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, Sun, 27 Oct 2002 22:57:05
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For a simple O2 sensor fault situtation, new sensors might let the system adapt and be happy in a short while. The CEL would still persist for a few days, but they would clear that fault code in a routine fashion.
With the wrong sensors, or the sensors wired wrong, the ECU could have gone into Limp Home mode when it became impossible to work normally. This 'failure mode' can be persistant. I had a split hose to my map, and the O2 sensor ground was also found to be resistive. I am glad that I have only one sensor! So after the dealer set things straight and cleared the codes and did whatever resets that the TecH-II provides for, the engine still would not run well. Eventually they did remove power from the ECU and that got it workiing normally. So it appears that the ECU can get stuck in a failure mode or limp home mode. But I expect that that is a rare issue. And the 1995 T5 might be a bit primitive compared to later years and the ODB-II versions. But not of this really applies to your Motronic ECU for your V6 engine.
My question from the previous post, was whether one of the wires on a 4 wire sensor is a signal ground. If this was done, then the whole issue of ground resistance in the exhaust system would go away. But if the 4 wire sensors still ground the signal via the exhaust, then you don't know if you have bad sensors or a ground problem. When someone states that they have more than one sensor going bad at once, I start to think about a ground problem affecting multiple sensors.
(Note that the heater current returns on its own ground side wire, because they cannot 'sink' the heater current through the exhaust system, as any resistance in the exhaust system would then shift the ground reference for the sensor!)
posted by 207.43.195...
, Sun, 27 Oct 2002 12:19:53, Sun, 27 Oct 2002 22:57:05
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