no fire at the coils on my envoy


Asked by May 04, 2015 at 10:53 PM about the 2005 GMC Envoy XL Denali 4WD

Question type: Maintenance & Repair

my envoy will not start from time to time I check and has no fire at coil packs, a hot 12 volts with ign on then all the sudden it gets fire and starts have replaced ign switch,map sensor,oilpressure switch.this thing will die and wont start for an hour then fir e up and go.has 12 volts at crankshaft sensor on ign but not at coils.bumfuzzled

17 Answers


Any codes in the system? My guess is the crank sensor,but run a code check first.


it throws no codes has four wires at coil pac ground is good the pink or red that should have voltage with key in on pos has no fire then wait and will have voltage then start have replaced ign switch with ac delco will be driving about 30 min then dies no fire wait and starts back up have replaced pcm with used one and had flashed still doing same wondered if something getting hot and breaking down then cools and lets voltage carry until it gets hot will ck crank sensor ,but not sure why no fire at coilk pac with key on


You might also want to check the ECM relay, it might be clicking but not making contact, I believe it is number 5 in the power box.


I switched all relays around ,ran today for about hour and half died then no constant power to coils, waited about half hour and started with power back at coils,still wont throw a code just dies


I still think it is the crank sensor.


will the crank sensor cut off supply constant to the coil it has 4 wires the pink wire should have constant power to start,will crank sensor cut that power? soon as cools off it gets power and starts

1 people found this helpful.

Got to: the-crank-sensor-1 Read the whole chapter.


I looked on troubleshoot how to test cop coils test 3 according to that I have a power circuit problem but didn't find a fix thanks for lead


Do you have a scan tool that can do "live data"?

1 people found this helpful.

I had this scan done today and died while they were doing it,have been told its a power block under the fuse box?

2 people found this helpful.

Im workin on the same problem and I beleve its the fuse box the powertrain relay gets hot and it wont start till it cools off .... the fuse box Gets hot losses the ground ... start it run it till it gets hot then turn it off if it dont start again swap the powertrain relay with the starter relay and it should start if it does check the wires going into the bottom of the fuse box at the powertrain module if there good replace the box

3 people found this helpful.

I bet ur getting throttle body codes and ignition codes also if so we already replaced all that stuff and the same thing untill we put it on our scanner and its not a cheap one thats how I found it

1 people found this helpful.

Did you figure out your problem Ricky ? Mines doing the same thing..

2 people found this helpful.

I have changed almost everything from crankshaft, battery, ign switch, all relays, throttle body, and mine keeps dying. I can't drive out 15 miles before it dies.. Im going to change fuse block today to see if it fixes problem

I had found a lot of people having problems like this I found that the computer wires was lose on the side where 3 plugs go in left side intake wiggle them eng run great hope this helps

The black wire going into the coil rail should be ground. I had the same problem not spark all fusses were good I grounded the black wire and it started right up. Not good to hook up to ground but what ever is causing that wire to loos ground is the problem.

My sister was having this problem had her computer reset, no problem in months

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