From: John De Armond
Subject: Re: Loss of power
Date: Mon, 20 Dec 2004 22:57:24 -0500
On Mon, 20 Dec 2004 17:47:56 -0800, "Ben Hogland" <email@example.com>
>I had nearly the identical thing happen in my 2000 (Chevy) Tioga early
>last year. Lost all power, I pulled over and it was still idling fine..
>Decided to turn off engine, restarted about a minute later.. Nothing
>abnormal on the instrument cluster (no dummy lights lit). Started to
>drive again and worked just fine. I took it into the shop a week later
>and had them check it out.. They thought I was crazy. Said if there was
>a problem, the "service engine" light would be on. Hasn't been a problem
>since and that was more than a year ago.
Glad you didn't let that outfit work on your car because whomever told you
that didn't have a clue. The OBD specifically does NOT react to transient
events. If it did people would be lined up at dealers. Maybe 90% of what
the PCM does is complex diagnostics that try to separate transient but not
harmful malfunctions from things that matter.
You can prove it yourself. Go underhood and pick a sensor, any sensor.
With the engine running, pull apart the connector. No, it won't hurt
anything. The engine may or may not quit running but the MIL will NOT
come on. If the engine stays running and after a period of time, when the
PCM runs that particular non-continuous diagnostic, THEN the MIL light
will come on.
With an instantaneous loss of power like that, the first thing I'd do is
check the battery posts, particularly if you have those hideous side mount
things that hide corrosion. A bump can cause a corroded cable to break
contact. The alternator regulator, not being fast enough to react, will
allow the voltage to soar. The PCM will shut itself down to protect
itself from the high voltage. Meanwhile the jerking of the engine against
its mounts as the power abruptly cuts may make the cable make good contact
again. The PCM turns back on and away you go. I've seen this happen a