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 .
----- Original Message -----
From: "A. S." <adakota4x4@hotmail.com>
To: <dakota-truck@dakota-truck.net>
Sent: Tuesday, June 06, 2006 3:12 PM
Subject: DML: Code 21 Help
>
> Truck:
> 1997 Dakota 3.9 V6 Auto 152K miles
>
> Problem:
> Truck starts and runs fine, but 2 or 3 miles down the road it begins to
> sputter and lose power. It almosts acts as if it's not getting gas and
> wants to die. Turning the truck off and restarting fixes the problem and
> then the truck can be driven 50+ more miles without problem (this has
> happened 3 or 4 times now).
>
> The check engine light comes on sometimes but will go off by itself. I've
> checked the codes and get the following: 12, 21, 55. I've know that the
12
> and 55 are common and the 21 is related to the o2 sensor.
>
> The catalytic converter recently began rattling. About a week after the
> rattle began, the check engine light came on and the troubles began. The
> cat. and muffler have since been replaced, but the problems continue.
>
> Nothing else has been replaced (o2 sensors are both original).
>
> No change in fuel mileage or performace other than the symptoms mentioned
> above.
>
> Questions:
> 1. Can a bad o2 sensor cause these symptoms (stutter, no power, kill
> engine)?
>
> 2. Code 21 relates to both sensors.....which one is more prone to dieing?
>
> 3. Is it normal for the check engine light to come on and off by itself (I
always thought it needed to be cleared once on)?
>
> 4. Could I have a fuel problem that just happened to show up with a bad o2
sensor but won't trip a specific code?
>
> Thanks for the help.
> --Aaron--
.
.
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