Alarm not working properly

Hi,

By chance, do you know if it is a factory alarm or an aftermarket one that was installed? If it is a factory module, I don't feel it would be drivable. Otherwise, anyone could remove it to bypass the anti-theft system.

Here is what I suggest: The vehicle should the CAN-bus scanned. CAN stands for controller area network. Basically, all the modules and computers are tied together via a few wires. By doing this, it should identify if there is a fault stored in the module. Otherwise, the cause becomes a guessing game.

In my mind, I would not like to see you just replace the module without testing. I can't imagine it will be an inexpensive part and you don't want to be wrong.

Here is a quick video showing how it's done:

https://youtu.be/u-4syLc-ifQ

If possible, have that done, and let me know what codes are found. If you are not able to, let me know if you are able to start the vehicle without the module, if the starter is working, and any and all symptoms related to the problem. One way or another, we'll get it figured out what is happening.

Please keep in mind, this simply could be a loose door switch, hood switch, or anything that could lead to the vehicle thinking it's being stolen.

Let me know.

Joe

It is a factory module.

Hi,

Okay, then if you scan the can-bus it should help us narrow things down. Is it possible for you to have that done?

Joe

Which brand and type of scanner will work with my car? several models at AutoZone. workers at AutoZone don't know what is CAN.

Hi,

CAN stands for controller area network. Basically, picture several computers at home or work that are tied together via a few wires. That is how the computers/modules are in your vehicle. They communicate with each other via a few wires connecting them, the CAN bus system.

On older vehicles, this design wasn't used, so it was difficult to retrieve codes that were stored in other computer modules.

I attached a pic of one at AutoZone that has the ability to communicate with the CAN below. You can get these for much less money on Amazon, but I thought since you went to AutoZone, I could show you what they have.

Let me know if this helps or if you have other questions.

Take care,

Joe

I was able to scan the bus and I've got a P0705, which is the transmission range selector circuit. would this cause the car not to crank?

Hi,

Yep. If the computer thinks it's in a gear other than park or neutral or receives no signal, it won't crank. When you place the transmission in park, does it indicate correctly? Also, do all gears coincide with the indicator?

Let me know.

Joe

repaired the cables that are shorting out with each other due to worn insulation. no more fault codes after scanning this time. however, the engine still would not crank. the gauges flicker same time as the 409 relay clicks. cleaned all grounding spots. what could it be?

Hi,

Are you certain the battery is good? If you are, we need to check for power at the S solenoid at the starter. You will need a helper to do this. The wire color at the starter motor is red with a black tracer. It will be the one which is smaller in diameter.

Have a helper turn the key to the start position while you check for power at the starter.

I attached the wiring schematic below for your review. I had to cut it in half to make it readable, but I did overlap them so you can follow from one to the next. Additionally, I highlighted the circuit.

The idea that the gauges jump when the relay clicks really sounds like a poor connection at the battery or a weak battery. Make sure to check both.

Let me know what you find.

Joe

See pics below.

Finally found the problem. The car has a defective negative cable from the battery to the engine block. Replaced battery cable and it started immediately. Thank you so much for your help.

Hi,

Thank you for the update. I'm glad to hear it was a simple repair and you fixed it.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care and I hope you have a great Christmas.

Joe

Thank you. While I was warming up the engine, I noticed the tachometer instrument fluctuates from 1,000 RPMs to 7,000 RPMs and it keeps moving, while the actual engine speed remains the same at 800 RPMs. What is causing this behavior?

Hi,

The signal is coming from the ignition coil (circuit 1) and VW is known for corroded connectors causing issues with the tachometer. If you look below, I included pics showing the coil, schematic, and definition of circuit 1.

Locate the coil and inspect the connectors to it (not the coil wire to the distributor).

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.