Can anyone give me advice on how to disable the alarm functions without losing central locking and turn signals?
Recently I had to disconnect the battery to recharge it. When reconnected, the alarm system came on (siren/horns/flashing lights). I followed the emergency disarm instructions (open door, ignition switch off-on 3 times)–siren/horns/flashing lights still on. I purchased a replacement security module (DPP1057 XX) and borrowed another from a friend–alarm turned off, but no turn signals and no central locking (I later figured out that each of these is programmed for the specific car). The on-off switch in the central console had no effect (but the instructions said it is operative only when the system is disarmed). From what I can tell, the 1993 & 1994 share the same operating procedures, but earlier ones are different. I’m assuming that the 1995+ years also are different.
I removed the module–the car starts and runs fine, but no turn signals and no central locking. As best I can tell from the wiring diagram, the alarm module manages some functions directly (such as the siren–which I unplugged) and other functions (turn signals, lights, horns) through signals to the central processor. So perhaps I could cut some of wires ? Or send some to ground? Or put 12 volts on some? The candidates appear to be LS44-4, LS44-8, LS44-12. Or maybe disable some of the inputs (LS43-11, LS43-5, LS43-1, LS43-2, LS43-3, LS43-4).
Except for these faults, the car works wonderfully well–but with the faults, I can’t safely drive it. Many thanks in advance for any suggestions (or even hints)!
Peter
Peter, welcome to Jag-lovers. I would NOT start cutting wires in an attempt to work around this issue. Because you appear to be familiar with wiring diagrams I would start by checking the inputs for proper operation. For example LS43-1 is the trunk switch, which should go to ground when the trunk is open and therefor have no continuity to ground when the trunk is closed. Etc. etc. etc.
The security system manages few functions directly. Most are controlled via a central body processor unit (BPU) on the 93/94 cars.
In have to concur with Mike. Check inputs from doors, trunk and hood switches first. If one is “open”, this could be the source of your problem.
The security modules are not vehicle specific from my knowledge as far as central functions are concerned, since there is no immobilizer. This has changed starting with the X300 though.
Security flash is controlled via the central processor, connector LB61, Pin 32. +5V is inactive, pulsed signal (probably 5V) is flash. So you probably want to put that on +5V permanently to regain regular turn signals. I didn’t have to try that (yet) because my security module is functional.
Central locking is similar, function can be restored easily. I did that using an aftermarket RF remote sending a pulse to ground on LB 61 pin 38 to lock/unlock.
You may just want to try the above and see if it works. Otherwise, your central BPU might be defective.
Help still requested–alarm still triggering, but some sensors may be not operating properly.
I checked several wires on the connectors, with the battery and security module disconnected. On LS43 (inputs), I got ground on driver’s door open, passenger’s door open (but all doors were closed during these tests. Also ground on Door state unlock, ignition position 1, and unknown (socket 11).
.
I got open on Shock sensor input, hood open, intrusion breached. I got resistance (about 10 ohms) from the trunk open sensor Help. . . . Thanks for any additional suggestions
Peter, just to confirm - you disconnected the 20-pin connector from the security ECU located on the left wheel arch, inside the trunk, beneath the fuel filler?
The door switches which are monitored via LS43-3 (purple wire) and -4 (purple/red) are in the passenger and driver door latches on opposite sides of the car. It seems unlikely both of those switches would fail at the same time. I would suspect damage to the wiring for those inputs.
the door lock “status” switches are micro switches sitting on a small pcb in the door latch assemblies. They do break; from memory one pin of the micro switch on my passenger door either fractured or had a cracked solder joint. In your case, I would check both left and right sides. And I agree, check wiring first and check the switches from the connectors behind the door panel before dismantling the door latch units. Because getting to the micro switches in the doors is a major PITA.
Yes. A bit easier-said-than-done: The cables containing the plugs are so far into the upper wheel arch that it is impossible to measure anything. I removed the rear seats, some internal trim, a gasket, some foam—was then able to pull the cables into rear of the interior cabin. Then I was able to easily get to the wires for all three connectors used with the security module.
The input connector (LS43) signal leads (such as door open, hood open etc) are either open or ground, correct? If yes, which situation (open or ground) tells the module that all is well? Do you know if any of these input signal leads is supposed to send something in-between (not ground, but 10 or so Ω
As you can see, not all circuits are inputs to the security system ECU. Specifically, -11 and -19 are outputs to the intrusion sensor (if fitted) and the alarm antenna shield (hmmm…). Then there is -20 which is an input from the alarm antenna (within the rear windscreen), which I would expect to not be grounded; it may show some resistance just as television and radio antennae do.
That’s why I suggest to measure close to the door switches first.
There are 3 switches in each front door. (1) Key barrel (central locking only), (2) lock state (central locking and security), (3) door open/close state (security only)
My strategy would be: Remove door trim, identify the connectors in the lower rear corner of the door (3 or 4 separate connectors). Measure (2) if ground is present in locked or unlocked state depending on the door lock state (see page 51 in the electrical manual). For (3) see, if ground or 5V is present on the door state (open or closed).
And ground should be ground, 10 Ohms resistance look more like a ground problem to me.
Can you point me to a link to that electrical manual?
I have the 1000+ page shop manual, but it focuses on repair/replace procedures and not so much on how things work. No luck so far finding a 1993 electrical manual.
Peter - Guido posted a link to the guide - see post #8 earlier in this thread. You may have to copy the link and paste into your browser to get it to work.
