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Old 10-21-2007, 12:17 AM
Join Date: Oct 2007
Location: West Coast of the East Coast on the southernmost region of North America, Sarasota Florida
Posts: 1
Question Security System Problems on 92 SL 500

Anybody know how to disable the security system on the 92 SL 500? All of a sudden, when I lock my car, the security system can't be re set, the fob doesn't work and when I use my key, it still stays armed. Made it really difficulty to drive home...

If I disconnect the battery for about a week, the system will reset, but if I lock the car, it sets the alarm and then cannot be reset.
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Old 10-21-2007, 12:32 PM
Registered User
Join Date: Mar 2003
Location: Milwaukee Wisconsin
Posts: 1,150
The ATA ( anti theft Alarm ) is very well integrated into many vehicle systems. I don't know if simply unplugging the module will disable it and allow the car to start, since it controls a starter relay. I've never had a problem with mine, so no experience. If you are electronically inclined, you can build a simple scan tool and look at the diagnostic trouble codes. I believe the info I have for my 1991 is also applicable to a 1992, but these systems changed often over the early years, so no guarantees that this is correct. The 16 pin diagnostic connector is under the hood on the right side under a small cover near the strut mount. The ATA module itself is in the trunk, upper right side.

Anti Theft Alarm Codes.
The codes blink out on an LED (1 blink = no errors) when pin 11 is momentarilly grounded. To clear an error, close switch for 4 to 8 seconds.

DTC Readout Possible Cause of Failure
1 No fault found
2 Alarm activated, trunk sensor circuit
3 Alarm activated, engine hood circuit
4 Alarm triggered, glove compartment
5 Alarm activated, rear circuit Console compartment circuit
6 Alarm activated, front door circuit
10 Alarm activated, radio circuit
12 Alarm activated, ignition circuit
14 Alarm activated, brake circuit
19 AT Control module faulty
20 Left front door actuator, No ground connection
21 ATA disarmed, Starter lock-out relay module. short to circuit 30
23 ATA armed, Open to circuit 30

The scan tool is just a push button switch and LED wired together.
You can do a forum search and find info on how to build it and use it.

0______/ ____0______LED__/\/\/\/\/\_____0 12V+
pin 1 SW pin 11 C A 1K resistor pin 16

Connect wires of Scanner as follows (Model 129.061, 129.066)
16 pin Data Link Connector
Socket 11 (switch)
Black Socket 1 (-) ground
Red Battery (+) (LED)

This will only work on early models with the 16 pin diagnostic connector. Later systems were much improved and require complex computer scanners.
If this is all GEEK to you, take your car to a professional.
Resistance is Futile.
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Old 10-21-2007, 07:57 PM
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Join Date: May 2001
Location: Las Vegas, Atlanta
Posts: 669
Originally Posted by Mikegb02 View Post
Anybody know how to disable the security system on the 92 SL 500?
Remove the connector to the alarm module shown here: malfunctioning alarm system. I believe this can be done on '92 and older R129s without impacting any other systems.
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