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Of course, it happened when my wife was driving. She said "The car would buck and stall, but always restarted, but as soon as I tried to go it would stall again"
What I found: Car starts up fine and all warning/test lights go out. Press slowly on gas pedal - no problem. Press (or release) pedal quickly and she stalls - but the TCS light comes on a second before stall.
Two problems - 1) car goes into LHM and 2) Car stalls in LHM
I check and clean all connections - no change - so I need to fix problem 2 at the scene to drive it home. I adjust the LHM cable so she doesn't stall. Restart, all is normal. Press gas pedal quickly and the TCS light comes on, she goes into LHM and idles.
After reading many of the TCS postings here it seems to me that it must be the Accelerator Pedal Sensor because it only happens with abrupt movement of the pedal and it happens whether the car is stationary (in neutral) or moving in any gear.
I take the car to an independent that has the Tech2 machine to read the codes. The car has four codes - one is "Permanent" (E7590) and three are "Intermittent" (77594, 25251 and 25721)
They replace the Bleeder Valve ($86) and the Bypass Valve ($55), recalibrate and road test. TCS light comes on and she goes into LHM. Pull the codes again, and they’re the same four. They replace the Pedal Sensor ($170), recalibrate and road test. All OK. Those parts, three hours labor, five gold terminal ends - $508.50
When I get home I check the codes in the Saab 9000 M1992 2:5 Traction Control System book and they are as follows:
E7590 – Safety System Activated – 1. If other fault codes occur at the same time, deal with those first. 2. Clear the fault code and test drive the car to see if the fault code is regenerated. 3 Connect a vacuum gauge…
77594 – ECU fault: safety switch 31 – If another fault code exists which begins with a 2, 3, 4, or a 5 (2XXXX, 3XXXX, 4XXXX, 5XXXX) investigate that fault first. Clear the fault code and test-drive the car to see if the fault code is regenerated. If so, try a known good ECU.
25251 – Pedal potentiometer signal faulty or missing – Test resistance values. If resistance values are incorrect replace the pedal potentiometer.
25721 - Pedal potentiometer safety-switch signal faulty or missing – Before starting the test procedure, check that movement of the pedal is not hampered, for instance, by the floor mat. Test resistance values. If resistance values are incorrect replace the pedal potentiometer
It’s quite clear that the two problem generated the two important code – that is 25251 caused the car to go into LHM and 25721 caused it to stall in LHM - and the other codes did not regenerate after the pedal pot was replaced.
So I asked them why they changed the Bleeder and Bypass valves even though the procedures in the book didn't say to do so and they replied “They’re the cheapest parts and they usually fix the problem.”
They also noted that the “Throttle Housing looks original, may need in future”
I hope this can help someone!! If you need the Pedal Potentiometer resistance tests and don’t have the TCS book (but everyone with TCS should have the book!!), drop me an e-mail and I’ll give you the details from mine – just remember it’s the book for model year 1992! gksimms@earthlink.net
Utan Tak
posted by 63.214.19...
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