Parking Sensor Buzzers not buzzing

[Fraz-ktf]

Hi.
neither front nor rear Parking sensor buzzers are buzzing.  The Dash Switch blinks when I get near something though.

I've checked the previously repaired rear wash-wipe pipe in the front footwell (That was fixed together with some industrial self-bonding tape) and found that the industrial self-bonding tape (That won't even cut with a Stanley knife) has a hole blown in it and the pipe has come undone again!!!!!

Wet carpet, wet soundproofing but after removing the passenger seat, expecting to see a puddle, it is totally dry under there (I had raised the controller box anyway, by 10mm just-in -case).

I'm at a loss as to what to check next for the buzzer issue, with the control box being bone dry. (I've also moved the front buzzer previously, to under the dashboard in front of the driver - works fine there - or did ;-) )

Here's what VAGCOM has to say:
Control Module Part Number: 7M3 919 283   
  Component and/or Version: Parkingsyst. SH RDW D02
           Software Coding: 00117
            Work Shop Code: WSC 00020
2 Faults Found:
01543 - Parking Aid Warning Chime (H15)
        31-00 - Open or Short to Ground
01625 - Front Parking Aid Warning Chime (H22)
        31-00 - Open or Short to Ground

End   -----------------------------------------------------

[SilverBeast]

I'd interpret that as the writing you put in when you moved the buzzer us either shorting together or has become detached.

[Chrispb]

If the speakers are connected properly check fuses 2 & 5 if still not working have a look inside control module for corrosion.

[Fraz-ktf]

If the speakers are connected properly check fuses 2 & 5 if still not working have a look inside control module for corrosion.

checked the speakers - connected ok
Checked the fuses suggested - ok

where is the control module located and what does it look like?  - if it's the box under the passenger seat with the 3 x plugs to it, this box didn't get wet because I had raised it off the floor previously 
The wires to the front speaker go in to the loom that runs by the passenger door and without cutting the loom open to trace, I'm stumped 

[Fraz-ktf]

The plot thickens . . . 

Having found out that it is the black box under the passenger seat, I have taken out a known working one from an identical vehicle.

I get the same problem when I fit it to my "Duff" vehicle.  No sound but the parking sensor dashboard switch flashes continuously.

My control unit in the other vehicle gives the same symptoms.

Known working unit in the "Working vehicle" - the switch flashes, then becomes constantly on and detects audibly.

all the sensors on my "Duff" vehicle are clicking merrily regardless of which control unit is fitted.

I'm guessing the problem is elsewhere?  Would I need to clear fault codes for the "Test unit" to then work in my car?

any suggestions anyone coz I'm stumped!!!

[Fraz-ktf]

Cleared the codes with VAGCOM and they came back with the same codes:

2 Faults Found:
01543 - Parking Aid Warning Chime (H15)
        31-00 - Open or Short to Ground
01625 - Front Parking Aid Warning Chime (H22)
        31-00 - Open or Short to Ground

Obviously something to do with the actual chimes or wires but can't fathom what to check next 

[Mirez]

So your car's control unit in the good vehicle stops that one working but the good car's unit in your car also stops working?

Clearing the codes shouldn't make and difference because that module is classed as "non latching", ie the codes can self-reset.

Open circuit is just a technical way of saying the circuit isn't complete although its strange that its for both chimes - did you move both or just the front? I think what's especially strange here is that the front and rear sounders are on different connectors into the unit and the external wiring is therefore entirely separate. I think you might have to get the multimeter out and do a little digging to fix this one!

Disconnect the front and rear sounders, then measure the resistance between
Pin4 on C78 and the Green/Red pin at the sounder.
Pin3 on C78 and the Green/Brown pin at the sounder.
Repeat again for the rear sounder
Pin10 on C77 and the Green/Red pin at the sounder
Pin2 on C77 and the Green/Brown pin at the sounder.

Report back!

[Fraz-ktf]

So your car's control unit in the good vehicle stops that one working but the good car's unit in your car also stops working?

Clearing the codes shouldn't make and difference because that module is classed as "non latching", ie the codes can self-reset.

Open circuit is just a technical way of saying the circuit isn't complete although its strange that its for both chimes - did you move both or just the front? I think what's especially strange here is that the front and rear sounders are on different connectors into the unit and the external wiring is therefore entirely separate. I think you might have to get the multimeter out and do a little digging to fix this one!

Disconnect the front and rear sounders, then measure the resistance between
Pin4 on C78 and the Green/Red pin at the sounder.
Pin3 on C78 and the Green/Brown pin at the sounder.
Repeat again for the rear sounder
Pin10 on C77 and the Green/Red pin at the sounder
Pin2 on C77 and the Green/Brown pin at the sounder.

Report back!

Thanks, will do.

The front sounder was moved over a year ago and has been working perfectly.

I have taken out the PCB on my original control unit, to find a burnt out contact - so that explains that! . . . . but it doesn't explain why the "Replacement" control unit won't work in my car.

I have checked the continuity to the front sounder and it tests ok. Don't know how to check it for the rear sounder as I don't know where the wires go to.

I will check tomorrow, what you suggested, and report back BUT - which / what is C78 and C77 and are the pins numbered?

Thanks again Mirez 

[Fraz-ktf]

So your car's control unit in the good vehicle stops that one working but the good car's unit in your car also stops working?

Clearing the codes shouldn't make and difference because that module is classed as "non latching", ie the codes can self-reset.

Open circuit is just a technical way of saying the circuit isn't complete although its strange that its for both chimes - did you move both or just the front? I think what's especially strange here is that the front and rear sounders are on different connectors into the unit and the external wiring is therefore entirely separate. I think you might have to get the multimeter out and do a little digging to fix this one!

Disconnect the front and rear sounders, then measure the resistance between
Pin4 on C78 and the Green/Red pin at the sounder.
Pin3 on C78 and the Green/Brown pin at the sounder.
Repeat again for the rear sounder
Pin10 on C77 and the Green/Red pin at the sounder
Pin2 on C77 and the Green/Brown pin at the sounder.

Report back!

Results below Mirez 

FRONT
Pin4 on C78 and the BLUE/Red pin at the sounder. = 0.00 on the Multimeter
Pin3 on C78 and the BLUE/Brown pin at the sounder = 0.00

REAR
Pin10 on C77 and the Green/Red pin at the sounder = 0.00
Pin2 on C77 and the Green/Brown pin at the sounder. = 0.00

So I'm guessing that I just checked the continuity from the plug (At the Control Unit end) to the speakers - which check out ok, so it's not a wiring fault, right?

What do you suggest next please?

[Mirez]

Yes that's correct, we are proving the wiring isn't broken and that a circuit would be possible.

Next, We need to prove the sounder itself isn't faulty so again with them out of circuit (so disconnected) and again in resistance mode measure between both of the sounders pins. A value close to zero would be expected.

Potentially, you'll find both read O/C (N/C, -1 depending on the meter) and that they are both faulty - taken out by the control unit failing. Its the only scenario I currently can think of as to why the swap around didn't produce different results!

[Fraz-ktf]

Yes that's correct, we are proving the wiring isn't broken and that a circuit would be possible.

Next, We need to prove the sounder itself isn't faulty so again with them out of circuit (so disconnected) and again in resistance mode measure between both of the sounders pins. A value close to zero would be expected.

Potentially, you'll find both read O/C (N/C, -1 depending on the meter) and that they are both faulty - taken out by the control unit failing. Its the only scenario I currently can think of as to why the swap around didn't produce different results!

Mr Mirez . . . . . you are the Guru, the Oracle and the Saint of all things Broken 

Checked the two speakers and they are shot too 

problem solved.  somehow, despite not getting wet from the burst rear wash / wipe pipe, the controller had shorted out, taking with it, the 2 x sounders.

Thank you so much (Again) for your time and interest in helping me to problem solve. 
you're a STAR 

[Fraz-ktf]

OH NO - I SPOKE TOO SOON! 

Plugged everything back in today and I've still got the same problem.
I put the Control Unit back in the "Donor Car" along with the 2 x sounders and the whole Park Assist System works perfectly 
Swap out the sounders - still works perfectly 
Conclusion - the sounders ain't broken after all

With the known working Control Unit in my car and everything connected, all I can get is the constantly flashing switch.
If I unplug the middle connector (C78) from the Unit, I get a long "Beep" from the rear sounder, followed by just the flashing switch.
(The "Donor Car" does exactly the same when I unplug the middle plug (C78) from the working Control Unit) - So I'm guessing that the rear part of the system is working because both cars react exactly the same when the working Control Unit is fitted but C78 is left unplugged?

The problem seems to be in my car, when the middle plug (C78) is plugged into the Control Unit. (Re-checked the continuity from pins 3 & 4 to the sounder plug and they both come up as 0 on the Multimeter)

What else could be causing this issue do you think?
What do all the other wires do, that are in that centre plug?
Could it be a problem on one of the other wires in C78?
Do you have a wire diagram?

[Mirez]

Ahh bugger!

If you unplug both the connectors at the module and the sounders, have you measured between the pins at the sounder end in this configuration? A resistance check here would confirm the wires are both insulated from each other and not shorted somewhere on the run

[Fraz-ktf]

Ahh bugger!

If you unplug both the connectors at the module and the sounders, have you measured between the pins at the sounder end in this configuration? A resistance check here would confirm the wires are both insulated from each other and not shorted somewhere on the run

will do that check tomorrow and report back.
what reading would I be hoping for?

[Mirez]

You want a reading of N/C, -1 etc to indicate the circuit isn't complete. If you have a value then the lines are shorted somewhere