Chevy Colorado misfire

John Owner/Technician Massachusetts Posted   Latest  
Resolved
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2012 Chevrolet Colorado 2.9L (9 LLV) 4-spd (M30) — 1GCESBF94C8160390
P0351 — Ignition Coil "A" Primary Control Circuit/Open
Misfire

Car originally came in with misfire on cylinder one. (DTC P0351 - Ignition Coil 1 Control Circuit) Verified cylinder one was misfiring. Scoped ignition control and current ramped coils. Found IC 1 control signal breaking up. Tested signal by back probing pin one on ECM connector X2. Seemed like a slam dunk, installed and programmed brand new GM computer. SAME PROBLEM!! I dragged checked all pins on connector X2, no problems found. All other IC signals are good. Why just the one? What am I missing?

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Karl Diagnostician
Massachusetts
Karl
   

John Sure looks like a connection problem from image. Can you post psd file? Im sure you checked but did you check coil connector on the coil with the scope at all with same results? The only other thing that comes to mind would be ckp input problem if coil connection is good or coil power and ground issue. I think your signal should look the same from ecm no matter of power and ground at…

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Cody Diagnostician
Illinois
Cody
   

Have you tried swapping coils? Maybe a problem with the coil primary circuit? Edit; i looked at some service information and cleared up my misconception that it was a 2 wire coil. with that being said i probably would've came to a similar conclusion, although i would've likely swapped the coils first due to the rare possibility that somehow the module in the coil was causing a problem and…

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Don Owner/Technician
Texas
Don
 

Plug shorted? We had one that burned the electrode off and then shorted inside. Was on a Ford but it messed up the primary signal.

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Ray Diagnostician
Ontario
Ray
   

John, measure the coil ground voltage. this is from an 08 Volvo XC 90 4.4 CH A COP 6 ground wire with 3.5v CH D COP 6 amps

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Paul Owner/Technician
California
Paul
   

If it makes you feel any better, I would have figured the problem was the ECM as well. Given that it didn't fix the issue, I'd guess that the pin fit on connector X2 pin 1 is loose. Edits: I don't see how a coil could cause that. The voltage pattern is switched power from the ECM measured directly at the ECM. If the coil had low resistance or was shorting to ground, the amperage waveform would…

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Dan Owner/Technician
Texas
Dan
 

… I'd vote for a coil fault ( and do swaptronics, if possible)…what about doing a wire overlay…maybe power a sealed beam halogen bulb with the control ckt isolated on BOTH ends ?… Dan H.

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Richard Technician
Virginia
Richard
   

If that pattern repeats , then the signal from the pcm is being pulled down. The signal was never intended to be able to carry a load. Faulty coil. Similar to a 5 volt reference shorted to ground. HTH I bet if you put a microprobe on it , you will see an inverted V :)

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Paul Mechanic
Illinois
Paul
 

Disconnect coil and see if trigger cleans up. I would assume you'll already tried swapping coils before springing for a new pcm?

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John Owner/Technician
Massachusetts
John
 

First attempt, new Denso plug & coil. Second attempt swapped coils. Third try. ECM, In AM will try swapping coils and plugs one more time. Scope w coil unplugged and scope ground.I will see if I can grab a PSD file. Any chance a rub through would cause this. Not very repeatable but seems to happen more often in drive or reverse. Super erratic how often it happens too. Good times.

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Karl Diagnostician
Massachusetts
Karl
 

Yes either a loose connection or that #1 coil signal wire shorted(pulled low) would cause your scope pattern.

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Ray Diagnostician
Ontario
Ray
 

John, it looks like the low COP's primary coil winding's amperage draw is caused by a voltage drop in the power or the ground wires or the terminals to the primary winding. The low current draw thru the COP's primary winding is similar to low current draw thru corroded terminals to a dim headlight. Use wire piercing probes into the COP's B+ and the ground wire near the COP's connector and…

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Tom Diagnostician
Illinois
Tom
 

Just make your own ignition coil circuit control wire. Just for curiosity how look signal at ignition coil. Good luck

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Gilberto Diagnostician
Texas
Gilberto
 

How often is the problem duplicated ? wiggle test ? It being a Chevy I would lean towards loose pins . like Tom Wilks said make your own wire circuit to rule out wiring issue . Don't get down on your self we all get bit at some point when battling the Beast .

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Robert Technician
Michigan
Robert
 

weird graph to bad not spread out ,obviously coil is kicking when commanded …. I have no suggestion I'm sure you have done everything possible back probe everything right at the coil…. I wonder if that 1st post is correct a bad CKP trigger on 1 coil possible

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Richard Technician
New York
Richard
 

I agree with Karl, this looks like a faulty connection or damaged connector. As it pulls more amps the connection breaks. You could overlay a new wire to test.

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John Owner/Technician
Massachusetts
John
 

So….Put the scope away and went back to basics on this one. Problem was fairly intermittent, but when it did happen it would misfire for five to ten minutes. I swapped #1 and 2 coil while problem was happening (as many suggested} and issue went away. Hmmmm. Problem Has to be either a coil connector or wiring issue. Ran a test wire (once again many of you suggested) and the misfire has not…

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Ray Diagnostician
Ontario
Ray
 

Thanks for the update and which wire to the COP did you repair?

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John Owner/Technician
Massachusetts
John
 

IC1 From computer to coil.

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John Owner/Technician
Massachusetts
John Resolution
   

So I found the smallest rub through I have ever seen. It was at the main harness take out where it should have been secured by a bracket which was broken. I replaced one foot of wiring and secured the harness. Problem solved. Thanks again for all the help. John

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