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Re: ECU compatibility-LONG- SOLVED!  1 Saabers Like This Post!
Posted by skibumm100 [Email]  (#3255) [Profile/Gallery]
(more from skibumm100) on Tue, 3 Jan 2023 06:24:01
In Reply to: ECU compatibility-LONG, skibumm100 [Profile/Gallery]
, Fri, 2 Dec 2022 09:50:26
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Well this is a little embarrassing but I found the problem related to rough running on both of my 97 9000's, flakey tach movements, clock display blanking out, yada yada. As Simon pointed out, the Tech II gets its power from the OBD II plug and does NOT require external power. Somewhere in my original instructions for the Tech II I read that 12V power was supposed to be connected to the back of the OBD II plug for the Tech II. Maybe that's for earlier years, don't know. Pouring over the wiring diagrams for various system led me to Fuse 23. It supplies power to pin 16 of the OBD II plug under the column. I don't know what else it goes to but it was blown and was causing a myriad of seemingly unrelated issues. I have the whole dash torn apart and traced all of the different power sources to the power busses on the relay and fuse panel under the PS airbag. All of the power sources were reading correctly at the panel. In the process of troubleshooting this issue I took all of the grounds apart and cleaned them. I also took the ignition switch apart and used a points file to clean up the contacts. Simon was also correct in diagnosing a low voltage condition causing the fuel pump, A/C and fuel management relays to chatter. What I found that with a blown fuse 23, pin 16 of the OBD II plug still had about 3 volts on it. I'm not sure where that comes from as the wiring diagram shows it getting its power from the blown fuse 23. Must be the magic of solid state electronics. Anyhow, replacing the 5A fuse in slot 23 fixed both cars and restored them to normal running condition. It appears that by externally powering the OBD II plug on the Tech II I caused the fuse 23 to blow, which led to a bunch of weird electrical gremlins.
For the low temp issue I drained the coolant and changed the thermostat again and put a new one in. Even though the old one tested fine in a pot of water, it was not behaving correctly when in the car . Might have something to do with one side being pressurized when in a running car, don't know, grasping at straws. Turns out I had four new T-stats in various Saab parts boxes so I put a new one in. Also replaced the coolant temp sensor between cylinders 2 and 3 on the back. I had one in the box too, so while I had the system drained, I changed it. Pretty sure the old one is still good.
Thanks for your help Simon! Always a voice of reason and fountain of Saab knowledge.
posted by 165.225.220...
_______________________________________ long-time listener, first-time caller Saab glutton for punishment
, Fri, 2 Dec 2022 09:50:26, Tue, 3 Jan 2023 06:24:01 <-- Viewing This Message
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