Central locking behaving strangely

[Willow5]

Hi @Loren, no not as yet. I assumed this was a simple wiring/grounding issue given the following conditions are true:

 

1) the rear tailgate switch appears to be working fine

2) the fuel cap release switch from the drivers door is working fine which is also routed into the drivers control unit

3) there is voltage on the pins foing into the tailgate release switch

4) the switch itself is ok

 

Right now, I have 3 unresolved issues:

 

1) starter motor is sluggish and never starts on first turn. Always takes at least 2 turns to fire up

2) rear tailgate release button on the drivers door and remote keyfob are not working (although with a long keypress on the keyfob, the rear tailgate glass panel does release).

3) the alarm doesn't sound, only the hazard lights illuminate

 

Would a PIWIS or Durametric scan assist with these issues?

 

Please note that I managed to clear up 1 issue with some cleaning of the ground points which was the original issue I had with the central locking not locking the tailgate, this now appears to work correctly.

Edited April 2, 2020 by Willow5

[Loren]

It may help pinpoint where issues are.

[Willow5]

Hi @Loren, forgive me but what type of things could such a scan pick up? I am of the opinion (rightly or wrongly) that this is a hardware issue like a broken wire or ground issue, what do you think?

[JFP in PA]

17 minutes ago, Willow5 said:

Hi @Loren, forgive me but what type of things could such a scan pick up? I am of the opinion (rightly or wrongly) that this is a hardware issue like a broken wire or ground issue, what do you think?

 

It could pinpoint where the fault is in the system, dramatically reducing diagnostic time.

[Willow5]

Hi @JFP in PA and @Loren, to be honest I am not sure I will get hold of such a scanning device anytime soon given the lockdown.

 

In absence of this, can I get an idea of what sorts of issues could cause the faults I am observing. Could this be a driver door control unit issue for example?

Edited April 2, 2020 by Willow5

[JFP in PA]

Yes, or it could be a commination's fault, an "implausible" signal in the system from sensor, a module that has lost its programing, etc.  The question is which one and what fault, and where is it, which only a scan would answer.  You could spend a lot of time chasing your tail not knowing where to start.

 

[Willow5]

Hi @JFP in PA, if I were to simply replace the driver door control unit, could this be done without any reprogramming,  for example, is it a simple plug and play swap ? I could source one quite easily from ebay.......are these prone to going bad?

Edited April 2, 2020 by Willow5

[JFP in PA]

2 minutes ago, Willow5 said:

Hi @JFP in PA, if I were to simply replace the driver door control unit, could this be done without any reprogramming,  for example, is it a simple plug and play swap ? I could source one quite easily from ebay.......are these prone to going bad?

 

As a general rule, no, module replacements typically require either programming or activation steps requiring a PIWIS.

[Willow5]

@JFP in PA, ok then are there any further troubleshooting techniques I could do in absence of a PIWIS or reader? I read the voltage at the tailgate switch pins in the drivers door card and they check out ok but I have 4 wires and the diagrams I have seen only show 2...slightly confused by this

[JFP in PA]

1 minute ago, Willow5 said:

@JFP in PA, ok then are there any further troubleshooting techniques I could do in absence of a PIWIS or reader? I read the voltage at the tailgate switch pins in the drivers door card and they check out ok but I have 4 wires and the diagrams I have seen only show 2...slightly confused by this

 

Not really, there only so much a digital multimeter can tell you about systems with control modules in them; they cannot see the module programming, state of activity, or read the signals they send out to see if they are correct.  You are limited to voltage, continuity, and amperage; which may not answer the question.  This is the problem when you have digital "thinking" modules in a electrical control circuit; you need to know what the module is, or isn't thinking, which requires a more sophisticated tool.

[Willow5]

@JFP in PA, I understand thanks. Are there any other troubleshooting guides online that I could take a look at ? My troubleshooting logic is this:

 

There is clearly a connection between the drivers door control unit and the rear part of the car given that I can open the fuel cap. The control unit clearly has access to the CAN bus in order for this part to function. The tailgate itself and all the motors are fine given that I can open all rear doors fine with the buttons on the rear. The tailgate switch is also working fine.

 

My only other thought was that there could be a broken wire somewhere....I read a few times that wires occassionally get torn between the door rubber boot and the body.  I have yet to take the rubber boot off to inspect further. Could this be an issue?

[JFP in PA]

8 minutes ago, Willow5 said:

@JFP in PA, I understand thanks. Are there any other troubleshooting guides online that I could take a look at ? My troubleshooting logic is this:

 

There is clearly a connection between the drivers door control unit and the rear part of the car given that I can open the fuel cap. The control unit clearly has access to the CAN bus in order for this part to function. The tailgate itself and all the motors are fine given that I can open all rear doors fine with the buttons on the rear. The tailgate switch is also working fine.

 

My only other thought was that there could be a broken wire somewhere....I read a few times that wires occassionally get torn between the door rubber boot and the body.  I have yet to take the rubber boot off to inspect further. Could this be an issue?

 

It is worth a look.

[Willow5]

Hi there. Before I go and get the scan done and spend more time troubleshooting, please can someone kindly confirm the operation of the tailgate switch in the drivers door.

 

I read on a touareg forum that the function of the switch is as follows:

 

"On mine (an '04) that switch only allows you to open the hatch after you have locked the car. ie, flip the switch, get out of the car and lock it, go to the rear and open the hatch using the switch above the license plate, retrieve your packages, close the hatch and the car re lockets itself. The feature times out after about a minute. In other words, the switch allows the hatch to open for a period of time after the car is locked. It does not open the hatch directly."

 

Is this the correct function of the switch when working? If so, I have been operating it incorrectly.....

[Willow5]

Doesn't anyone here know the function of the door tailgate switch??

 

I came across this article on another forum which describes exactly what I am encountering. Please can someone kindly confirm this is the operation of the tailgate switch and keyfob?

 

Tail Gate Wont Open From Key Fob or Drivers Door - Rennlist - Porsche Discussion Forums

RENNLIST.COM

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Cayenne 955-957 2003-2010 - Tail Gate Wont Open From Key Fob or Drivers Door - Morning All, I have just purchased a...

 

Edited April 7, 2020 by Willow5