During Hard acceleration PSM, ABS and Brake Fluid lights come on.

[Balbir]

I have a 2001 911 turbo with 68,000 km. During a hard acceleration, PSM, ABS and Brake Fluid lights come on. When I restart the engine, these lights turn off but the PSM remains deactivated.

I have read lots of forums and none of them really address my situation. Some of the forums say that battery fluid shifts during a hard acceleration and can cause these lights to come on. I have changed the battery and the lights still come on.

These lights started to come on after I changed the drive belt. In order the changed the drive belt, I had to take of the air box and MAF. Some of the forums suggest that MAF sensor could be faulty. I was very careful with the MAF sensor and I didn’t drop it when I changed the drive belt. I believe if the MAF sensor is faulty, then I should get a fault code.

I don’t know if the brake fluid level senor is faulty. I don’t know how to test it. However, when I did disconnect the brake fluid sensor, the PSM and brake fluid lights came on. Then, I reconnected, both lights turned off.

If anyone has a suggestion, please reply to this post. I would greatly appreciate it!   

[jpflip]

I do not believe in battery fluid shift???? The last thing you touch before this fault came on,  that can be related to a PSM ABS message, was the MAF. I got tendency to think also your MAF is at fault. Get some CRC Maf cleaner from Canadian tire. It is good stuff and worth to give it a try, only $8.49 a bottle. Do not touch any elements only spray them and let it evaporate….

 

 

http://www.canadiantire.ca/en/pdp/mass-air-flow-sensor-cleaner-0381704p.html#.VEkkbEuJIxI

Edited October 23, 2014 by jpflip

[Ahsai]

Would be easier if you can get the car scanned by Durametric or alike to get the actual fault codes and go from there.

[JFP in PA]

I have seen this before, but on a car with an AGM battery which has no free fluid in it, so I would forget that explanation.  The key here is the drive belt, it is slipping enough to let the electrical system voltage drop, which is a common cause for ABS, PSM & other MIL lights to come on without reason.  On the one I saw, the owner purchased an aftermarket belt which was very slightly larger than the OEM, which allowed the belt to slip under load, and the voltage dropped.  The way we caught it was a road test with the Durametric connected and logging data; stand on the gas and the voltage took a nose dive, back off the gas and the voltage came back up.

[Ahsai]

^That's where experience counts :) So why the drive belt was slipping? Bad belt/tensioner?

[JFP in PA]

No, it was very slightly too long, and perhaps a little too smooth as well, so the tensioner could not hold it tight enough under load and it slipped just enough for the voltage to drop off momentarily and trip the MIL's.  Put on another new belt (OEM) and the problem went away.  The OP said his problems started after a belt change, so it is definitely worth a look as not all belts are equal.

[Ahsai]

Very interesting. Definitely not something you can get from the boring troubleshooting flow charts.

[JFP in PA]

Very interesting. Definitely not something you can get from the boring troubleshooting flow charts.

 

Which is why we put the Durametric in the car and took it for a run, sometimes you have to "catch the moment" and start asking yourself questions, like what would cause a sudden voltage drop, and if the owner had just replaced anything, like the belt.  Then the observed data ties into an active hypothesis, or in this case, how could a new belt cause the voltage to suddenly drop; which can easily happen if it slips, which was exactly what we found.  Not earth shattering, but it happens.

 

Sometimes the best answer is the simplest one.

[Silver_TT]

electrical system voltage drop, which is a common cause for ABS, PSM & other MIL lights to come on without reason

 

 

I agree with that statement.  I would check the codes as Ahsai already pointed out but I experienced something similar when my alternator was going out.  I was at very high RPMs climbing a hill and all of a sudden felt a loss of power, the ABS light came on, and the car went into limp mode.  It turns out the alternator was going out and was doing funny things...but only at certain RPM ranges, which was the bizarre thing.  At certain RPM ranges I was seeing the voltage bounce around all over the place and do weird things.  It may have also been exacerbated by the wiring harness which I replaced as well, as it happened on a 100F+ day and I noticed the car had started acting strange as soon as the ambient temp went through the roof that week.

 

I also agree about checking the drive belt.  I have seen more than one owner that reported drive belt slippage with the TT (although I personally never experienced it).

 

Also a reason not to use aftermarket parts.  Experience has taught me that the old cliché "what's cheap is expensive" is more often correct than not.

Edited October 26, 2014 by Silver_TT

[Balbir]

thanks for your suggestions.  I did put an OEM belt, Conti, but bought it from an aftermarket store.  Porsche dealer was selling for $135 and the aftermarket sold for $25 online.   I can try the OEM from Porsche and see if it fixes the problem.

[JFP in PA]

thanks for your suggestions.  I did put an OEM belt, Conti, but bought it from an aftermarket store.  Porsche dealer was selling for $135 and the aftermarket sold for $25 online.   I can try the OEM from Porsche and see if it fixes the problem.

 

Assuming the old belt was still in good shape, you could put it back on and run a test with it as well.

 

Weird belt sizing is not uncommon, we see it from time to time; some times it is just miss marked or packaged, other times the belt was definitely the wrong size..

[Balbir]

I don't have the old belt.

 

Today I did clean the MAF sensor and no change.  Today, the lights came on under a moderate acceleration on a bend when I made the rear wheels lose traction little bit.  I then restarted the car and lights went off.  However, the PSM hasn't worked ever since the lights started to coming on. Even when I restart the car and the lights turn off, I can spin the rear wheels, which means the PSM doesn't work.

 

Also, I did check the boost and it seems like working.

[JFP in PA]

I don't have the old belt.

 

Today I did clean the MAF sensor and no change.  Today, the lights came on under a moderate acceleration on a bend when I made the rear wheels lose traction little bit.  I then restarted the car and lights went off.  However, the PSM hasn't worked ever since the lights started to coming on. Even when I restart the car and the lights turn off, I can spin the rear wheels, which means the PSM doesn't work.

 

Also, I did check the boost and it seems like working.

 

Check your car's electrical output voltage an idle.

[Silver_TT]

Sounding a little more like what I described as far as a voltage gremlin (wiring harness?, etc).......however, if you just changed the belt and the problem manifested itself immediately afterward, I would be sure this isn't related because that would be a coincidence (although still possible, of course).  If you trace the voltage back, this will narrow down the potential problem.  Ahsai had a nice write-up on this in the past.  This is a known issue on the 996 and 997s and there are some updated part #s that addressed this.  You would really want to trace the voltage back at idle as JFP says to start narrowing the possibilities IMHO.  If that's what it is, it's not terribly expensive or difficult.... these cars do all sorts of funny things though when your voltage isn't 100% right.  Best luck

[Balbir]

Silver_TT, thanks for your reply. I didn't really understand exactly what you have suggested.  What is JFP and IMHO?  Would please advise you suggestion again? 

[JFP in PA]

Silver_TT, thanks for your reply. I didn't really understand exactly what you have suggested.  What is JFP and IMHO?  Would please advise you suggestion again? 

 

 

JFP is me, IMHO is "In my humble opinion".

[Silver_TT]

Yes, and just to elaborate I was saying that if your PSM still isn't working it could indicate a voltage issue.  This could be from your battery, alternator, but may more likely be from the cables that connect them all together.  I was just saying that Ahsai, another user on this forum, has written up instructions in the past on how to test this to see where you might be getting a voltage drop.  Otherwise if you don't feel comfortable doing this yourself I was just saying that a good Porsche shop should be able to diagnose this pretty quickly.

 

You can also have your battery tested very easily and this might not be a bad place to start.  A battery that's less than 100% in these cars manifests itself in weird ways sometimes.  If you suspect the alternator they can also pseudo-test the alternator in minutes as well without taking it out of the car.  JFP owns a shop so he sees more of these cars, but based on my experience it's usually one of the wiring harnesses.  And there was even a Porsche TSB (a memo released by Porsche advising customers of a potential issue or important note) regarding this and some updated part#s for cables which are less prone to this issue (I believe they are a thicker gauge).

Keep us posted and let us know what you find.

Edited October 28, 2014 by Silver_TT

[Ahsai]

This is the voltage drop test write up Silver mentioned http://www.renntech.org/forums/topic/47504-troubleshooting-low-voltage-and-charging-issues/

[Silver_TT]

Ahsai - Great idea making that separate for easier search.  Lots of folks will find that very useful as this is a pretty common issue especially for folks with the older version of the cable.

 

Balbir - Just to repeat, if you did just replace that drive belt (or anything else) immediately before this started happening I would be sure to give that a long look.

[Ahsai]

Thanks, Silver! I had problems finding it myself a few times haha

[Balbir]

Silver_TT, thanks for the reply.  Before replacing the belt, I did change the transmission (gear oil) and engine oil a week earlier and the car ran fine. I don't have low voltage light but I'll check the voltage with the meter.  Some of the forums suggested faulty battery.  I did change the battery  and it had no change on the symptoms.

[Silver_TT]

Seems weird you just replaced the belt then and this problem started.  The problem I was describing with the wiring harness is fairly common so it's not out of the question that it's completely unrelated, just seems a bit odd timing-wise if you just did the belt.  As I said, just be sure to give that a long look.  Gear and engine oil should have nothing to do with this as long as nothing was knocked loose with the wiring, etc.

 

You wouldn't have a low voltage light or anything like that in many circumstances.  The PSM light sometimes is the low voltage warning :)  Definitely need to follow that Ahsai guide to testing to see where you could potentially be seeing a voltage drop.

[vglnte1]

I have the same issue , but just abs and psm. Pretty sure it's due to a boost leak or something. I get an occasional maf code, but I've just lived with it for the past 2 years.

[Silver_TT]

Nice pic!  FYI, I don't think a boost leak is going to cause that behavior.