I was disconnecting my battery last night and managed to touch my wrench across the battery positive terminal to the ABS computer case. After a small spark and an "oh %&$!" moment, I figured I probably fried the ABS computer.

Turning the car on the ABS, Brake and center diff light turned on along with the alarm buzzer. Shut the car down, pulled out the ABS computer and checked fuses. Everything looked good. Plugged it back in, started the car up and voila! All the lights went away, or so I thought.

On the commute to work today the "Brake" and center diff light were constantly blinking in about a 1 second interval. I decided to see if the ABS worked and locked up the brakes, which caused the alarm buzzer to go off, and turned the ABS light and other two lights on solid.

Question is, did I destroy the ABS computer beyond repair? Is there anything else I could have fried instead/as well?

Does anyone in Calgary have a C4 that would be willing to swap computers with to see if thats the real problem?

 

Isn't the ABS computer on the opposite side of trunk as the battery? How big of a wrench were you using?

Did you check all the relays? Could have fried the R34.

What year is your C4? If it's over 91 and up (think that's the year), you can get the fault code without a Bosch Hammer.

Here's the procedure:
http://www.durametric.com/porsche964faultcodes.aspx

May give you a direct answer to what happened.

Electrical issues are such a PTIA. I currently have PDAS and ABS lights to deal with.

 

Car is an 89.

The PO relocated the unit upside down to prevent water getting into the connector, maybe thats why it's within reach? The wrench was a standard size, maybe 5" long?

 

Ahhh, yeah explains why it happened.

I also have an 89 C4.

 

sorry to hear that 1.O - gladly you aren't the only one to make that mistake - although my airborn wrench
grounded to the hood latch and immediately fried the latch cable through!

Do you have Tore's cable and the free scantool software - might be able to telll you something although I'm not sure the ABS ecu
is actually linked into odbII other than the wheel speed sensors.
see here

Made some hard to remove/lose battery terminal covers to make myself feel better afterwards, and put in the
secondary release cable too.

 

Where do you get this software? I'd love to try this.

 

I've got a durametric, will scan tonight.

I've been doing some searching and it appears that the R34 relay can fail from an over-voltage condition quite easily. I will be trying to jump the relay to see if that cures the problem. Fingers crossed.

http://forums.pelicanparts.com/porsc...iff-light.html

https://rennlist.com/forums/964-foru...-1990-a-2.html

 

see the thread I posted above or search TORE scantool

 

I did, but the link to the software that is on the thread is dead.


Yeah, I think you may have fried your R34. That was the first thing that came to mind when you mentioned what happened. I think you can bypass it to check if it or possible dismantle it (not sure on this) to see what the inside looks like.

 

Found it:
http://www.bergvillfx.com/index.php/...4-and-993.html

 

For future reference, always disconnect the negative terminal first. It makes it impossible to fry anything, since you do not have a complete circuit on the positive side, and the negative side is obviously already grounded.

 

Yep. Learned that one the hard way. Cant wait to get home from work and try to fix this thing now!

 

Relay wasn't the culprit unfortunately. I've found a rennlister locally that's willing to lend me his abs computer to see if that's the problem. Not sure if I want it to be the cause or not considering how much the silly things cost.

 

lightweight project continues - ABS delete is always an option
although maybe not up there in sleet land

 

ABS module for sale. No affiliation.

http://forums.pelicanparts.com/porsc...ml#post8609388