ECM Reset

m3x1c0

Bad luck Buick
Hello all. Wanted to see if any of you had seen this problem as I have seen it on my own personal car as well as several customer cars. Check out this datalog below. As you can see there is a single frame where the ECM resets itself. You see RPM drop to nothing, and the same with the TPS and Battery voltage. However the boost, which is measured through the powerlogger input rather than the ECM does not have a sudden drop to zero.

I have fought a similar problem to this in my personal car for years. Every time I find a bad ground, corroded connection I think "AHA! I've found it" only for the same thing to happen randomly weeks or months later. As I mentioned before I have seen this in other cars but most often the answer lies in the grounds at the back of the head, or the fusible links by the starter. With these cars the problem will occur randomly and go away for days at a time. However, in this customers car I've seen this with every single run on the dyno.

Talked with the guru Bob Bailey last night and was told that a missing crank pulse will do exactly this. Of course I found nothing wrong with the crank sensor but did find a tiny bit of silicon that had dried on the tip of a window in the reluctor ring. After fixing that we ran out of time for the night.

Anyways just wanted to post this up as it seems to be a common problem. Will post up the results of our dyno runs today and when we find the solution will post it up.

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TurboBuRick

Moderator
Staff member
X3 what plugs?

Also pull the powerlogger off the ecm and clean leads. Use some emery cloth or a small wire toothbrush. Make sure the coating is off all the leads.

Post the file too so we can get a better look.
 

dynoman

Well-Known Member
Had it happen to me with non resistor plugs and right around 15 psi boost . Those plugs had less than 20 miles on them when I changed them back to resistors .
 

TurboBob

Resident mad scientist
Staff member
I agree on the spark plug question, I have seen non-resistor plugs cause issues with lots of things, not just a PL or ECM.

I sent you a link to some contact conditioner I use with the PLs, I think it helps with this sort of thing.

Make sure there is no pressure on the PL, that can cause contact issues. I sometimes put an extra layer of double-sided tape on the PL so it gets sandwiched more tightly.

Also, the new PLs (starting a few years ago) have a nylon stud that provides a more robust mount for the unit.

It could still be the crank sensor, or something else resetting the ECM. Post a logfile.

Bob
 
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