Alarm failure, horn beep after closing the car

[Doohan]

I'm trying to fix this problem since 3 years or more... finally got my PIWIS, the fault code memory says "33", at page 90 - D 41 of the workshop manual it says "Replace passenger compartment monitoring sensor", I replaced it for about 130€, nothing changed... same fault code!

So, I started to do all the tests points of the workshop, from number 22 to 36, and the only thing I discovered was an issue on test point 32 step 3, now the solution is to "check the wiring harness for pinches and chafing damage"... My question: is there any simple way to test this wiring harness??

[JFP in PA]

First of all, stop randomly changing parts and find out what is causing the alarm fault. These cars store the last ten alarm faults in computer memory, scan the car with a PIWIS unit or the Durametric software and you will know for sure where the issue lies. Quite often, the two favorites are the armrest contact switch, or the radio security ground wire.

[Doohan]

I'm not randomly changing parts, the workshop manual literally says "Replace passenger compartment monitoring sensor" for the error code 33.

[logray]

Did you replace both of the compartment sensors?

IIRC there is one near the reading light and a second near the windshield.

For wiring, you could test for continuity between the alarm module and the sensors.

[Loren]

Something else to consider is if someone wired a radar detector using the wiring at the headliner bulkhead. If so, they may have damaged the wiring.

[Doohan]

Did you replace both of the compartment sensors?

IIRC there is one near the reading light and a second near the windshield.

For wiring, you could test for continuity between the alarm module and the sensors.

I changed the one (the unit) near the reading light, where is the other one?

Something else to consider is if someone wired a radar detector using the wiring at the headliner bulkhead. If so, they may have damaged the wiring.

No radar detectors in Italy :(

[logray]

I changed the one (the unit) near the reading light, where is the other one?

Sorry, I was thinking of the sensor at the front part of the dash close to the window. I believe that is a sun sensor and alarm light indicator, not a passenger compartment sensor.

[Doohan]

Update...

I finally had a new sensor (number 2) from the dealer, now I have fault 33 & 34!

I do not have the Alarm Siren and the tilt sensor, I checked the compartment monitoring sensor by closing the car with the remote and keeping the window open, after 30s if I move my hand inside the car the alarm horn goes on! so the sensor is actually working?!

[logray]

I am wondering if your alarm module is damaged, perhaps from water.

[Doohan]

I'll open it, looking for corrosion or other... :(

[Doohan]

No signs of water, corrosion, flood or other, anyway I cleaned the mainboard with a spray cleaner but nothing changed!

The unit is a M534

996 618 260 06

Edited December 19, 2011 by Doohan

[logray]

Have you tested the wiring?

[Doohan]

From the unit to the sensor? yes, apparently no problems

[logray]

I assume this is a RoW car by the M534 option. Perhaps the coding of the unit has been changed for USA or otherwise since I see you are in two locations?

In a more likely case, since you've eliminated the wiring and sensor, whats left in the picture is the alarm module.

That unit 99661826006 costs about $275 USD at discount, but also needs to be coded by a shop who has a PST2 or PIWIS.

Since throwing parts at it doesn't always work, it might pay to take it to a shop who has experience troubleshooting these issues (and could also program a replacement unit).

[Doohan]

Thanks for the help, yes, it's a RoW car that actually I drive in Italy, it will be very difficult to find a shop with this type of experience here :( I'll try anyway! Thanks again, I'll post my results!

[Doohan]

Just founded a working unit in the Netherlands for 120€ I have the PIWIS cable with Durametric software can I code it by myself?

[logray]

You'll need to get your cars IPASS codes which only the dealer or authorized shop with a PIWIS subscription can obtain. If you show proof of ownership a shop might provide you with the codes.

Also, not 100% certain but you might also need the donor cars codes, which you probably won't be able to get. Or at least there was something about alarm unit coding limitations on used units. Lorens better at this stuff than me, so maybe he is reading this thread.

[Doohan]

From Durametric cable I also have the error code P1571 n°39 on the motronic

[logray]

P1571 39 Immobilizer - Open circuit/No Signal

Looks like you still have some wiring issues to sort out...

[Doohan]

I've just seen that I have my GPS Alarm unit module fitted right on the top of the immobilizer! could be this after all?