ToreB

Hi guys.
I have a '94 C2 with ABS control unit part number 99361812500. The ABS warning light comes on from time to time, and I cannot find the reason.
It is not possible to contact this unit with any Porsche OBD diag tool. Does this early 993 have the same limitation as the 964 C2's, no on-board diagnostic possibilities? This ABS control unit is different from the 964 C2.
All tips welcome.
Cheers,
Tore

Patrik S

Tore,
Are the speed sensors in the wheelhub ok?
BR Patrik

il pirata

Adding to what Patrik said, does this only occur when the car is moving?

As to a 1994 having ABS on board diagnostics, I have seen posts in other places indicating yes, here's one:

http://www.911uk.com/viewtopic.php?p=483929

Have you tried using a Hammer or similar?

pp000830

It will come on from time to time during driving when the system senses wheel slip. You can also feel it in the brake peddle when it is actuated.
Durametric can run the ABS OBD Codes and can tell you which sensor has a problem.
I suspect in most cases just cleaning the 4 sensors' plugs on each strut will solve most sensor issues, unless a rotor or hub was recently disturbed altering the sensors' proximity to it's reading ring.
My experience was with the ABS relay(s) in the trunk. I had problems with the system only once and replaced the two inexpensive relays in the frrunk and resolved the issue.

nine9six

Tore,
I'm pretty sure the Bosch Hammer that you sell will do the trick, if you have an OBD1 port.
Please advise, if the Bosch Hammer does not...
Thx in advance.

ToreB

Thanks guys.
As mentioned in my initial post, there is no OBD connection to the ABS control unit using Scantool, Porsche hammer, PST-2 or PIWIS.
The ABS lamp sometimes comes on at start, sometimes when driving.
I dont' like to change parts or do other actions without proper diagnosis. Since yesterday, I have dug up the '94 (and '95/1) schematics, and see that the ABS unit in question does indeed have a OBD connection. (K and L wires) I'll start fault finding on these wires to the unit to see if I get a Porsche diag tool connection.
Cheers,
Tore

Endoman

I've been having exactly the same problem on my car also a '94 model.It happens more often when it's raining. Ign. off, restart and it does not happen again for a while. I will follow this thread with interest. I suspect a corroded electrical contact somewhere in the system but these intermittant electrical problems are a real pain to find.
I had an occasional misfire on my 944 everytime I took it into the shop it was working fine, on a hunch I replaced the crank sensor et voila.
But as you say you can spend a lot of money with trial and error, Tore.

ToreB

Endoman, thanks.
I have tried most of the intermittent contact suspects, ABS control unit connector, both ABS relays and the instrument clock connector. All have been inspected and reseated several times. What irritates me that the cause might be stored as a fault code in the control unit, but there's no diag contact. Yet.
Cheers,
Tore