 | Home > Tdi > 300tdi Alarm and Horn sounding when reconnecting battery? |
 
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| Mining Subsidence Stu Member Since: 06 Mar 2024 Location: Cornwall Posts: 32   
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It's a nightmare. Mine was playing silly
 and I wired it out and the problem was the alarm. Take the 10A fuse out on the right top and it will shut that thing up. Mine would blow the 5A fuse below and did all sorts of funny things. I put a 7.5A fuse in and it worked, but it was always a matter of when it was going to cause problems.
I got rid of the truck and got a 200 as a replacement. I'd google how you find the OBD port and switch the alarm function off, per foreign trucks with no key fob. It's a mystery Mine would not crank occasionally. |
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3rd Feb 2025 6:28pm |
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| KiwiNCFC Member Since: 14 Jul 2019 Location: East anglia Posts: 49 
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Thanks for that. Still having issues. Not very popular with the neighbours after going off at 2am last night. Only way I could stop it was by disconnecting battery. I bought new battery thinking it was getting low causing havoc with the 'alarm ecu' but nope still causes issues. Seriously
me off now!
I need to rip the immobiliser and alarm out! But I'm not sure where to start?! The weird thing is I bought an immobiliser bypass plug to plug into the spider but thr immobiliser still works? As in I have ti press the fob to get rid off the red light on the dash so what's the point of the bypass plug? So frustrating! |
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3rd Mar 2025 9:14pm |
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| Mining Subsidence Stu Member Since: 06 Mar 2024 Location: Cornwall Posts: 32
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The 10A fuse will sort that out. Get it out. I removed my black box and the problem persisted. It was the alarm, which is not the black box. Everything is connected to it. The switch under the bonnet and the door switches. There is an OBD connector and you can switch the whole alarm/immobiliser off via it. Export models have no key fob, but have the boxes. I have a feeling if you deactivate the alarm via the OBD it will sort this problem out.
It was a &^%&^%ing nightmare. Mine had a mind of it's own. I got a 200 because of this. |
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3rd Mar 2025 9:18pm |
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| Mining Subsidence Stu Member Since: 06 Mar 2024 Location: Cornwall Posts: 32
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To add. The immobiliser is the thing which the alarm sends the signal to to kill the diesel pump and the starter motor. I wired mine out (same as the plug). The alarm (look at the circuit diagram) is like the heart of the wiring loom. I don't think you are getting it out. Get that 10A fuse out. Mine did random stuff and blew the 5A fuse. I ended up putting a 7.5 in and it sorted it (but how/why/what/where). It was always a nightmare when it was going to just decide not to start.
Taking the 10A fuse out will at least shut it up. I also removed "all of that " from by the left headlight. |
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3rd Mar 2025 9:23pm |
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| KiwiNCFC Member Since: 14 Jul 2019 Location: East anglia Posts: 49
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Thanks for your input bud, really appreciate it! So is that 10a fuse just for the alarm or the horn? Had an occasion where the horn was permanently on and pulled a wire off the back of it and that stopped that but I think the alarm had been going off for a while as I was out all day and when I came back I heard a buzzing which was from the horn and I checked the battery voltage and it was at 10.4v so it must have been going constantly for hours draining the battery! I also had a period of time last year where on turning the key I had nothing. The only way to start the car was to jump start it which led me down the new battery path as the landy is my weekend car and I assumed the battery was draining! I also had another occurrence where the starter motor (which was 2 months old) was jammed on when turning the key and I had to disconnect the battery to solve that! New starter fitted and never occurred again! Being a weekend car I don't drive it enough to fully convince myself that an issue has been solved!
The ECU disabling via obd is interesting...I've seen the obd port and assumed it was just there for testing at factory but I'll phone a few independents up and see if they can disable that way. Although, if the ecu modules are a ticking time bomb, what's to say a disabling of the ecu via obd will one day reactivate itself due to a dry solder joint or something! I'll update this with info once I get to the bottom of it! Might take a while! |
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3rd Mar 2025 10:58pm |
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| Mining Subsidence Stu Member Since: 06 Mar 2024 Location: Cornwall Posts: 32
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It's a nightmare. I went from my 300 which was the most reliable vehicle in the world with nothing apart from chassis and bulkhead rust to my 200, which had a 8 years old total no expense spared restoration. Currently have done new gearbox, new steering box, new injector pump, new exhaust, overdrive, power steering belt shriek nightmare, etc, etc, etc. Oh, the ignition switch nightmare. You have that to come. It's like the immobiliser but even more maddening. Oh, and the headlights mystery (one side stopped working). etc.
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3rd Mar 2025 11:09pm |
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