudal (sp) plug. I set my tester to Ohms and 2k and across pins 1 and 3 I got 0.002 and across pins 2 and 4 I didn't get any signal.



The problem could be my lack of knowledge of testing resistance, the manual for my tester says that the 2k setting is what I need to use (I think), here's a picture of my testers OHM section.



This post may be jumbled but I've spent the last couple hours trying to test things and failing miserably, any help would be much appreciated.

Cody D.

Indycam

Does the abs work ?
Is the parking brake light always on ?
Hows the brake fluid level ?

Cody D

I've never felt the ABS kick in, is it fairly obvious?

The parking brake light is not always on.

Brake fluid is full.

Indycam

"I've never felt the ABS kick in, is it fairly obvious?"
Find a slick spot , jam on the brakes hard hard , try to lock them up .
If the abs works , you will feel it doing a thump thump thump sort of feeling .
When it kicks in , its obvious .

"Brake fluid is full."
The brake fluid level switch in the brake fluid res cap can turn on some lights on the dash when the brake fluid is just a little low .

"The parking brake light is not always on."
Does it come and go with the parking brake use ?

So I went and looked at a google map for Olds, AB, Canada ,
do you know everybody in town ?

Cody D

I'll go try the ABS now.

The brake fluid is right up to max, I'll add a bit more just to be sure though.

Yes the parking brake light goes on and off with the application of the parking brake.

I just moved here so I don't know anyone actually, but I'm sure they noticed the new guy with the 911 and the NSX, they probably think I'm a drug dealer, haha.

Indycam

Dude can I score some blood pressure pills ? Glaucoma drops ? I got cash !

Cody D

Well the ABS definately does not work, the brakes just locked up and I slid on the ice.

Shhh, keep it on the down low, haha. The only thing I could supply you would be heavy crude oil, how about 60,000 bbls of that? It's $1.00/bbl now so it's worth lots, haha.

frankvan

First off it's always great to welcome another Alberta Rennlister!

As for the PDAS/ABS issue I just spent the last six months troubleshooting mine and had pretty much done everything - cleaned all the connections in the entire system, replaced relays, topped up fluid, etc... all to no avail. Last month I replaced my coils (thanks Dave ) and haven't had any lights since! Even though the ignition coils and PDAS/ABS controllers are at opposite ends of the cars a bad coil or any noisy part of the ignition system can cause havoc with the apparently sensitive electronics.
Have you tried unplugging one ignition module at a time to see if the car runs rougher or not at all. Running just one coil or the other you might find that the PDAS lights don't come on at all (as I did).
Check out https://rennlist.com/forums/964-forum/375433-what-effect-to-coils-have-on-power.html for good coil pics. If you do disconnect a module be sure that you disconnect the ignition module connector - don't disconnect any of the high tension leads!
Also check out the many threads for PDAS/ABS lights such as https://rennlist.com/forums/964-forum/388825-89-c4-with-interlock-and-abs-warning-lights-and-buzzer.html

Good Luck!
(btw, these cars are scary without ABS in the snow - they still get great accelerative traction but stopping )

Have you posted any pics of the car yet? It's a Rennlist necessity.

Cody D

It's late so I'll give your suggestions a go tomorrow, but I can throw up some pictures tonight before I go to bed.

BTW, are you going to the Norden Suspension Tech night in Edmonton on January 16th?

Here's my intro thread, I'll put pictures in there.
https://rennlist.com/forums/showthre...25#post4394325

Indycam

When my cars abs didn't work , I cleaned up the connector to the abs computer and it started to work again . Have you had a look see at that ?

Cody D

Is that in the passenger side of the front of the car beside the spare tire? I checked one plug there and it was completely clear. It was a smaller plug. I'll go look in the 964 book and check again.

The other thing I'd like to check is the sensors, I've read that cleaning certain sensors can help. I also will go get some brake fluid just to make sure it's topped up.

gfunk

The longitudinal accelerometer often gets clogged up with metal filings and will prevent the ABS from working but it normally doesn't set off any warning lights. It's probably a good idea to check in any case but I don't think it will fix your warning light issues.

Greg

Indycam

https://rennlist.com/forums/attachme...1&d=1200203838

The abs computer is in the alu box on the left hand side of this photo .
The big connector atop the box is a funny thing .

Cody D

Okay so now I've checked the connector on the ABS controller, it looked fine. I tested the voltage on Pin 1 to the ABS controller with the key on (not running) and it read 0.58 volts. I almost think that wires are disconnected or something.





I also disconnected the coils one at a time while the car was running to see if there was any problems with each of the coils. They were fine.

Next I'm going to take the wheels off and check the ABS speed sensors.

Cody D

Well after testing pretty much everything I think I've found the cause of the PDAS/ABS lights and buzzer.

While checking the ABS speed sensors, I found they were fairly dirty so I spent some time cleaning them, but when I got to the last one I found a problem. The first picture is the drivers side sensor, the second and third are the passenger side sensor, the nub is completely broken off. I guess I'll phone up the dealership tomorrow and hopefully they'll have one in stock (good luck).