ECM reset

[Razor]

Having problems with ecm resetting under high rpms and high load..all data and info goes to zero when this occurs.Its like if ignition were to be cut off..but thats not the case.

Ignition and Battery wires confirmed to have power when this condition occurs at the ecm terminal.

With direct scan I can see all data going to zero and then coming back up.Have swapped ecms,plugs,wires,ground straps at engine,running out of ideas...

My next test today is a spare coilpack/ign module..but fearful thats not gonna fix it.

Any ideas would be appreciated

 

[dthrock]

Directscan

I had this exact same problem just after I had installed Directscan on my car. It would cut out like it completely lost power. What I found out was happening was the DS ribbon cable was picking up interference and causing the ecm to reset. I wrapped the ribbon cable in tin foil and problem was solved. Also make sure to check your other ecm wires for nicks and tape them up if you find any.

HTH

Dave

 

[ijames]

I had this problem too. It turned out to be a poor connection at the directscan cable to the ecm, where you clean the fingers. Obviously, make sure the fingers are really clean. Next, the connector goes on so far that sometimes it can short two traces where the fingers end and traces start. Also, on my ecm, the fingers aren't centered so when I put the connector on the contacts were overhanging the sides of the fingers and getting close to shorting to the adjacent finger. I had to file one side of the board to move the connector over so it was on center, and then carefully align it after plugging it in. I used the "Chu toothpick solution" to fix mine and two friends who had the first problem. Take a round toothpick, shave the sides a little if needed, and push it down to the bottom of the ds connector. That limits how far the connector can go onto the board and eliminated the problem. Kent recommended this once on the gnttype list and it works.

 

[Razor]

Ok...problem is this is happening without the direct scan plugged in..Thats why I plugged in the DS to see if it would give me any hints..

Could the ignition module cuase this or noise on the main lines from an alternator?

 

[ijames]

Okay, sure, shoot down my brilliant diagnosis . Hmm, you are sure about having power at the ecm connector on both wires when this happens? Is there any corrosion on the connectors? Pins look good on cable and ecm? Sounds like the ecm itself is the next step. So far as I know the only way to reset all the values to zero in the ecm is to pull the power or do something internal maybe (which is why we all suspected ds), since there is no external reset input. How did you monitor the power lines? Is it possible you missed a very short glitch? If you can swap ecms and it goes away then it has to be in the wiring, and most likely where the harness passes the headers and the fusible links go to the starter, and you're getting a brief short when the motor torques over.

 

[dthrock]

Do you leave the DS ribbon cable connected when not using it? As I mentioned, once I put tin foil on the ribbon cable it stopped. Never happened since.

Mine only happened at a wot run. On DS everything would go from normal value to 0 then immediately go back up to about where it had been. The engine would make a noise like it was coughing then take off again. Even if this isnt the problem shielding the ribbon cable wont hurt.

Dave

 

[Razor]

Carl,
Thanks for the replies...I'm having him drop the starter and pull the wire assembly out and inspect it.

I monitored the batt and ign lines using a test lite at the wires going into the ecm.And the lite didnt flinch when this occured.We were traveling 105 mph

Has done it with two different ecm's and different chips/calpaks.

With and without direct scan.All values on DS go straight to zero and the car dies,resumes,check engine lite comes on and goes off,no trouble codes.I can replicate the condition by turning the ignition switch off...

But these problems started after his starter took a ditch a couple months ago....

So last question..how many links are in the harness,what do they feed, and what values are they....Anyone have a diagram laying around.I'm really curious as to the interaction of these wires.Do any of these wires go to the ignition switch?

Thanks guys...My buddy Jimmy really appreciates it.

 

[ijames]

I can't remember how many fusible links there are for sure, it's either 3, 4, or 5 . I am sure that there are scans of the wiring diagrams in the tech area at www.gnttype.org. Also, I guess if the ECM loses it's ground it will act the same as losing power, except that there are a few different grounds. Anyway, check over the grounds on the back of the passenger head carefully, as well.