pcm not working

[scott_fx]

Hello,

i have been having electrical issues with my 03 CS. The other day i started the car and the nav/radio wouldn't turn on. no error or any information on the instrument panel display. I also have the 'check hitch' error and "check right cornering light" message. I have a dual battery setup and when i checked the voltage of my primary battery, i was getting low voltage reading. I replaced the battery but still have the errors as well as the nav/radio wont turn on. I also did the 'reset' trick found on the forums (Unlock the car and enter, close the door. Insert key but do not turn. Wait 30 seconds. Remove key, lock car unlock and test.) and had no luck with that. I also checked every fuse with my dmm. all is good there too. I'm not sure what my next step should be to diagnose the issue. could it just be as simple as needing to replace the pcm?

thanks in advance,

scott

Edited January 24, 2011 by scott_fx

[mudman2]

When you say you replaced the primary battery you did mean the one under the seat right ?

[scott_fx]

When you say you replaced the primary battery you did mean the one under the seat right ?

yup

[Richard Hamilton]

If it is a 2003 it must be PCM2.0. You can do a system reset by pressing the 1, 4, & 8 buttons at the same time. Not sure it would work if it isn't switched on though............

Edited January 24, 2011 by Richard Hamilton

[scott_fx]

If it is a 2003 it must be PCM2.0. You can do a system reset by pressing the 1, 4, & 8 buttons at the same time. Not sure it would work if it isn't switched on though............

yeah, the unit wont even turn on. but i'll give it a try

[odix]

What error codes are you getting? Also, how old is the battery you did not replace?

[scott_fx]

What error codes are you getting? Also, how old is the battery you did not replace?

there wasn't any warning light so i didnt think there would be a code. (I only have an obd-ii scan tool. will this be able to read a non emissions related code?)

the battery i did not replace is the rear aux battery (under the bose subwoofer) i'm not sure about the age of that battery.

the battery i did replace was located under the drivers seat. i am not sure about the age. it looked like it was an oem type of battery though. it could be the one that came with the car.

(thanks everyone for helping too)

Edited January 24, 2011 by scott_fx

[RFM]

A simple scanner can read no other codes than emission related codes. Since the unit wont turn on, i would check the fuse on the rear (back side) of the unit too.

[scott_fx]

ugh. i was hoping to not rip apart my dash. I may have to take it to the dealer to diagnose.

[odix]

Removing your PCM is not as bad as you think. Search the forums and you'll see the removal details. And the removal tools are not too expensive.

Also, even though your second battery may not be the cause of the issues you are dealing with you might consider replacing it to rule it out. It sounds like it's time to replace it anyway. The two batteries have, as noted by others who know a lot, distinct roles for the vehicle, but they are in the same overall super-set loop and a severly compromised battery may impact electrical component operation.

Also plug in a CTEK overnight and leave it in -- then with the engine off but the key in and turned on try the PCM and all the reset options.

[scott_fx]

Removing your PCM is not as bad as you think. Search the forums and you'll see the removal details. And the removal tools are not too expensive.

Also, even though your second battery may not be the cause of the issues you are dealing with you might consider replacing it to rule it out. It sounds like it's time to replace it anyway. The two batteries have, as noted by others who know a lot, distinct roles for the vehicle, but they are in the same overall super-set loop and a severly compromised battery may impact electrical component operation.

Also plug in a CTEK overnight and leave it in -- then with the engine off but the key in and turned on try the PCM and all the reset options.

well that's promising. I'll do some searches. I've done stereo installs before, i just wasn't sure i wanted to open that can of worms in my cayenne.

I'll also replace the spare battery this weekend.

is there a benefit of using a ctek (besides just charging) if im going to replace the other battery too, i wouldn't need to use the ctek unless it does something besides charging.

[scott_fx]

im trying to find the pcm removal instructions but i can't find them on here. i may be searching incorrectly. could anyone help me with a link?

[odix]

Mudman2 (a very savvy contributing member here on Renntech.org) has it detailed.

See pic.

The URL is: http://gallery.rennlist.com/cayennegallery/Adding-mObridge-Unit-to-PCM

The CTEK is a charger but once plugged-in (and only while it's plugged-in) it should offset battery-based power imbalances and function, in some ways, as a fully charged battery. When I first bought my Cayenne ('04 S) I sat in the vehicle for hours, engine off, ignition on, CTEK plugged in so I could learn about every detail without draining the battery or idling the engine. All the PCM settings, preferences, TPMS, seat settings, etc, etc, etc. Basically I read the entire manual siting in the car.

[scott_fx]

wow. after having to remove the front bolts of the seat rails to change the battery, i had no idea that pulling out the pcm would be so simple.

thanks for all your help. i'll report back with my results.

[scott_fx]

i removed the pcm and the fuse was good. also brought the aux battery in to get tested and it was at 100%.

im at a loss. any other ideas?

Edited January 31, 2011 by scott_fx

[odix]

That's a drag -- the upside is you have ruled a lot of issues out. It may be time to have Porsche-specific codes puled.

[scott_fx]

That's a drag -- the upside is you have ruled a lot of issues out. It may be time to have Porsche-specific codes puled.

i'll go ahead and set up an appointment. I have been nervous about going to the dealership, looks like i have no choice with this.

thanks again for your help

[odix]

Depending on how long you plan on keeping your vehicle you may want to consider purchasing a Durametic code reader. http://www.durametric.com/

It provides true Porsche-specific codes.

The Enthusiast Package is $287

[scott_fx]

Depending on how long you plan on keeping your vehicle you may want to consider purchasing a Durametic code reader. http://www.durametric.com/

It provides true Porsche-specific codes.

The Enthusiast Package is $287

thanks for the suggestion. im weighing my options right now. im considering selling my cs for either a newer cs, an similar year turbo or maybe a range rover. if i decide to go with the latter, the durametic would have a limited value to me. hmmm

[Loren]

If you really don't like high service costs then you do not want a Range Rover.

[scott_fx]

If you really don't like high service costs then you do not want a Range Rover.

does anyone like high service costs? :D The only thing that worries me about taking it to the dealer is getting raked over the coals.

i heard the 06+'s were supposed to be better (quality/reliability wise). Sadly i only have two options since my truck is also my tow rig and; living in LA, i can't really get a big truck. I also have a dog that comes with us on long wakeboarding weekends and the back is a little cramped in the cayenne. only issue i have with this suv. (wow... im basing my choice on my dog.... i need a g/f)

[scott_fx]

I finally had a chance to bring it to the dealer. and the pcm is in fact doa. the check trailer hitch warning light was resolved and they said it probably happened because my battery was dead. the right cornering light; was in fact, just burnt out.

[j3w]

Mudman2 (a very savvy contributing member here on Renntech.org) has it detailed.

See pic.

The URL is: http://gallery.rennlist.com/cayennegallery/Adding-mObridge-Unit-to-PCM

The CTEK is a charger but once plugged-in (and only while it's plugged-in) it should offset battery-based power imbalances and function, in some ways, as a fully charged battery. When I first bought my Cayenne ('04 S) I sat in the vehicle for hours, engine off, ignition on, CTEK plugged in so I could learn about every detail without draining the battery or idling the engine. All the PCM settings, preferences, TPMS, seat settings, etc, etc, etc. Basically I read the entire manual siting in the car.

Thanks for this! Adding an iPod FM interface this weekend...

Edited July 19, 2011 by j3w