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Just over a month ago, I posted a message about my 97 900 SETC dying suddenly at a stoplight. Initially, I thought it was the common “DI cassette failure”. But, when I finally got serious about sleuthing, I found the problem went much deeper. Referencing the electrical schematics at ALLDATADIY.com (membership is $25/year…great site for the serious DIYer) and using some basic troubleshooting logic, I was able to get her back on the road within two days.
The problem turned out to be a faulty alarm control module. The odd thing is the remotes were working with no problem, the alarm armed and disarmed with no problem and the intruder horn sounded, if I simulated breaking into the car (so, initially I was deceived, because everything “acted” normal at first glance). However, I learned that the alarm control module also “immobilizes” the car in a theft situation. When the alarm module is operating normally, a theft prevention circuit (Saab calls this the "3-circuit breaking" function) immobilizes the car by preventing power from reaching the following components: the fuel pump relay, the starter relay and the Engine Control Module (creating an immovable object…unless of course, the perpetrator has a tow truck), in a theft situation. Here’s the kicker: A component within my alarm control module, which controlled the immobilization circuit, malfunctioned and was preventing power from reaching two of the three components: the fuel pump and Engine Control Module. Therefore, the starter would crank, but the engine was getting no spark or fuel.
My interim solution (until I decide to drop $500 on a new module) involved bypassing the three legs of the immobilization circuit (rather than the whole module). That way, I was able to keep the benefits of the remotes and arm the alarm (at least).
So, if your car dies without warning and you find no spark at the DI cassette, check for voltage into the fuel pump relay, the starter relay and ECM feed from the alarm control module. If you find none at all, or a combination of them, the immobilization circuit of the alarm module is likely to be toast (remember, normal operation of all other alarm functions can be misleading).
Paul
posted by 68.33.17...
, Wed, 16 Oct 2019 15:26:26, Wed, 16 Oct 2019 15:30:09, Tue, 15 Oct 2019 10:20:42, Wed, 16 Oct 2019 15:31:44
1, Fri, 11 Oct 2019 18:46:02
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