Date: 27 Oct 2000 15:35:51 GMT From: dsjkallennopsamcom (DSJKALLEN) Subject: Re: Curious Check Engine Light?
The EZK ignition system used in the 900S features built-in diagnostics that detects and stores in memory coded information regarding ignition system faults. These fault codes can be read-out through flashes of the "Check Engine" light. First of all, before troubleshooting an EZK fault and the flashing "Check Engine" light, check for broken or loose engine mounts or brackets. Follow this procedure: Start the engine and allow it to reach operating temperature. Then, increase RPMs to above 2,000 RPM. Count the number of times the "Check Engine" light flashes. At higher RPMs, the "Check Engine" will flash at a faster rate, but still a certain amount of times in a group of flashes. The number of flashes determines the fault in the ignition system. In your case, it is flashing 4 times. But, it then stays on. In your model year this can signify two things: 1). The 4 flashes point to a failure with the EZK ignition system. Specifically, the 4 flashes points you to a failure of any of the following components: the knock sensor (the typical failure), the knock sensor wiring harness, or the EZK ignition control unit itself. Suspect the knock sensor first (mounted on the block beneath the intake runners, between cylinder 2 and 3). 2). A steady-on "Engine Check" light means the LH fuel injection system has detected a fault. With a '91 900S, you have the LH 2.4.2 (the latest for the classic 900s) fuel injection system. This can be identified by the 3-wire AIC valve, and a "plastic" AMM (Air Mass Meter) without a mixture adjustment screw. The faults within the LH fuel injection with a steady-on "Engine Check" light can be one of a number of things. This info on fault codes is specifically address in the Bentley Saab 16-valve manual on pages 240-6 and 240-7. If you have access to a fax, I would be happy to fax this info to you. Otherwise, I would strongly suggest you purchase one of the manuals -- available at your Saab dealer or from Bentley direct. Note: In my daughter's '87 900S (with the same EZK ignition system, but with the earlier LH 2.2 fuel injection system, the same 4-flash fault code was caused by a bad knock sensor. Once I replaced the sensor, everything was fine. However, the "Check Engine" light never was in a steady-on state -- always a 4-flash sequence. Don Allen Urbana, IL