SUV sat for a weekend, come early morning Monday to go to work. Started up just fine came to temp, windows defrosted. I am about 1/2 mile from home and it goes almost dead, barely running and then dies. Try to restart and it dies almost immediately. Finally after about 10 tries it runs rough enough for me to make it home (full throttle never gets above 1200 rpms). And it hasnt started back since. I troubleshot (is that a word?)to the best of my ability. Fuel pump is working, can consistently produce 62psi on the fuel rail after pressure release. No obstructions in air delivery. Get to spark and there is none both banks. Coils are all getting power with switch on and cranking. I surely thought the Crank PS went sour and fought that for about 2 hours with my gorilla hands in that tight area. Still no spark. Not sure where to go from this point. Any advice would be much appreciated. Thanks!
NEED HELP 06 Envoy Denali 5.3 No Spark
- Thread starter HardTimes
- Start date
Mooseman
Moderator
Is ground getting to the coils? This guy had that problem.
What about the trigger signals? Any codes?
What about the trigger signals? Any codes?
Mooseman
Moderator
m.mcmillen
Member
If you have a scan tool that can read live data, check the engine RPM while cranking. If it isn't registering, you've got a problem with the crankshaft sensor.
I changed the crankshaft sensor on a 5.3 once and it didn't run afterwards. I found that there was a rust buildup around where the sensor went in and was keeping it from seating all the way. I cleaned it up and the truck ran perfect.
I changed the crankshaft sensor on a 5.3 once and it didn't run afterwards. I found that there was a rust buildup around where the sensor went in and was keeping it from seating all the way. I cleaned it up and the truck ran perfect.
Mooseman
Moderator
Maybe the cam sensor.
BTW, is the security light on by any chance?
Beyond this, you would need a scope and/or high end scanner like a Verus or Tech 2 to check the actual RPM signal.
This video shows the steps for checking signals and other stuff you've already checked. It's long so speeding it to 1.5x helps. He's one of the better Youtubers out there.
BTW, is the security light on by any chance?
Beyond this, you would need a scope and/or high end scanner like a Verus or Tech 2 to check the actual RPM signal.
This video shows the steps for checking signals and other stuff you've already checked. It's long so speeding it to 1.5x helps. He's one of the better Youtubers out there.
Was able to use my coworkers Autel Maxisys unit today after work. I ran live data. 5v reference was good. While cranking the RPM would register no more than 48 intermittently. Drilled down to the CKP and it was the same. Not sure what this should read normally while cranking. I used a feature of the scan tool to run a scan across all modules. The driver door module showed 1 fault and it was U1017. All google searches mention CKP Loss of communication with PCM. But why is that in the driver door module?
Mooseman
Moderator
Loss of communications happen on a regular basis and are kept in history for a long time. I wouldn't worry about it especially since it's for the door module.
Maverick6587
Member
Maybe a bad ground at the park/neutral safety switch or a bad park/neutral safety switch? Or would the park/neutral sensor not allow it to crank at all?
I would check fuses #56 and #31, those are the fuses for the ignition coils. Ground #109 is the ground for all of the ignition coils, screenshot below. I would clean all of those grounds and use dialectic grease on them after you clean them. I have had a bad engine ground before and it looked perfectly clean.
You could also check for continuity at at the pcm for the ignition coils as well as see if they are getting a control signal coming from the PCM. Wires 1, 30, 32, 13, 23, 31, 22, and 12 are the control wires coming from the PCM, screenshot below.
I would check fuses #56 and #31, those are the fuses for the ignition coils. Ground #109 is the ground for all of the ignition coils, screenshot below. I would clean all of those grounds and use dialectic grease on them after you clean them. I have had a bad engine ground before and it looked perfectly clean.
You could also check for continuity at at the pcm for the ignition coils as well as see if they are getting a control signal coming from the PCM. Wires 1, 30, 32, 13, 23, 31, 22, and 12 are the control wires coming from the PCM, screenshot below.
While you investigate the Electrical Supply hardware for valid Spark Plug Ignition, it might be worth moving to the front of the Engine and after pulling and changing the Air Filter if Dirty or contaminated with too much Oil if it is a K&N Aftermarket version, take a VERY close look at the MAF - IAT Sensor and along the length of its Harness and Pin Connectors for any Broken Wires. Then use some CRC Lectro-Motive Electrical Circuit Spray Cleaner to un-plug, clean out the said connectors and when completely Dry... carefully re-insert them:
As well ... using only the CRC MAF Sensor Spray Solvent, thoroughly clean the Grid and Internal Sensing Wires of any Dirt or Debris. In many cases... even with sufficient Air, sufficient Fuel and the presence of a Powerful and accurately distributed Spark through the Bank 1 and Bank 2 Coil Packs... things can go sideways with the PCM NOT knowing when to 'touch off the cannons':
If the MAF-IAT Sensor suddenly loses its ability to WEIGH THE INCOMING AIR because it has a Dirty set of Sensor Wires... OR.... if the MAF-IAT Sensor suffers from any intermittent breaks in the passage of MAF signals along its Harness signals due to Broken Wires or loose wire pins inside of the Connectors... to and from the PCM... then the Engine can suddenly Stumble and-or Fail to Run.
Amazon.com: CRC 05018 Lectra-Motive Electric Parts Cleaner - 19 Wt Oz.: Sports & Outdoors
Buy CRC 05018 Lectra-Motive Electric Parts Cleaner - 19 Wt Oz.: Electrical Cleaners - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
As well ... using only the CRC MAF Sensor Spray Solvent, thoroughly clean the Grid and Internal Sensing Wires of any Dirt or Debris. In many cases... even with sufficient Air, sufficient Fuel and the presence of a Powerful and accurately distributed Spark through the Bank 1 and Bank 2 Coil Packs... things can go sideways with the PCM NOT knowing when to 'touch off the cannons':
Amazon.com: CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz.: Sports & Outdoors
Buy CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz.: Collision Repair Sets - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
If the MAF-IAT Sensor suddenly loses its ability to WEIGH THE INCOMING AIR because it has a Dirty set of Sensor Wires... OR.... if the MAF-IAT Sensor suffers from any intermittent breaks in the passage of MAF signals along its Harness signals due to Broken Wires or loose wire pins inside of the Connectors... to and from the PCM... then the Engine can suddenly Stumble and-or Fail to Run.
Last edited:
Beacon
Member
How did you check for spark? Did you use an old plug? Or light, similar to this?
Amazon.com: ABN Inline Spark Plug Tester – Straight Boot Ignition Test Light 2pk for Small Engine, Car, Lawn Mower, Chainsaw: Automotive
Buy ABN Inline Spark Plug Tester – Straight Boot Ignition Test Light 2pk for Small Engine, Car, Lawn Mower, Chainsaw: Spark Plug & Ignition Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
Beacon
Member
Correct. No pulse from computer while starting. Also checked the grounds and followed a video up above grounding them to the battery to see if that would work.
Mooseman
Moderator
I would concentrate on this. It's getting a signal but it should be consistent. If you rewatch the video I posted from South Main Auto, there was a signal but the CKP was bad as it was not pulling the signal down to 0v.
When you went in there, did you actually replace the CKP? (your first post doesn't specifically say so) If you did, what brand? Sometimes, only ACDelco parts work with electronics. If you do go back in there, check the reluctor wheel inside the hole with a plastic tool to be sure it's still solid to the crankshaft. There has been one instance of this wheel breaking off. While looking in the hole, turn the crank and watch the teeth to be sure none are broken.