What does this coaxial cable do?

[WorkInProgressK]

Found this coaxial cable under my seat.

Located right next to the immobilizer it's too small to be radio standard.

Does anyone know whats it's purpose?(other then pass electrons.)

Thanks

[JFP in PA]

Aftermarket addition.

[Qmulus]

That is the antenna connection for the alarm/immobilizer module for the remotes. You need that. It plugs into the module about an inch to the left in your picture, just to the outside of the blue connector.

The "antenna" is just a piece of coax (some flavor of RG174) run with the harness with the shield stripped away for the appropriate length (a bit over 9" for 1/4 wave) which acts as antenna. Your remote range will be greatly reduced if that is not connected. Range was obviously not a huge consideration, so they didn't spend much/any time on antenna design. This is a very common way of running the remote antennas. The M531 module used with the earlier two-button remotes also has a coax run in the harness, but they did not bother using an RF connector, and the signal and shield wires are incorporated in the main blue connector.

There, more than you wanted to know!

[particlewave]

I've had my immobilizer in and out several times and I don't have a cable like that. There also isn't anywhere on mine where something like that would plug in (I just looked).

[Qmulus]

Originally Posted by particlewave

I've had my immobilizer in and out several times and I don't have a cable like that. There also isn't anywhere on mine where something like that would plug in (I just looked).

Well, I just so happen to have an M535 996.618.262.03 module right next to me. From what I have seen, the cars with three button remotes and the M535 module have the coax connection. The cars with two button remote and M531 module have the coax run through terminals the blue connector. Either way, you have the coax antenna in the harness, but on the M535 they split it out and put it through a proper RF connector. So, I would say that you have an M531 alarm/immobilizer module in your car.

A picture is worth a thousand words, so here you go.

[WorkInProgressK]

Originally Posted by Qmulus

That is the antenna connection for the alarm/immobilizer module for the remotes. You need that. It plugs into the module about an inch to the left in your picture, just to the outside of the blue connector.

The "antenna" is just a piece of coax (some flavor of RG174) run with the harness with the shield stripped away for the appropriate length (a bit over 9" for 1/4 wave) which acts as antenna. Your remote range will be greatly reduced if that is not connected. Range was obviously not a huge consideration, so they didn't spend much/any time on antenna design. This is a very common way of running the remote antennas. The M531 module used with the earlier one-button remotes also has a coax run in the harness, but they did not bother using an RF connector, and the signal and shield wires are incorporated in the main blue connector.

There, more than you wanted to know!

Thank you for the info! I am excited about the prospect that this might be the reason why my remotes never worked. But I curious to know why it was unplugged. Maybe the previous owner removed the module to clean under it? Or could it be a shop trying to make an extra buck. I will try to look where it goes tonight.

I will consider relocating the immobilizer while the chair is out or holes in floor board+ grommet.

Thank you Qmulus. The only info I found was about the 996 immobilizer repair talking about a coax, thanks for confirming.

!!!! Thanks for the picture. (I am glad I incorporated the ecu number in the picture.)

[particlewave]

Good info

I've also never heard of a one button remote. I've only ever seen 2 and 3.

[Qmulus]

Originally Posted by particlewave

Good info

I've also never heard of a one button remote. I've only ever seen 2 and 3.

Oops, you are right. The M531 uses two button remotes, not one. The M535s have three. I will fix the posts. I hate posting incorrect information.

[Qmulus]

Originally Posted by WorkInProgressK

Thank you for the info! I am excited about the prospect that this might be the reason why my remotes never worked. But I curious to know why it was unplugged. Maybe the previous owner removed the module to clean under it? Or could it be a shop trying to make an extra buck. I will try to look where it goes tonight.

I will consider relocating the immobilizer while the chair is out or holes in floor board+ grommet.

Thank you Qmulus. The only info I found was about the 996 immobilizer repair talking about a coax, thanks for confirming.

!!!! Thanks for the picture. (I am glad I incorporated the ecu number in the picture.)

The odd thing about the RF connector is that it is not locking and quite easy to pull out. You could pull it out by accident if you weren't careful.

Personally, I don't like the idea of holes in the floor, but YMMV. On a stock car relocating the alarm/immobilizer is not an easy task.

[jimk04]

I have that connector floating about under my centre console and I need to fire my remote right in through the windscreen for it to work.....might be onto something here!

[particlewave]

Originally Posted by WorkInProgressK

I will consider relocating the immobilizer while the chair is out or holes in floor board+ grommet.

Pop it in a $3 Rubbermaid container and be done with it.
Please don't drill a hole in your car.

[The Radium King]

have a look at what audi uses for this. just got a 2002 audi allroad and the immobiliser is in the same place, but in an oem waterproof case similar to a pelican case - might be useful to visit a wreckers and see if they have something.

[Qmulus]

Originally Posted by The Radium King

have a look at what audi uses for this. just got a 2002 audi allroad and the immobiliser is in the same place, but in an oem waterproof case similar to a pelican case - might be useful to visit a wreckers and see if they have something.

I am VERY familiar with Allroads... You must be a glutton for punishment! (I can relate, I have had a '00 A6 2.7T 6 speed sport for 16 years now...) The problem is those modules still get wet even with that box. More so with the transmission control unit that is on the passenger side floor and the ESP module as well. Make sure you clean out the drains on the plenum near the battery. They tend to fill up with debris, and in big rains water will come in around the cabin filter and down onto the floor. I don't get Audi's tendency to put electronics in places that tend to get wet. I have a big box of Bose amplifiers from newer Q7s and A6s that got wet. They are usually repairable, but it takes the whole MMI system down when it happens.

Just to be clear, the immobilizer is in the cluster on your Allroad. The module under the driver's floor is the Central Convenience module, that is similar to what the Boxster has, but has no immobilizer functionality and no where near the number of issues with them.

[The Radium King]

argh, i hear you. had the seats and carpet out to fix the little hose that runs washer fluid to the rear hatch, replaced the two front suspension airbags, just got the compressor repair kit in the mail to fix that, replaced one door lock mechanism because of a sticky door switch (two more to go ...) flushed the heater core but have to have another go at that to get the heater working better, have an exhaust gas temperature sensor to jumper, replaced two injectors, two front axles, the g65 sensor is throwing a code (hoping just need to top up refigerant) and also getting a transmission gear sensor code that everyone in the audi internet world seems to get and no-one has a soln for. nice car though.

[Qmulus]

Originally Posted by The Radium King

argh, i hear you. had the seats and carpet out to fix the little hose that runs washer fluid to the rear hatch, replaced the two front suspension airbags, just got the compressor repair kit in the mail to fix that, replaced one door lock mechanism because of a sticky door switch (two more to go ...) flushed the heater core but have to have another go at that to get the heater working better, have an exhaust gas temperature sensor to jumper, replaced two injectors, two front axles, the g65 sensor is throwing a code (hoping just need to top up refigerant) and also getting a transmission gear sensor code that everyone in the audi internet world seems to get and no-one has a soln for. nice car though.

You can replace the microswitches in the door latch mechanisms so you don't have to replace the whole mechanism. You can get the correct sealed switches with the integrated wires from a few sources. These are actually pretty much the same as those on Boxsters, which are actually identical to the latches used on Audi TTs.

If at all possible, do NOT use Chinese axles (FEQ, URO, etc.). They don't last and are not rebuildable. OE rebuilds are a bit more, but last and are rebuildable. If you just need boots, don't fall into the trap of getting a replacement Chinese axle just because it doesn't cost much more or may even be cheaper. Lots of shops did this, and now are having them fail like mad and have to spend big $$$ to get new OE axles or will be replacing them multiple times due to vibration or just plain failure.

You cannot simply jumper out a defective EGT sensor. They need to put out the right frequency or the ECU will be unhappy. I am working on replacement internal circuit boards for the EGT sensors to replaced failed OE boards. As you know the EGT sensors are $$$, but a replacement board should be reasonable. You can also get the EGT sensors coded out in the software, but that is not a great idea IMO.

Is the code you are getting for "Incorrect gear ratio"? If so, there is a solution, but it is not what people want to hear.

All normal Allroad/C5/2.7T stuff. How are your upper and lower forward control arms?

Hmmm, maybe we should take this to PM.