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Dan M
Dodge Dakota
JOIN HERE
1/05/2006
04:21:44
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 Subject: code 25 and code 21
IP: Logged
Message:
25 is IAC motor circuits - open or shorted condition
21 is O2 sensor voltage at center - neither rich nor lean OR O2 sensor voltage high - O2 sensor input voltage maintained above normal operating range. O2 sensor was replaced a little over a year ago but to be sure it was good, i replaced it again.
truck backfires. Also I noticed that my engine temp guage sometimes does not work (never moves off cold) or bounces around. I just replaced the coolant temp sensor a couple of weeks ago.
I pulled pcm connector and checked all 4 wires going to the IAC and all tested fine for continuity and tested nearly the same for resistance.
I recently found 1 of the 2 ground wires at pcm connector was loose. Since fixing that, i have had these 2 codes and backfiring.
I checked wiring diagrams and see that there is another wire that is the sensor ground that all sensors use. The coolant temp sensor, iac , o2 , and more use this same sensor ground (pin 4 on 60 pin pcm.
Truck will run a short time (probably until reached normal operating temp) then the check engine light comes on, it is IAC code 25. Then minutes after than the O2 sensor code 21 is thrown in addition.
Could it be that this ground wiring is bad/flakey ?
I am planning on buying a scan tool next week, however I can't really wait that long to resolve this issue.
- Dan M
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Dan M
Dodge Dakota
JOIN HERE
1/05/2006
05:48:42
| RE: code 25 and code 21
IP: Logged
Message:
a few other notes
new IAC, replaced it as a precaution to last issue I had with backfiring (final resolution was coolant temp sensor). There is a long post about this.
Put old IAC back on, same issue.
drove to work this morning, only code 25 was logged (IAC motor).
If the coolant temp sensor is bad, that is 3 in about 5 months. First one I bought at autozone, it worked fine for 4 months. When it failed i bought one at advance as the autozone one only had 3 month warranty. The advance one has 1 year so i can replace it under warranty.
95 3.9L 4x4 auto.
- Dan M
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?
Dodge Dakota
JOIN HERE
1/05/2006
09:20:33
| RE: code 25 and code 21
IP: Logged
Message:
Have you checked that infamous splice under
the underhood fusebox ?
Also - clean and tighten all chassis grounds you can find !
Including battery posts/terminals/connectors..
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Dan M
Dodge Dakota
JOIN HERE
1/05/2006
11:21:25
| RE: code 25 and code 21
IP: Logged
Message:
yes, that splice was redone some months ago.
The code 25/21 did not start until after I removed the PCM connector to test/fix my lose ground, pin 11 and 12 are ground. pin 4 is sensor ground.
I would think that if the sensor ground were bad other sensors would be showing bad??
- Dan M
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