Date: Sat, 3 Aug 2002 13:31:05 +0100 From: "A&M" <andymegnopsameycheese.freeserve.co.uk.no_spam> Subject: Re: strange ECU or o2 sensor problem
try here instead much more likely to get your technical questions answered http://saabnet.com/tsn/bb/9000/ andy "Dave Wysocki" <MAPSdwysockiONnopsampc.com> wrote in message news:3d485176$0$1423$272ea4a1nopsam.execpc.com... > I've had an intermittent problem with my '93 9000 CSE T (5spd, w/TCS), > where within a few days after resetting any engine codes (or > disconnecting the battery), the check engine light will come on, with a > flash code of 6 (o2 sensor error), or occasionally 7 (fuel-air mixture > error). The local Saab dealer agrees that the problem is not with the > o2 sensor itself (I've tried 3 in the last year), but says that there is > a 450mV reference signal missing from the ECU to the o2 sensor, and that > this reference level "starts the sensor". My understanding of the Bosch > 3 wire sensors is that they are output only devices (except for the > heating element), and although I don't have a schematic of the ECU > itself, it would make sense for the ECU software to use a software value > of 450mV until the o2 sensor is up to operating temperature, but it > wouldn't make a lot of sense to have a hardware reference voltage put on > the o2 input to the ECU. When the system is functioning correctly, the > o2 signal toggles from about 0.2VDC - 0.8VDC, but when the check engine > light comes on, it stays at about 0.8VDC. > > Thanks in advance for any suggestions. > > Dave Wysocki > '93 9000 CSE T, 212K miles > '84 900 S, 420K miles, RIP