anti-theft response not cranking (not IMMO?)

[maxmose]

Hi all, I'm pretty new here and this is my first post. Hope I'm posting in the correct section.

I've read what I could find on this topic, and I haven't found anything that seems to describe my situation exactly. Any guidance would be appreciated.

I have a 2001 TDI Jetta. The fob stopped working years ago after it got wet. I never bothered to replace it, and just locked the doors manually with the key. I often use the valet key, because it goes on my key ring, but I still have the switchblade style key, the buttons just don't work. Recently, I've been having some minor electrical issues, where the trunk won't open with the switch on the driver's side door. This happened a while back, and then it started working again, then stopped working again. When I need to open the trunk, I can do so with the master key by turning it (hard) to the left.

Today, I did something stupid, where I triggered the alarm. The window was down, and the car was locked, and for some reason instead of unlocking it, I reached through the window and opened the door. The alarm went off, and I only had the valet key on me. I closed the door, locked and unlocked it with the valet key, and the alarm stopped honking. Then... when I tried to start the car, all the dash lights came on as usual, but when I turned the key all the way there was nothing. No clicking solenoid, nothing.

I tried a few things like locking and unlocking the car with the master key, opening and shutting the trunk, disconnecting and reconnecting the battery, once leaving it disconnected for a while, once reconnecting it with the master key in the on position, leaving the key in the on position for 15 mintues, etc. Nothing, I still get no action when I try to crank the ignition. The IMMO dash light is not on (it lights up with all the lights when I first turn the key, and then goes off with everything except the glow plug light, which goes off a second later.

Any thoughts what's blocking my starter from starting? Is it an antitheft feature? Anyway I can resolve the problem without a working fob?

 

[Alchemist]

The starter circuit is fairly simple, and neither the immobilizer nor the key fob has anything to do with it.

There is a heavy braided wire between the solenoid and starter which is prone to corrosion. If this wire is not making good connection, the symptoms will be exactly as you describe.

When you turn the key to the start position, power is sent from the key switch to either the clutch position switch and relay, or the Park Neutral position relay. From there it goes to the starter. The wire from the relay is know to break near the starter, but odds are the problem is the heavy wire has corroded off.

Another possibility is the ignition switch has failed, or is failing.

HTH

 

[maxmose]

Thank you for your reply!

I managed to get my fob to start working again by taking it apart and cleaning some corrosion around the switches. As your response suggests, this did not resolve the problem.

I’m pretty inexperienced, but I will try to locate the components you’ve mentioned to continue diagnosing the problem. Thanks again.

 

[maxmose]

@Alchemist, wondering if you have any insight about the starter issue possibly still being related to the alarm system (while not the immobilizer), as part of the central convenience module.

In this guide to troubleshooting starter issues, they say, “The alarm system can also be faulty and prevent the ignition signal from reaching the starter solenoid at terminal 50. The alarm is part of the central convenience module (CCM) which also controls power windows, remote keyless entry”.

 

[maxmose]

I pulled the starter and it tested bad. Replaced it (along with solenoid) and it cranked up nicely. I guess it was just a coincidence that it failed for the first time right after I set off the alarm. Bizarre, but luckily turned out to be a job I could do myself.

Thanks for the help on this.