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The PCM 2.0 unit in my 2003 Cayenne has been intermittently playing up recently, powering up on some occasions and not on others.

The model of the unit is BE 6635.

I have experience in the electronics industry and my curiosity got the better of me and so I pulled the unit forward from the dash and opened the lid for a visual inspection. I reasoned that maybe I have a suspect dry solder joint etc.

As fate would have it the unit worked perfectly when it was naked in front of me.

There was an orange LED on the main board which was illuminated when the unit was on and I could see the red fiber optic light flashing on and off at the back of the fiber plug. The display was working along with all the other functions.

On another occasion when the unit was not working, I noticed that the orange led was not illuminated on the main board.

Power was still available as the nav cd would spin up for about 30 secs and then stop.

When the unit would recover from its non working state, the OBC info such as the average fuel used, distance traveled, time since reset info, would all be reset to zero.

I suspect the orange led not illuminating is a clue as to what is wrong with the PCM 2 unit.

I tried getting circuit diagrams and service literature from Porsche and Harman/Becker with no luck as the item is proprietary blah,blah,blah.

They will sell me a new or exchange unit for a lot of money since I am out of warranty.

I have attached a picture with the orange led location (yellow arrow) for reference.

Does anyone have any info they can share on this? :help:

Thanks.

post-36777-1245682533_thumb.jpg

Edited by bigbuzuki

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Maybe it is the orange lead. I would call sunset imports

and see if you can order the lead. It also could be the orange lead is twisting on

the clamp when you slide it back in. You might be able to use a short sliced tube with a little

electrical tape to keep it square.

Paul

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The car side of the wiring is ok as I have had the unit out of the car and on a bench with a power supply connected to it and have witnessed the same fault.

On the bench the unit powered up perfectly with active display and was able to select different modes. Then on another occasion the unit shows the same fault, ie blank display, the cd spins up for about 30 secs and stops, and the orange light emitting diode (led) is not on.

The main board is double sided and a little complex to visually trace back the power circuit. This is where the circuit diagrams would be handy.

I don't believe the unit is losing all its power because with the fault present, the cd spins up ok, the fibre optic led flashes on the back of the unit and the display illuminates with the backlight although no picture or letters are present.

I have had the unit on a bench with a power supply connected and with the fault present it still draws about 500mA of current.

Edited by bigbuzuki

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The car side of the wiring is ok as I have had the unit out of the car and on a bench with a power supply connected to it and have witnessed the same fault.

On the bench the unit powered up perfectly with active display and was able to select different modes. Then on another occasion the unit shows the same fault, ie blank display, the cd spins up for about 30 secs and stops, and the orange light emitting diode (led) is not on.

The main board is double sided and a little complex to visually trace back the power circuit. This is where the circuit diagrams would be handy.

I don't believe the unit is losing all its power because with the fault present, the cd spins up ok, the fibre optic led flashes on the back of the unit and the display illuminates with the backlight although no picture or letters are present.

I have had the unit on a bench with a power supply connected and with the fault present it still draws about 500mA of current.

It is very likely a dry solder joint somewhere, however, trying to spot it on a PCB with surface mount components is gonna be near impossible. I recommend reflowing the board with Heat Gun, it will definately solve the problem. These units can get quite hot and suffer if any soldering is sub-standard.

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Perhaps a stupid question, but have you already checked the fuse connection ? (fuse on the PCM unit)

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Had some luck with rectifying the fault on the PCM.

With the defect active I began taking some DC voltage measurements from the test port connector on the board.

I noticed that the DC voltages were not stable and kept fluctuating.

I began flexing the PC board gently and noticed that the voltages became stable when the board was pressed around the ST10F269-T6 chip.

I reheated the solder on all the power pins of the same chip and WELLA, the orange LED illuminated and all is well.

Special thanks to TwinCharger for the advice of reflowing the solder.

The ST10F269-T6 chip is marked with a red A and the power pins are marked in yellow. The test port connector is at position B.

Unit has been reinstalled in the vehicle and has operated perfectly since the repair.

:cheers:

post-36777-1246117404_thumb.jpg

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Had some luck with rectifying the fault on the PCM.

With the defect active I began taking some DC voltage measurements from the test port connector on the board.

I noticed that the DC voltages were not stable and kept fluctuating.

I began flexing the PC board gently and noticed that the voltages became stable when the board was pressed around the ST10F269-T6 chip.

I reheated the solder on all the power pins of the same chip and WELLA, the orange LED illuminated and all is well.

Special thanks to TwinCharger for the advice of reflowing the solder.

The ST10F269-T6 chip is marked with a red A and the power pins are marked in yellow. The test port connector is at position B.

Unit has been reinstalled in the vehicle and has operated perfectly since the repair.

:cheers:

post-36777-1246117404_thumb.jpg

Well done - glad I have been of help!

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Hello.. I am trying to access to the circuit board of my 2005 Cayenne PCM 2.1 to install the xcarlink video interface but I have a hard time open the case because I don't want to force it and break something. Since I see you opened your pcm board, can you show me how to open the case to access the circuit board ..

Thanks

Ken

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Hello.. I am trying to access to the circuit board of my 2005 Cayenne PCM 2.1 to install the xcarlink video interface but I have a hard time open the case because I don't want to force it and break something. Since I see you opened your pcm board, can you show me how to open the case to access the circuit board ..

Thanks

Ken

This is for a PCM 2.0 cd based navigation, I do not know if the 2.1 PCM is the same.

1. Remove the 2 small torx screws on the top cover, forward edge.

2. There are 2 tabs interlocked, one on each side, on the bottom edge of the top cover towards the front, you can lever a screwdriver at those points with a twisting motion to seperate the top cover from the bottom cover.

3. The cd drive mechanism is physically mounted on the underside of the top cover so carefully lift the top cover and disconnect the cd connector from the main board.

Hope this helps.

Edited by bigbuzuki

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I second SA321's comment -- indeed this is seriously impressive. Put it another way: you sir are a stud.

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So, if anyone is interested:

I had the same problem with my PCM from my Cayenne S - 2009.

It had the same simptoms , changed the battery, but no effect. So i opened it up. In most part the base plate , it was the same. But the position A labeled chip is not the same. It had different type of soldering. So i could not reheat anything.

I just took everything apart, and cleand it with contact spray. Blow it with compressed air, and nothing more.

Already was feeling bad for the upcoming result, that nothing will change.

So i started to out everything toghether back in place and installed in the car.

it showed me the Porsche logo screen when power was connected, and then off.

So, i pressed the power button, and guess what ?? It started right away. I could not belive my eyes. Then i shuted down the sistem. and on again. and again, started with no delay, no other problem. and again on, and off, on and off.

The result was amazing. The PCM was working perfectly, and this, without putting the ignition.

So, it seems, for the moment, that a good cleanup was enough.

Hope it won't break down again.

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When you say you reheated the solder around the chip, how exactly did you do that? I'm curious for future electronic repair endeavors that I may face.

Awesome job!

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My 08 Cayenne Turbo's PCM has different PCB from Bigbuzuki's. It did not want to switch on. Then, I remove it from my Cayenne and check the PCB. Unfortunately, my ST10F269-T6 chip is different from above. see below photos. Can anyone help to rectify this problem ?.

post-88658-0-52354500-1380720844_thumb.j

Edited by IBEQUIP

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My 08 Cayenne Turbo's PCM switch on by itself while I stuck at traffic jam. Then, "Engine Off Operation only possible for short time" appear on the PCM eventhough my engine is running. after few minutes PCM turn off by itself. this cycle happen for few times. after that, it did not happen again eventhough i drove my cayenne for about 4 hours. Up to now, my PCM is still dead. Is this problem caused by weak battery ?. I also plug my durametric cable two days later and the green light is not on.

post-88658-0-45183900-1381067601_thumb.j

Edited by IBEQUIP

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put the new battery Bosch S5585B few days ago but the PCM will not switch on too. Planning to send to Porsche Authorised dealer this week. any other advise ?.

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My PCM 2.1 cycles on and off for about 20-30 minutes and then it operates perfectly. If i stick a small ceramic heater in the car for 20 minutes before driving, it also works A okay.

I have field stripped the PCM at least 2x now and at least know how to do that pretty ez.

I have concluded that it is a cold solder joint somewhere and will try inspect the large square chip as noted by the OP but, mine is soldered via the bottom of the board. All these looked okay last sunday when I took a cursory look.

It's all sort of a crap shoot, but summer may be here sometime and the unit will probably work fine then. Failing all this, I will send it off for repair to either Becker or a place that "may" do this sort of thing called Module Masters.

Too bad there is no available schematic for this.

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