Rear park assist

[angusc]

I have been struggling all day to get my rear park assist working. The front works ok but the rear would always show immediately the red lights. On the PIWIS or Durametric analyser it showed the rear sensors were short circuit to +B.

The rear bumper looks as though it had been repainted as well as the sensors, so I removed one rear sensor and plugged it in to the front harness. This resulted in the front system giving red light and not working.

So next I removed the rear sensors and buffed off the paint and re fitted. Now when putting the car in reverse it momentarily shows the green lights for about 2 seconds before turning red. Also now PIWIS does not show any fault codes for the sensors.....so it looks like the sensors are now working ok.

But without any fault codes I'm a bit lost for what to try next.

Anyone have any ideas?

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[lewisweller]

17 hours ago, angusc said:

 

I have been struggling all day to get my rear park assist working. The front works ok but the rear would always show immediately the red lights. On the PIWIS or Durametric analyser it showed the rear sensors were short circuit to +B.

The rear bumper looks as though it had been repainted as well as the sensors, so I removed one rear sensor and plugged it in to the front harness. This resulted in the front system giving red light and not working.

So next I removed the rear sensors and buffed off the paint and re fitted. Now when putting the car in reverse it momentarily shows the green lights for about 2 seconds before turning red. Also now PIWIS does not show any fault codes for the sensors.....so it looks like the sensors are now working ok.

But without any fault codes I'm a bit lost for what to try next.

Anyone have any ideas?

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Get a really quiet area and put car in reverse with ignition on engine off. Then jump in the boot, and pass your hand over each sensor, you will hear a faint click if the sensor is good. No click or very weak click normally indicates a dead or faulty sensor. 

[angusc]

Thanx I will try that now and see what happens. Is it more common for the sensors to fail rather than the module? The function test is all good for everything and since cleaning of the paint from the sensors I don't get the short to B+ error any more.

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[lewisweller]

1 hour ago, angusc said:

Thanx I will try that now and see what happens. Is it more common for the sensors to fail rather than the module? The function test is all good for everything and since cleaning of the paint from the sensors I don't get the short to B+ error any more.

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The other possible fault is the sensor is not flush with he bumper and it sees the edge and false warning happens when slow turning. My front does this which is annoying but ignorance is bliss sometimes. 

I would suggest you have intermittent or weak sensor(s). Some fail due to water ingress, after car wash or rain shower they play up I've read. 

 

Find the one with no click or a weak click and likely you found the culprit. 

[angusc]

I replaced all rear bumper sensors but still the same problems.when put in to reverse the two red segments light and a 3 second solid tone is emitted. Then tone stops and red lights stay on. Front system working ok. Does anyone have any other suggestions.....where is the rear park assist control module located and is it likely to be the fault or worrying around the rear

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[lewisweller]

17 minutes ago, angusc said:

I replaced all rear bumper sensors but still the same problems.when put in to reverse the two red segments light and a 3 second solid tone is emitted. Then tone stops and red lights stay on. Front system working ok. Does anyone have any other suggestions.....where is the rear park assist control module located and is it likely to be the fault or worrying around the rear

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Rear left side of boot.

Follow link my friend. FYI get a used module of the same year no need to reprogram plug and play if only the module is faulty. Check the wiring that runs under the boot floor for damage. 

http://rennlist.com/forums/porsche-cayenne-forum/785774-park-assist-control-module-replacement.html

 

Happy new year 

[angusc]

Thanx for that, removing the rear trim looks horrendous but a necessity to gain access. I will locate a replacement control unit first before going any further.

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[skalex]

Hi angusc,

Did you figure out if it is your module? I have the same issue, 2 reds on both sides front and rear, all sensor clicks, no fault on durametric.

I removed the module and everything look ok inside (no burn mark....)

I am not sure if I try to replace the module

[angusc]

Hi Skalex, no I have not played any more with it to test if the model is the problem. I have been away from the car for a few months so no chance to test it further.

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[skalex]

Thanks for your feedback. I will maybe just buy one and try!

[skalex]

just to follow up, I found a used module for a really good price on ebay ($35), ordered and received 2 days later.

I changed it this week end and it was a module problem, everything work now!

 

[lewisweller]

1 hour ago, skalex said:

just to follow up, I found a used module for a really good price on ebay ($35), ordered and received 2 days later.

I changed it this week end and it was a module problem, everything work now!

 

Sweet. Thanks for posting your successful Fix. 

[angusc]

Just as an update on my rear park assist issues and the eventual fix. I removed the right rear inside trim to get to the module, it's Weir involved but do able just needs time and patients then I started trouble shooting following the workshop manual. I had 4.8 voltage going out to the sensor harness connector but the rear park assist never worked. I had previously purchased all new sensors but they made no difference. I was thinking the fault was going to be that module but it just didn't add up in my mind as there was power to the sensors. So I paid more attention to the rear bumper harness and connectors. Sure enough I found that the main connector wasn't making a good contact with the bumper harness. I cleaned and scrapped the plug pins and a bit of WD 40 did the trick. I also used a small zip tie to firmly hold the plugs together. Now all working!

My original fault was that in reverse only the outer red lights on the rear PA display would light and stray on. It means there is a fault.

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