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Discussion Starter · #1 ·
has anyone got any info /diagrams of hkw the suspension and its control systems work?

i have a very odd fault that i/we are struggling to solve. id like to get a better understanding of how it all works.

the fault is this incase anyone can help:-

on start up you get "PCC DEGRADED" suspension is locked in hard mode.

if you switch on and off its the same untill you have driven for aprox 20 mins. then a restart will cure it and its fine.

untill you switch the car off for long enough for the electronics to gonto sleep and then it starts over again.

the fault code is for o/s/f rebound valve open circuit.

the strut has been replaced and the wiring has been checked back to the ecu all good, it also had the ecu reflashed with the latest software but the fault remains the same.
 

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Discussion Starter · #3 ·
i had considered the APMU but as far as i know the rebound valve is on the shocker?

but this is why id like to see some documents to see what is located where and how its wired up?

is there a specific valve in there that the ecu could be calling the rebound valve?
 

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Discussion Starter · #5 ·
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these were the original fault codes. the rebound valve one will not clear. the others do.
 

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Discussion Starter · #9 ·
quick update on this. the accumulators have been replaced and just my luck exactly the same.

now being told that the next/only thing left is the pccu its self?

problem is its on indefinite back order. can a used one be reprogrammed to work with my car?
 
2012 MP4-12C
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quick update on this. the accumulators have been replaced and just my luck exactly the same.

now being told that the next/only thing left is the pccu its self?

problem is its on indefinite back order. can a used one be reprogrammed to work with my car?
I have my doubts on it being the PCCU, from everything I've seen posted I believe it to be the APMU as that is the actual valve body that controls things. A used PCCU can be VIN programmed to work on your car though.
 

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Discussion Starter · #12 ·
so my understanding is the valve that the fault code refers to is on the strut its self??

would you have a wiring diagram of the suspention system so i can do some checking or pin data fornthe ampu/ pccu so i can check for any faults that way
 
2012 MP4-12C
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so my understanding is the valve that the fault code refers to is on the strut its self??

would you have a wiring diagram of the suspention system so i can do some checking or pin data fornthe ampu/ pccu so i can check for any faults that way
What makes you think it's the strut itself? The code specifically says APMU leak in it.
 

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Discussion Starter · #14 ·
the other code says damper control front right rebound open circuit. this is the code that originally pointed to the shocker rebound valve on the strut?
presumably the ampu is detecting the leak past the rebound valve?

is it possible that this actually refers to a valve in the ampu and not the strut?
 
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the other code says damper control front right rebound open circuit. this is the code that originally pointed to the shocker rebound valve on the strut?
presumably the ampu is detecting the leak past the rebound valve?

is it possible that this actually refers to a valve in the ampu and not the strut?
Circuits aren't necessarily electrical. The APMU IS the valving that happens in cross flow, meaning the up and down, not the dampening. I feel pretty confident it's the APMU.
 

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Discussion Starter · #16 ·
today ive done a bit more testing. not that ive found anything.

tested the resistance of both front rebound valves both the same at 4.0/ 4.5ohms

tested the resistance at plug (so the resistance of the wiring and ecu) both the same 139 and 138.5 ohms.

that would say that theres no problems with the valve wiring or ecu to me?

so as yet i can not explain this open circuit code that it constantly gets.

im beginning to think that this is more something to do with the Cambus system than an actual physical fault. the way that the fault clears after a while but reappears every time the cars systems go fully to sleep.

its like it looks for a signal from an initial self test and its not there. after a while it ignores it and works.

there is so little information out there about how the system works its almost impossible to tell what to look for.

above you can see the fault for "powertrain can bus off"

if the pccu was fully off the can bus system i would expect a lot more problems than im having.

im not sure what if anything else i can test at this point.

logically its got to be either the PCCU or the APMU

my specialist think pccu and i know EMF you think ampu. can anyone think of a way to test or rule out either? otherwise im back swoping out very expensive parts and hoping
 

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Not sure if they are the same issues , message in my car "PCC degredation" brand new accumulators , turn out there was leak front suspension
they replaced 2 hoses ..
 

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You need someone with actual McLaren Diagnostic tool to scan the car. The McLaren diagnostic tool will point directly to the faulty sensor, circuit, or issue to work on.

AND... It also has guided functions (for many issues - not every issue) that guides the technician exactly where to test the wiring and functions of the system.

Kevin
Supercar Garage - The McLaren Specialist
770-284-0172

Kennesaw GA
* Home of the flying McMedics... The only mobile McLaren Specialist! -We come to you!
 
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