Jon/Biff/others,
Thanks for the help. My guess is the o2 sensor is responsible. I know they
are well past they're lifecycle. My major question was if a failing o2
sensor could cause such dramatic driving problems. It looks like it can.
Biff - I can assure you that a 1997 Dak will display the 2-digit codes on
the digital readout (odometer) when using the key-on/off method. I've done
it several times.
And I wasn't totally clear on the check engine light on/off. The light will
turn on and then go off all while the truck is running. There's not really
a pattern to it and the light on doesn't always coincide with poor engine
performance. But like you said Biff, it's probably the fore sensor shorting
out whenever it feels like it which trips the light.
Thanks again for the help. I'll get some new sensors and go from there.
Thanks.
--Aaron--
From: "Biff Byrum" <bbyrum9@foothill.net>
Reply-To: dakota-truck@dakota-truck.net
To: <dakota-truck@dakota-truck.net>
Subject: DML: Re: Code 21 Help
Date: Wed, 7 Jun 2006 01:52:05 -0700
A few problems with what you said:
A: I have never heard of a '97 giving off OBDI codes.
B: Code 12 is not exactly common, it indicates loss of voltage to the PCM
within the last 50 key cycles.
C: You are a little over the recomended cycle life for an O2S. Even the four
wire models are only supposedly good for about 80K.
Your questions:
1: Yes, absolutely. I've had first-hand experience. It occured at the end
of January one year, and I had installed the new O2S at the end of the
previous September.
2: Bernd had stated that he felt the aft sensor could have a hand in making
the PCM do funny things, but you always look at the fore sensor first. The
aft sensor supposedly just measures Cat efficency, but, it's in the loop.
3: When the PCM detects a malfunction that calls for a hard set, it sets the
light. Whenever you turn off the ignition, and turn it back on again, if the
PCM no longer detects the same malfunction, why would it set the light
again?
4: Absolutely, anyone who says that the fuel that comes out of the nozzle is
always perfect, deserves to find out the truth the hard way , at someplace
like Harris Ranch on I5 in the middle of the San Joaquin Valley.
Bottom line: Your fore sensor is shorting out whenever it feels like it.
Think about it, if it's shorting out and returning well over 0.8 volts to
the PCM, how will the PCM react?? Simple, by leaning out the injector pulses
until it can get the value back down. But it can't, because it's not a true
value.Catch 22?? Biff Byrum .
.
.
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