Clearing Engine Codes and Battery fitment 3.3L

[Cressida]

Does anyone know how you can clear any stored ECM / Engine codes other than disconnecting and reconnecting the battery ? I thought that pulling the ECM fuse would do the trick but it does not on my 1993 Ciera 3300 3.3L.

I have a group size 78 battery installed and getting to that negative side post cable is a real pain! I was always taught to remove the negative cable first, but since the positive cable seems easier to access on my Ciera would I create any problems just disconnecting the positive cable to clear codes and leaving the negative alone ?

Also, have most of you been running a group size 78 battery or 75, or what ? I'm probably going to need one sometime later this year and may go for a smaller size just to give me more clearance.

[tlc1976]

I just disconnect the battery for a few minutes to clear codes.

Due to lack of room, I usually just disconnect the positive. There is no difference in the end, except if you touch the positive post to the body you’ll get a spark.

I always use the 75 series battery. That’s cramped enough as it is. I couldn’t imagine fitting a 78 series in there.

[Cressida]

Thanks for those helpful comments tlc1976. I disconnected the positive terminal and indeed it was much, much easier to clear the codes that way!

I'll document for myself and others that I was working on a code 34 that had showed up. It turned out to be a bad MAS (mass airflow sensor). After clearing the code and restarting the engine the "service engine light" would come back on after only 4 seconds and set the same code 34 again. That was showing that the ECM was getting no reading from the MAS. I removed and cleaned the old MAS with no change - the old MAS looked good and normal. I then checked the ohms reading b/t pins B+C on the old sensor and it showed none or open. On the replacement sensor I got a reading around 518 mohms b/t B+C.

On the wiring connector side (part that plugs into the MAS) if all is good; one is looking for a reading of ~ 5v (4 to 6v) b/t pin A and a ground, and battery voltage should show b/t B+C. That reading is taken with the key turned to the on position but the engine is not started or running.