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Random stalling

The problem with truck is multiple issues. I found and re replaced a factory splice going to blue ecm plug. Then with a pmd mounted at plug by block. No start, I removed optical sensor and nothing . I removed the ait and maf plugs. It acts like it reset itself and wants to run off crank values. I plugged everything back in and it runs as it should. I still need to learn to trust it. I’m not big on walking. Update later.
 
So when you unplug either the CPS or OS it will take ALOT of cranking to get it to start. When it does it will be in limp mode but should run nice and smooth. If it fails to start with the OS unplugged it tells you the either the CPS is bad or the wiring associated with it is bad. Same goes for when the CPS is unplugged. You're basically testing the sensor that is still plugged in.
 
ak diesel driver said:
So when you unplug either the CPS or OS it will take ALOT of cranking to get it to start. When it does it will be in limp mode but should run nice and smooth. If it fails to start with the OS unplugged it tells you the either the CPS is bad or the wiring associated with it is bad. Same goes for when the CPS is unplugged. You're basically testing the sensor that is still plugged in.
Click to expand...
With a known good pmd plugged on bumper/heatsink. I have to unplug easy to access sensors along with optical sensor. It will start and be a little smoky. Then I plug all the sensors in and it runs properly. I think the next ride I will bring my Polaris atv and ramps. Hopefully I can move on to new carpet and headliner.
 
What intent did I miss AK. Do you think optical sensor is bad? I am checking the wiring and signal today. I ferreted out what I thought was a working PMD. I believe an issue still exists. The IP is new from GM. What did I miss. Sometimes I can’t see the forest because of the trees.
 
hookedup50 said:
With OS unplugged it starts, but anything but smooth, I am glad cps works though, as I go through lots of those over the years.
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Something is not right if You arr going through a lot of those.
I had to replace one in about six years and that one was transferred to the new engine.
I’m confident it will perform just fine in this engine too.
 
MrMarty51 said:
Something is not right if You arr going through a lot of those.
I had to replace one in about six years and that one was transferred to the new engine.
I’m confident it will perform just fine in this engine too.
Click to expand...
A lot might be too strong an expression. It’s the only sensor that goes bad on truck. I’ve probably changed it twice since 2012. It’s the one code the ecm throws, that is trusted.
 
Today the belt and tensioner are getting changed. The belt has cracking in the v grooves and the tensioner is out of spec. The spring is worn out, and I think it is chinezeum and got a gm one off parts shelf.
 
Runs with cps off now, smoking but runs. Clears up upon adding plug. The tensioner was badly needed and was slipping. It was loose enough to rub material off the flat of the belt. Everything new that rotates, including Leroy billet pulley and fluiddampner.. Took a 20 mile jaunt, no fishbiting, just smooth.
 
So it sounds like in post 66 you unplugged multiple things. When doing the CPS/OS test everything else stays plugged in. You don't unplug wit the engine running either. The whole point is to isolate just that one sensor and then try to start it . In limp mode it uses a basic tune. (A getcha home safe tune). If it doesn't run smoothly then that indicates there's an issue.
Maybe I'm misreading your post ....
 
Sorry for confusion. With a new flight system pmd, it runs now isolating either. My known good pmds that were failed and one failing. The problem with a known good pmd, is that it’s good till it isn’t. I did that wacky stuff to weed out the failing pmd. I got a lot of years out of those flight system pair. The problem with owning a truck so long is that new part you changed last week was a dozen years ago, if I dont check the log of receipts.
 
By the way, thanks to everyone who have helped me over the years. I think I can finish stitch welding lower cab and rockers. I refuse to-weld on something that won’t run. Im probably gonna trial this to Toronto 800M round trip. If it runs well on next trip about 60 miles, with no hiccups, Im sending it.
 
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