Multiple errors after replacing PCM head unit
Discussion
Hello everyone I have a Porsche Cayenne Turbo S 2004. Recently I decided to replace the standard PCM head unit, With a new pioneer head unit. Well after installing the new head unit and 14 channel amplifier to feed my speakers.
My car started to give me fault warning indictors. Brake Priority warning, 4 wheel drive warning, ABS control warning.
has anyone had this experience and can recommend a fix. Took it to my Porsche service center and they told me that all they can do is re-install the old head unit to clear the faults. I said if you do that when I re-install the new head unit will the faults persist. The said they do not know and could not help.
How to clear these fake fault warnings? HELP
My car started to give me fault warning indictors. Brake Priority warning, 4 wheel drive warning, ABS control warning.
has anyone had this experience and can recommend a fix. Took it to my Porsche service center and they told me that all they can do is re-install the old head unit to clear the faults. I said if you do that when I re-install the new head unit will the faults persist. The said they do not know and could not help.
How to clear these fake fault warnings? HELP
Congratulations on replacing the PCM; it really was a crock.
Your messages are coming from things that believe they've been disconnected - which in fact they have.
It's quite likely you can resolve some of them by ensuring you've closed the loop on the MOST fibre optic cable you disconnected from the back of the PCM. This will run from to the previous amp (say if you had Bose) and possibly any CD changer you have fitted, but certainly to the control unit that delivers info on the dash.
You're likely to need some different connectors to do this, but some of the kit can feasibly be coded out, such as phone modules etc.
Your messages are coming from things that believe they've been disconnected - which in fact they have.
It's quite likely you can resolve some of them by ensuring you've closed the loop on the MOST fibre optic cable you disconnected from the back of the PCM. This will run from to the previous amp (say if you had Bose) and possibly any CD changer you have fitted, but certainly to the control unit that delivers info on the dash.
You're likely to need some different connectors to do this, but some of the kit can feasibly be coded out, such as phone modules etc.
You'll need something like this to close the loop:
MOST Optic Fiber Break Cable Connector
The connector from the back of the PCM and possibly the Bose amp (if you have one) will look like this:
PCM connector
so you will need to remove this (they normally have push-out blue locking pins) and use the end-to-end connector above to complete the loop.
If you have a break elsewhere (do you have a Bose amp) you'll need to deal with that as well - there are shortcuts to reduce the connectors.
This gives you the idea, but you'll need to identify everything you've disconnected before you can attempt to make the errors go away.
MOST Optic Fiber Break Cable Connector
The connector from the back of the PCM and possibly the Bose amp (if you have one) will look like this:
PCM connector
so you will need to remove this (they normally have push-out blue locking pins) and use the end-to-end connector above to complete the loop.
If you have a break elsewhere (do you have a Bose amp) you'll need to deal with that as well - there are shortcuts to reduce the connectors.
This gives you the idea, but you'll need to identify everything you've disconnected before you can attempt to make the errors go away.
Pope said:
MOST System loop will not affect AWD / PSM etc; it is only infotainment.
Either the head unit isn't suited to CAN - and is powering or earthing the CAN HIGH and or LOW wires, or the issues are coincidental - any water in the car?? Check under carpets; in front bulkhead etc
I don't believe in coincidences with in-car electrics, if you change something and something else fails it's not a coincidenceEither the head unit isn't suited to CAN - and is powering or earthing the CAN HIGH and or LOW wires, or the issues are coincidental - any water in the car?? Check under carpets; in front bulkhead etc
Have you driven the car any distance, often these faults come up just by disconnecting the battery and clear when you drive it, the PSM does this in 9X7 cars and then resets itself after driving a few hundred metres
The MOST ring should not affect vehicle function as it is only media but you need to check very carefully that the CAN bus wires are not shorted, reversed or similar as per the above post
Have you added any CANbus interface ie a steering wheel remote adapter box. If so I would disconnect this and see if it helps
Close the MOST ring though behind the old PCM
Where are you in the UK. There are a multitude of car audio installation places that know these cars and will be able to sort it inexpensively if you can't
I would not go to an OPC for this (or anything else in fact), absolutely the worst place you could go
Thanks for all the great information. Been helpful. I actually based in Jakarta with the UK embassy, It seems that no one knows about MOST and the Easyget Fiber MOST Optical Optic Loop Bypass. Are not available here. It is amazing.
Took the car to Porsche big mistake they said they would have to replace the wiring harness and could only re-install the original amp and PCM head unit and its going to coat me 1200 pounds. What a crock.
I am kind of stuck between a rock and a hard place. Drive the car with the errors even the speed meter is not working. or pay the money and put back the old crapy system. Not to forget the cost of buying the new system that was just in stalled which was close to 1700 pounds. I need to get my hands on Easyget Fiber MOST Optical Optic Loop Bypass any suggestions.
HELP
Took the car to Porsche big mistake they said they would have to replace the wiring harness and could only re-install the original amp and PCM head unit and its going to coat me 1200 pounds. What a crock.
I am kind of stuck between a rock and a hard place. Drive the car with the errors even the speed meter is not working. or pay the money and put back the old crapy system. Not to forget the cost of buying the new system that was just in stalled which was close to 1700 pounds. I need to get my hands on Easyget Fiber MOST Optical Optic Loop Bypass any suggestions.
HELP
5636783 said:
Thanks for all the great information. Been helpful. I actually based in Jakarta with the UK embassy, It seems that no one knows about MOST and the Easyget Fiber MOST Optical Optic Loop Bypass. Are not available here. It is amazing.
I assume you mean you can't buy these connectors from anywhere local to you. I know it may not be helpful but can you have someone send you some from the UK or somewhere else?I would guess that many of your errors will go away once you've been able to complete the MOST (fibre) link - including the speed readout and other info in the head cluster,
As for the CANbus errors, it all depends on what's been done with the audio installation - whether the CANbus wires have merely been disconnected altogether or re-connected to something incorrectly. Many third party units won't be CANbus -compatible but did you do it yourself or get it fitted for you?
Is it therefore possible to check CANbus is currently connected because this is where your problem lies - especially because you're getting ABS and other errors.
I had the head unit installed professionally here in Jakarta. Well I would not use the word professional. They sucked and have no Idea. I just ordered the MOST fibre optic by pass two. One to terminate at the head unit and one to terminate at the AMP. Both female connectors hope they are the correct ones. CAM bus problems still not sure how to fix this. I assume when I install the MOST bypass that some of the errors will disappear? And speed meter and ABS will be ok ?? Any I ideas? Thanks for the feedback Darrel
CAN bus is a data transfer network; 2 wire based using copper wires generally 'twisted pair'; the PCM uses the Infotainment CAN network to control the ON/OFF (simulating ignition switching) and passing head unit data to the Instrument Cluster.
MOST bus is a data transfer network; optic cable based, components pass information onto a 'ring' - separately to, but in conjunction with, the CAN network.
The Infotainment CAN is two connections in the PCM connector (CAN High and CAN Low) the headunit will need to be compatible.
If you are technically minded; remove the head unit and disconnect it - if the affected systems 'heal' then you have your choice.
CAN is very robust - components can lose communication through open circuit or short circuits to +ve/-ve or mutually - once the issue is resolved comms can resume.
The original Amp is located in the right rear (RHD); the original wiring has a similar signal wire 'wake-up' that could also be a source of issues but I reckon the head unit is favourite
MOST bus is a data transfer network; optic cable based, components pass information onto a 'ring' - separately to, but in conjunction with, the CAN network.
The Infotainment CAN is two connections in the PCM connector (CAN High and CAN Low) the headunit will need to be compatible.
If you are technically minded; remove the head unit and disconnect it - if the affected systems 'heal' then you have your choice.
CAN is very robust - components can lose communication through open circuit or short circuits to +ve/-ve or mutually - once the issue is resolved comms can resume.
The original Amp is located in the right rear (RHD); the original wiring has a similar signal wire 'wake-up' that could also be a source of issues but I reckon the head unit is favourite
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