Re: Base boost tribulations - Saab 9000 Bulletin Board - Saabnet.com
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Re: Base boost tribulations
Posted by JimO (more from JimO) on Fri, 14 Nov 2008 06:05:44
In Reply to: Base boost tribulations, Steve C., Thu, 13 Nov 2008 10:17:52
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I am chasing the exact same problem you are having. '93 CSET. I have two ECUs stuck in base boost. One I replaced the three MOSFETS (BPC had shorted and took out Fuse 5) and still am stuck on base boost. The other ECU was in there for recent BPC fail (one of the coils failed open) and the MOSFETS appear to be fine. Same result - stuck on base boost.
I am starting to trace the circuit back and have some suspicion that possibly the HC123A (Monostable Multivibrator) that drives the MOSFETS has failed. There is a 2.2K resistor in series with the MOSFET Gate that should current protect this device. Reference the document in this link for some good information: http://en.wikipedia.org/wiki/Trionic_T5.5. Open the document at the bottom of the link (pages 37, 140). I am considering replacing this device also and see if that solves the problem.
I am reluctant to drop another $150 for a used ECU and would rather try to figure out what is really causing this problem. Stay in touch.
posted by 130.76.32...
Posts in this Thread:
- Base boost tribulations, Steve C., Thu, 13 Nov 2008 10:17:52
- Re: Base boost tribulations, Jack, Thu, 25 Mar 2021 22:44:54
- Re: Base boost tribulations, JimO, Fri, 14 Nov 2008 06:05:44 <-- Viewing This Message
- Re: Base boost tribulations BPC valve, BobS, Thu, 13 Nov 2008 15:07:10
- It's not the wire that goes to pin 2, Bill Homer , Thu, 13 Nov 2008 11:13:21
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