re warning lights

[carrera4s]

Around a week ago abs and psm warning lights came on on my 996 turbo then after a while extinguished themselves,then was ok for a while.Then next time of going for a drive came on again,went to have a diagnostic check no fault codes came up.Then went out again at weekend after driving for over a hour came back again,when it has been stood idle for a couple of days warning lights as i said extinguish themselves,went for another drive came on but by the time i went back over to my indy gone off no faults found.Its a bit like toothache when you arrive at the dentists chair the pain has gone.I know i have read posts before on these faults,is it a matter of waiting until they are on all the time.
Kind regards Brian

 

[NXI20]

MAF & brake pedal switch, in that order, are the usual culprits.

 

[Richard_Hamilton]

I would add an ABS sensor to the list, but as the problem is intermittent, it could be just a bad connection to one of the ABS sensors.

 

[DaveS]

ORIGINAL: Richard Hamilton

I would add an ABS sensor to the list, but as the problem is intermittent, it could be just a bad connection to one of the ABS sensors.

I too have the ABS/PSM warning light on my 996 02 Targa. I have had it diagnosed as the brake pedal switch. I have purchased the part. My question is how easy is it to DIY fit? I have very limited technical ability!!

 

[Richard_Hamilton]

The switch unclips from the bracket with a bayonet (1/4 turn) action. It is a bit awkward to get to, as it is buried up in the pedal box. When refitting the new switch, pull the plunger all the way out before pushing it into the bracket.

 

[DaveS]

Richard,

Thanks..having pre MOT check on Friday so will get help from my friendly local mechanic if needed. Can I just say as someone new to the forum I am impressed by the level of technical knowledge & support available..invaluable to people like me who know little about the mechanics of these cars.

 

[jml3p]

Try the brake light switch
Rgds
jl

 

[DaveS]

Fitted new brake pedal switch & passed MOT...today..2 new rear Conti Sport contact2s needed to pass but given weather today rather glad to have new rear rubber. Unfortunately although my MOT mechanic fitted the new switch & cleared the fault on his diagnostic device, the same fault code has come back. Very annoying! Will now have to take my car back to my Porsche indy to see if his Bosch unit can clear the fault. Anyone got any better ideas?
Dave S

 

[Richard_Hamilton]

What was the actual fault code number?

 

[DaveS]

Richard,

Porscheshop did their best on Friday but my issue is still unresolved & has them scratching their heads.
We have tried 2 x new brake light switches & still have the PSM/ABS warning light.

The fault codes are 0571 & 4340.
They are still trying to resolve this for me, & I'm taking the car back on Thursday where we will try & change the MAF sensor. Any ideas based on these codes?

Dave S

 

[Richard_Hamilton]

Fault code 4340
Stop light switch
Diagnostic conditions
Ignition on
Possible cause of fault
♦ Short circuit to ground/B+ or open circuit
♦ Wiring/ plug connection faulty
♦ Mechanism of the stop light switch not OK
♦ Adjustment of the stop light switch not OK
♦ Pressure sensor plausibility

P0571
Stop Light Switch - Signal Implausible
Diagnosis conditions
Ignition on
Possible fault cause
♦ Stop light switch
♦ Wiring harness

I think I would be looking at the wiring, to check for a short or break. The diagnostic sheets for these fault codes show all the wiring checks. If you would like a copy, drop me an email.

 

[maxpaul]

I have the exact same problem with my 996tt has been since a remap and the lights come on when on max boost then reset by switching ignition off then restart have replaced MAF only other thing is whilst in the garage for the remap the battery went flat and they had to jump start the car.Thats when this problem started.

 

[Richard_Hamilton]

Just to draw a line under Dave's problem, he found that the trouble was caused by a dodgy aftermarket LED 3rd brake light. He had replaced the rear lights with LED versions, and the raised 3rd light was faulty.

Paul - Maybe you could get the fault codes read, which would be a starting point. The DME and PSM modules will store the codes for a certain time after the light has gone out.

 

[maxpaul]

Thanks Richard will try and find someone local to read the codes I am in hampshire must be someone local?
Great book Richard and thanks for signing my copy at the printers

 

[carrera4s]

Still having my problems with trhese warning lights abs/psm after having both front brake sensors replaced but what happens i can travel up to 25miles with no faults showing then for no reason they just flash on then when you stop and remove ignition key resets it self then go another 20miles or so then it happens again.Car is running fine sweet as a nut

 

[Richard_Hamilton]

I doubt the problem would be the brake wear sensors, if that's what was replaced.

Do you know what the fault code(s) were?

 

[carrera4s]

I understand it was the abs sensors that were replaced

 

[Richard_Hamilton]

That makes more sense. If the indy went by the fault codes to make that diagnosis, then it could be the wiring harness to the ABS sensor(s). Porsche make a 'repair kit' for this loom, so I suspect it is a common issue.

If you had the codes, I could look them up for you, just to confirm.