closed vs open loop

Ed Wright · 06-07-2016, 02:24 PM

If wiggling the harness won't make it stumble, or die, try "the slap test". Take the computer out of it's mount, hold it in one have, and slap it with the other, while the engine is running. If it stumbles' misses, etc, you have a broken trace on the printed circuit board. Not uncommon at all.

Alan Roehrich · 06-07-2016, 06:22 PM

Take a plastic hammer (or small ball peen) and tap lightly but firmly on components such as ECM, MAF sensor, coils, module(s), relays, etc.

Check grounds and harness connections everywhere.

Also tap on and otherwise shake or vibrate the battery.

Ed Wright · 06-07-2016, 08:05 PM

GM recomends the "slap test", at least on my last trip to the GM Training center. May recomend mallets now, but I would be surprised.

Alan Roehrich · 06-07-2016, 10:40 PM

Quote:

Originally Posted by Ed Wright

GM recomends the "slap test", at least on my last trip to the GM Training center. May recomend mallets now, but I would be surprised.

The slap test works okay, on the ECM. The right hammer tap (and no, I'm not advocating beating it to death) will often expose a lot of components that have an internal fault, due to cracked boards, bad solder joints, loose pin fit, and various other "intermittents", especially those that show up on rough road, or under various sharp maneuvers.

Patric Fox · 06-11-2016, 05:28 PM

I was working on a Ford a few years ago which was acting the same, the DPFE valve would short and loose the 5V reference to the other sensors, causing it to stall. No codes either. Unplug it and try.

06-07-2016, 02:24 PM	#1
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: closed vs open loop If wiggling the harness won't make it stumble, or die, try "the slap test". Take the computer out of it's mount, hold it in one have, and slap it with the other, while the engine is running. If it stumbles' misses, etc, you have a broken trace on the printed circuit board. Not uncommon at all. __________________ Ed Wright 4156 SS/JA

06-07-2016, 06:22 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,116 Likes: 1,573 Liked 1,830 Times in 415 Posts	Re: closed vs open loop Take a plastic hammer (or small ball peen) and tap lightly but firmly on components such as ECM, MAF sensor, coils, module(s), relays, etc. Check grounds and harness connections everywhere. Also tap on and otherwise shake or vibrate the battery. __________________ Alan Roehrich 212A G/S

06-07-2016, 08:05 PM	#3
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: closed vs open loop GM recomends the "slap test", at least on my last trip to the GM Training center. May recomend mallets now, but I would be surprised. __________________ Ed Wright 4156 SS/JA

06-11-2016, 05:28 PM	#5
Patric Fox Member Join Date: Jul 2007 Location: Pottstown,Pa. Posts: 121 Likes: 24 Liked 11 Times in 8 Posts	Re: closed vs open loop I was working on a Ford a few years ago which was acting the same, the DPFE valve would short and loose the 5V reference to the other sensors, causing it to stall. No codes either. Unplug it and try.

Thread Tools
Show Printable Version Email this Page
Display Modes
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode