The decisin for the ECU to attempt closed loop operation is based on coolant temparature, time engine running, and throttle switch/engine rpm. The signal at the O2 sensor input will effect what the ECU tries to do in closed loop operation. Dennis
>From: Mike Elliott <camping.elliott@GMAIL.COM> >Reply-To: Mike Elliott <camping.elliott@GMAIL.COM> >To: vanagon@GERRY.VANAGON.COM >Subject: Re: Heh -- I'm such a ninnyhammer >Date: Mon, 4 Aug 2008 07:16:00 -0700 > >Some comments to the below: > >>>That said, your situation with disconnecting the O2 sensor instead of the >>>gauge and the resulting response tells me that the gauge is a problem in >>>itself. >> >>Only if disconnecting the gauge makes the symptoms disappear... > >That will be tested today. Yesterday's conditions were: O2 sensor >disconnected from ECU input and meter input. Meter input and ECU input >still connected together, meter sat steady at midscale. Unless, as was >mentioned, the signal line had a lot of high frequency noise on it that >the meter could not display. > ><snip> > >> >>True -- although Mike said that the meter stayed centered, suggesting >>that the ECU was back in open-loop mode? > >I don't see how that indicates the ECU was in open loop, only that the >bias voltage at the ECU input did not change -- right? Pin 5 (O2 sensor >signal) is just a high-impedance input, yes? > >Possibly useful would be to disconnect the sensor signal from the ECU >input and connect it to the meter to monitor what the engine is doing when >the ECU can't see the sensor. David said something about biasing the >sensor with a half-meg resistor? > >-- >Mike Elliott |
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