PSM off and ABS indicators coming on

[gcp05]

Recently both “PSM off” and “ABS” indicators starting coming on simultaneously after starting and driving for a short time. I have a 2001 base with 15k miles. Sometimes they come on after only a couple minutes; other times it takes 10-20 minutes or so. Faults are cleared by simply turning the engine off and restarting but eventually both lights will come on again. No real rhyme or reason – doesn’t seem to be associated with hard breaking or acceleration. It’s been happening intermittently but lately just about every time I drive the car.

Appreciate any thoughts. Thanks.

[Brokenleg]

I have the same thing happening on my turbo. I read one post that found that one of the break sensor lines to one wheel was being hung up a little by the drop link bolt. It would pull the wire tight enough that the signal was interrupted and the ABS sensed a fault. I believe you get the PSM fault any time there is a fault in the ABS. I have also seen posts that link the ABS and PSM lights to the MAF faulting? Mine happens at start up, and if I switch off and restart it goes away for a day or two. I suspect the cargarfic chip in mine.

[carreratime]

Hi gcp05,

Check the brake fluid level. It's possible that you are getting a faulse warning because the low level trips the sensor when you accelerate. It's probably time to change the brake fluid anyway:)

[adsach]

You might get some more data if you have someone read the OBD-II codes.

[Loren]

You might get some more data if you have someone read the ABS and PSM codes - which will take a PST2 or PIWIS tester.

[gcp05]

You might get some more data if you have someone read the ABS and PSM codes - which will take a PST2 or PIWIS tester.

<{POST_SNAPBACK}>

Thanks for the suggestions. Brake fluid is ok as it's at max level. Looks like I'll need to get the codes read.

[Loren]

Where are you located?

[gcp05]

I'm in New Jersey.

[Loren]

Find a shop with a PST2 or PIWIS tester and have them read out the ABS and PSM codes. Unfortunately, until you do that you are shooting in the dark.

[deliriousga]

I recently went through the same type problem on the 928 that turned out to be a shorted relay. I was looking at the Boxster relay charts and don't see one for the ABS system. Is this the case?

Anyway, I'm with Loren if there's no relay (i.e. simple check/fix). Pay someone a few bucks to read the system and give you more info.

One thing that is common over time (though not usually only 15K miles) is dirty ABS sensor ends. The metallic particles from the brake pads stick to the magnetic sensor. In the 928, they were so dirty they could not feel anything at highway speeds and it shook the car like crazy. Cleaned them up and, voila, the shaking disappeared. Clean them when you change the pads and you won't have any future problems due to dirty sensors. :D

[gcp05]

Do the fault lights need to be on when the PST2 or PIWIS tester is hooked up or are the codes stored in some kind of memory? Thanks.

[Loren]

Do the fault lights need to be on when the PST2 or PIWIS tester is hooked up or are the codes stored in some kind of memory?  Thanks.

They should be stored in memory - regardless of the current light status.

[gcp05]

PST2 tool reports fault code # 4460 - PSM pressure sensor. Does anyone have the Porsche procedure to troubleshoot a 4460 fault?

I read on PCA tech site that someone with the same fault had the dealer replace the brake switch, clutch switch, the ABS control unit and pump, and the brake fluid resevoir and after only 3 months of trouble free driving, the ABS/PSM fault has reoccurred.

Would appreciate any input on the most economical way to approach this. Thanks!

[Loren]

PST2 tool reports fault code # 4460 - PSM pressure sensor. Does anyone have the Porsche procedure to troubleshoot a 4460 fault?

I read on PCA tech site that someone with the same fault had the dealer replace the brake switch, clutch switch, the ABS control unit and pump, and the brake fluid resevoir and after only 3 months of trouble free driving, the ABS/PSM fault has reoccurred.

Would appreciate any input on the most economical way to approach this. Thanks!

Here is what the manual says for possible causes. The stop light switch (see Note) seems a likely cause.

The manual has details for testing including voltage/resistance measurements - 8 steps in all.

- Short circuit to ground/B+ or open circuit

- Plug connection on stop light switch faulty

- Incorrect adjustment of the stop light switch

- Wiring/plug connection between pressure sensor and control module faulty

- Pressure sensor faulty

Note:

A malfunction of the stop light switch can cause this fault. The stop light switch must have switched before a brake pressure is recognised. When the brake pedal is actuated, the stop light switch and the brake lights are triggered. The brake pressure on the pressure sensor is 0 bar.