jittsl

My specBox based on a 98 2.5 with 5 speed and ABS5.3 is giving me an ABS fault that I can't figure out. It throws the code 4266 (return pump fault).

I tried running the pump with the Durametric and all I get is a relay click. I can however run the pump by disconnecting the 2 pin plug from the controller and giving it 12v (so the pump actually works). I have replaced the entire unit with a known working example and got no improvement.

All this suggests an electrical fault but I cannot find one. The two B+ wires are good as is the earth. I've checked the brake light switch and when depressed I get 12v at the unit.

Anyone have any suggestions?

Macster

4266: Return pump fault.

Diagnostic conditions: Return pump voltage and motor relay voltage actual values are evaluated and display implausible values; Open circuit to control module terminal 1.

Possible fault causes: Return pump motor locked up/runs too easily; Wire/plug connection faulty; PSM hydraulic unit faulty.

Obviously this last fault cause may not apply in your car's case since AFAIK the early Boxsters didn't come with PSM.

If you do not find an electrical reason for the behavior I think, well, my references think the hydraulic unit is defective.

Sincerely,

Macster.

jittsl

Thanks macster. So far i have:
Installed a new secondhand one in and still had the problem so I concluded I was possible that I had two bung units and that it may still be the unit.
Then tried a known working one from a friends car and still had the problem. At that I said OK it's not the unit.
I then checked every wire it was possible to check and everything came up roses.

The only thing I can think now is that I have a wire or relay or switch that responds correctly under no load but will not carry the required current under load. A bad connection or a half broken wire or something. Is that possible?

Thanks for ny help you can offer. This has been driving me nuts for a few weeks now and I'm back on the track next week. I can survive without ABS but I'ld really rather have it if I can.

Macster

Anything is possible and a wiring or other electronic component failure falls under anything.

In fact under diagnostics conditions "open circuit in circuit to control module terminal 1" is listed.

Now where control model terminal 1 is I can't say. My references do not show this.

And the info below assumes PSM control module present. I have nothing on this error for cars with no PSM control module, so the test may be useless, worse than useless, but in the hopes it might trigger a light bulb over your head... here goes:

Check ground lead of the return pump. Switch off ignition. Pull off the PSM control module plug, measure resistance between PSM control module plug pin 1 and ground. Read < 5. "5" what is not specified but since resistance it mentioned I would guess ohms.

If not ok open circuit between PSM control module plug terminal 1 and ground point of PSM. Repair wiring harness. End.

Light bulb on yet?

Sorry, but I do not mean to make light (oh, no pun) of the situation I'm just hoping you're smarter than I and the above gives you an idea cause I'm out of ideas.

Actually I'm not entirely out of ideas. There's always the old walk/trace the wiring harness and check all the connectors for any signs of issues.

Spec cars I imagine get treated to a lot of wrenching and someone at some time may have messed with a connector related to this circuit and not gotten the thing reconnected securely.

Sincerely,

Macster.

jittsl

Thanks macster. I currently have car pulled apert so I can check every wire that runs to and from the ABS. Fortunately there aren't too many and with no PSM it's fairly easy to understand what each is supposed to do or how they're supposed to respond so I should be able to find the reason.

As to your comment re wiring in a spec car. Ummm yes "people" have messed with the wiring. That would be mostly me. In all there has been almost 40lbs of excess wire pulled out of the car but generally everything that matters (the motor and the brakes - nothing else matters) has run afterwards. In fact the ABS has run all season until my last 2 races with no issue then suddenly the inexplicable. My guess is that. I've cut and joined something somewhere and it ain't quite right after a season of beating. I'll let you know.

onefastviking

Check the grounds on the left inner fender well (inside front trunk area) near back/kind of under left headlight. Take them both loose, there should be 2 large brown wires there, and make sure the paint is all clean, no corrosion and that ground wire is in good shape. They both go into wiring harness 12-18 inches from that inner well ground point and are critical for ABS ground to function properly.
Many people mess with them, or cut them out, when paring down their wiring harness. I've also had street cars that get a dirty or loose connection and then have no abs function.

It's easy enough to check and make sure, probably 30 seconds to check and make sure clean.

Report back what you find.

jittsl

Thanks Viking, I did check and although a little loose, it still doesn't pass the Durametric test. I'll keep hunting.

Todd Holyoak

Here is a copy of the factory work flow to solve your issue.

-Todd

jittsl

Thanks Todd. I've done 1&2. I'll figure out what 3 means and give it a go. I'll try and avoid 4.

jittsl

I believe I found the answer. In desperation I replaced the circuit breaker in the distribution box and the problem has gone away. I believe the breaker was making sufficient contact to allow me read 12volts at the pump but would not allow the required current to actually run the pump. May have been the breaker itself or may have been just a bad connection. Anyway so far so good.