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Hoping someone can help with this!

 

Have an issue with PDC at the rear of my 2001 E39 where if you turn the ignition to position 2 (dash lights on) and turn on the PDC and walk up to each they work fine. If I connect the laptop and view the output of all the sensors they can be seen to be working OK. 

 

However, if I start the car the sensors then go mental and start beeping away and the laptop shows they think they're detecting something - 

 

No error codes recorded

 

Actions so far:

I have replaced all the rear parking sensors

All rear sensors click away fine

I have replaced the PDC unit

I have cleaned all the connections

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I have something similar with one of mines, it intermittently detects when nothing is there (only with PDC in use) 

This is a new sensor, last one did the same, it's one of the two middle painted sensors, I thought it was the paint but it's intermittent so not sure at all. 

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As soon as i start the engine the sensors detect something - the bars showing the distance on each sensor show it randomly detecting something i.e. they dont detect something to the same distance, the bars go up and down super fast and randomly.

 

What's cracking me up is that it works bang on with the ignition on but as soon as u turn the key it goes mental. Swapping sensors has no effect

 

i'm not sure what else i can do now!

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Might be some form of electrical fault that activates the system somehow once you turn the key and thinks it is detected an object.

 

Chaffed wire?  That get a signal from another "ignition on" source that provides a false feed so the system thinks it has detected something?

 

Would be a nightmare to trace though.  

 

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There is a loom / harness between the PDC unit and the 4 rear sensors, maybe worth checking that for any shorts, possibly replacing it 

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ah ok, thanks for the advice - i'm in Northampton - i some time off in a few weeks so i'll probly pull the bumper off then and check it out - soooo annoying!

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On 7/31/2016 at 9:58 AM, jonwil560115 said:

i've just bought a rear PDC wiring loom from Ebay so i'll just fit this during my time off and hopefully it'll be a winner :)


Hi! Reviving an old thread here! I see this was from a while ago now but I am having the exact same symptoms as you were describing with my E39 and just wondered if you found replacing the rear wiring loom fixed the issue? Cheers!

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