cold start, open loop
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cold start, open loop What does the pcm use to determine fuel mixture when it's cold and the o2's haven't warmed up yet?
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Re: cold start, open loop Basically the same things it uses in closed loop (MAP, MAF, TPS, etc), except there's no feedback from the O2 sensors for the computer to make fueling changes.
My car runs in constant open loop and never goes to closed loop. No O2 sensors on my car at all.
My car runs in constant open loop and never goes to closed loop. No O2 sensors on my car at all.
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Re: cold start, open loop Ok. Second question. How do you interpert the MAP sensor? Manifold Absolute Pressure right? That's in reference to what? 0 vaccum?
Re: cold start, open loop The PCM waits for the ECT to reach a predetermined temp. When it does you go into closed loop. Until that happen the PCM has been given DEFAULT VALUES that it pretends are correct until the water warms up. Until that happens the PCM ignores all the sensors values except the ECT. The GM engineers have written a software table that contain the defaults. If a vehicle doesn't NOT go into CLOSED LOOP you have a real problem because the PCM is ignoring ALL your sensor inputs ALL the time. That ain't good. You need to check that out. Your vehicle could be way out of tune and you wouldn't even know it unless a DTC got set.
