Alarm System - Tester Upgrades
Date: April 1998Order No.: S-SI-MBNA-58/98
Supersedes: S-SI-MBNA-58/80, April 1995
S-SI-MBNA-58/86, December 1995
Group: 58
Revision: Self-fabrication solution eliminated, additional information on testing Model Year 1993 and later vehicles.
SUBJECT:
MODELS 124 AND 201 WITH ANTI-THEFT ALARM (ATA) AS OF MODEL YEAR 1993 UPGRADE TO ALARM TESTER 924 589 00 21 00
Becker of North America, Inc. offers an upgrade and modification service for the Mercedes-Benz alarm system tester (described in Service Information 82/42, November 1987) to include diagnosis of model year 1993 and later vehicles.
Self-fabrication of an adapter harness to allow diagnosis of model year 1993 and later vehicles as described in Service Information MBNA 58/80, April 1995, is no longer recommended.
Dealers can send their MB alarm system tester directly to Becker of North America, Inc. (address below) to have these features installed for a flat fee of $70.00 (parts and labor included).
Becker of North America, Inc.
16 Parkway
Upper Saddle River, New Jersey 70458
Telephone: (201) 327-3434
Note:
The flat fee quoted above assumes the MB alarm system tester is fully operational and functional. Any required repairs to the basic tester will be charged extra prior to the upgrade and modification.
The modified tester can be identified externally by the addition of a toggle switch on the control module itself (enlargement, Figure 1).
All modifications are incorporated internal to the control module.
Special information regarding model year 1993 and later vehicles:
The Mercedes-Benz alarm system tester detects and stores signals to indicate which anti-theft alarm (ATA) sensor caused the ATA to activate. It is designed to store an ATA sensor activation only when the ATA is armed, as indicated by a ground signal at pin 1 of the 14-pole connector on the ATA control module (N26). Pin 1 of the 14-pole connector is open-circuited when the ATA is disarmed.
This function applies to 124, 201, 126, and 107 model vehicles equipped with ATA up to model year 1993.
As of model year 1993, the function of pin 1 was inverted. As a result, pin 1 is grounded when the ATA is disarmed and is open-circuited when the ATA is armed. This is used to control the starter lock-out relay module (K38). Due to the above mentioned functional change, the alarm system tester stores sensor activations only when the alarm system is disarmed, and therefore is not effective in diagnosing ATA system complaints.
Modification of the alarm system tester will however, allow testing of both versions.
Exception:
As of model year 1993, ATA control modules having the part number 126 820 24 26 (and possibly other modules) cannot be diagnosed with the modified tester due to an additional circuit change. The function of pin 1 in this so-called "type 2" unit was changed again. Instead of switching between an open circuit and grounded state, it switches between an open circuit state and a low impedance (Approx. 56 Ohms to ground) state. This impedance is not sufficient to operate the test modification relay, thus the tester cannot function in the "MY93 and later" position. The exact effective vehicle identification numbers (VIN) of this running-change remain unknown.
Special Tool availability note:
The Mercedes-Benz alarm system tester, Special Tool number 924 589 00 21 00, is no longer available for new purchase.