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No Spark From Coil?!?!

jessb_55

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jessb_55 New Member

jessb_55

Posted
Posted

I have a 97 1500 with a 5.7l and recently it started running
rough under load, but idling fine. I parked it for the night and the next
morning it then wouldn’t start. Up until that morning I hadn’t been having any
trouble with it not starting.



I hooked up my scanner and it was throwing a P0340 and P0341
codes I looked up the codes and then proceeded to head to O’Reilly and pickup a
new crankshaft sensor.



I put the new crankshaft sensor in and it still wouldn’t
start, I then proceeded to put the old one back in and it still wouldn’t start.



I then noticed that inside the crankshaft sensor box that
there was a sheet of paper that said that the new sensor would need to be “relearned”
with a scan tool. I checked my service
manual and it didn’t mention that and then called to Stealerships and both of
them said that wasn’t the case as far as they knew. I also read somewhere else as well that even if the Crankshaft sensor was bad
that the truck would still run.



I then proceeded to look into the troublecodes more and then
realized that I read the codes wrong and that the codes actually pertained to
the Camshaft sensor NOT the crankshaft sensor ;)



I then decided to replace the Camshaft sensor, distributor
cap and the rotor. Still wouldn’t start!



I also know that the crankshaft itself isn’t broken as I had
to put a wrench on it to install the sensor and the distributor shaft and rotor
were turning with the crankshaft.



I then checked the supply and ground on both the Crankshaft
and Camshaft sensor plugs and both were getting 12v.



Also there was 12v to the coil and the module that is
mounted on the side of the coil.



Then decided to try a coil from a known running truck and
still no spark.



Tested all fuses under the hood and in the cab and all
tested good.



Checked fuel pressure, that was fine.



Now after putting the new cranksensor in I’m getting a
P0339.



Wondering if maybe ECM is bad or something, like it’s not
telling the coil to engage!?!? However I would sure think that the truck would
still run but in “limp” mode or etc.



I then started to think maybe a bad ground?!? Maybe in the chassis or something?



From the battery I’m getting 12.125ish volts when turning over,
and each plug was getting 12.5v with the key on, and the headlights were strong
as well.



I even used a jumper wire on the solenoid on the starter to
rule out the ignition ON position.



I then ohm tested the coil wire from the coil to the
distributor cap and that was well within spec.



I’ve had no recent electrical problems with the truck.



 



Does anyone have any advice as I’m at whits end here L



 



  • 4 weeks later...
aapluna Enthusiast

aapluna

Posted
Posted

ive seen this before on a customers truck and it wound up being his ecm, his was due to welding on the truck without disconnecting battery cables. not saying that you have done the same but he came in talking the same way you are as far as his latest diagnostics and parts replaced. i suggested the ecm to him because i noticed a bunch of aftermarket stuff welded on and asked if he disconnected cables and he said no.Just saying

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