- Hello, I'm working with a 1999 K1500 5.7 350 vortec suburban 4wd ,K series.
- Was misfiring cylinder 3 and 4 after head gasket replacement. Since then I've replaced , CPK sensor, Cam sensor, distributor cap, all new spider injectors, spark plugs and wires. Also fuel filter replaced. Now after my most recent was the cpk sensor and when i fist started the truck the snap on scanner reported no codes, no misfiring , everything seemed fine. I turned the truck off, disconnected battery charger and put some tools away. Now started the truck and prepared to drive but this time the truck started rough and scanner reported misfiring cyl7, evrything was shaking. I killed the engine noticing truck was about to die. Only current DTC code is P0339 intermittent signal from Crank position sensor (CPK). When i try to start the truck now the crank sounds very hard and will not start. I disconnected new cpk sensor and installed old sensor and exoeriencing same outcome. I have the positive and negative terminals disconnected and touched them together to drain all power throughout truck . I wanna use the scanner to re learn the cpk sensor but without the truck starting i cant use the scanner to relearn the cpk? Here soon ill recconect the battery and try again. Hopefully yall have some good advice if this don't work
I'm a suspicious man so with that P0339 intermittent signal from the Crankshaft Position Sensor code I'd be suspecting the wiring or connector for that CKP sensor. But I'm also a lazy man who doesn't like crawling under vehicles unless I have to so I'd put that code aside for a minute.
I'd pull the ignition coil wire off of the distributor cap and test for spark on it (while cranking) with an HEI ignition spark tester.
If there's spark on that coil wire, I'd make the assumption that the CKP sensor, the Ignition Control Module, and the PCM circuits are all OK.
I'd pull the distributor cap off and inspect the cap and rotor. I'd grab the rotor and see if I could rotate it back and forth. I shouldn't be able to. If I was able to rotate it back and forth some, I'd buy a new distributor.
But if I wasn't getting spark on that coil wire, then I'd start thinking about that P0339 code again.
But I wouldn't crawl under the truck just yet.
Here's the ignition system circuit:
So I'd work my way back through the circuit. 1st testing the ignition coil for power and the Ignition coil control signal from the ICM.
If it's getting both I'd replace the ignition coil.
If it's only getting power but no switching signal then move back a little further in the circuit and test the ICM (Ignition Control Module) to make sure it's getting power, ground, it's outputting the Ignition coil control signal to the coil, and it's getting the ICM control signal from the PCM. If it's getting everything it needs but it's not outputting the Ignition coil control signal, I'd suspect a bad Ignition Control Module.
If the PCM isn't providing the ICM control signal there, then it's time to drag my lazy butt under the truck and test the power, ground, and signal at the CPK sensor. Here, I'd carefully inspect that sensor's wiring and connector for any issues like corrosion, loose/broken wire(s), or a short to power or ground. If it's all there then make sure that CKP sensor signal is making it to the PCM. (no open/short in the sensor signal wire between the CKP sensor and the PCM)
Here's a couple of links that will walk you through, Step by Step, on how to do all this. You'll need a cheap multimeter and a test light. I like to use an LED test light when dealing with a PCM or any control modules. (it's safer)
https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/ignition-misfire-diagnostic-tests-1
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-1
Here's your PCM pinout charts to show you on which connector and pin that CKP sensor signal enters the PCM:
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/pcm-connector-pin-outs-1998-1999-page-1
Thank you. First since im already in the process. I have the cpk sensor out again. And this time instead of just assuming the 2 shims already installed fron the old sensor i just put them on the new one. I'm gonna put the cpk sensor back in with little pad on end and no shims installed and measure exact amount of space needs shimmed to make sure the sensors in the correct adjustment/position as ive noticed. The old sensor may have had 2 shims although the tip of the sensor still has very slight, noticable but slight scratches
- Well you can't reset the crankshaft position sensor without the vehicle running it has to be running for the machine to do its but it says intermittent signal so I'm assuming there's either short and the wiring or the sensors been shorted out when work was done pray it didn't feedback and short out the driver circuit in the computer which would mean you'd need a new computer
If my computer driver circuit was shorted out wouldnt that make my scanner unable to read any diagnostics or DTC codes
Also may i add none of my fuses have blown inside fuse panel or outside.
Alright .. haha loving it. So yesterday put my waiters on soon after pulling my spark plugs wound up probably pissing out the rest of my fuel.. good news I've regained "cranking compression" . Shoulda checked that in the first place cause my brothers thinking tomorrow pull sensor As for the crankshaft position sensor, lets say if the sensor was not properly aligned and is missing the conncection with the crank would that cause me to not have spark to my spark plugs when i touch the plug and and spark plug to metal. Either that and i probable should get more gas .
- Ok. I wish i could post pictures of the scanner diagnostics snap on solus edge. Any how . Just ran and idled so 9 minutes. All cyclnders firing with no misfires according to charts. So thats good. Turned off engine. Try turning back on and shortly 4 seconds cranking and locked up. Pushed down gas pedal WOT began cranking and 2 seconds locked up.. Fuel was 1 year old at one time. 1 month ago i replaced fuel filter, filled gas with 3 gallons. And refilled today with 5 gallons and the truck was sitting 2 months before i put stabilizer in. Im not sure what else could be the problem. Im thinking maybe see inside upper manifold and see if looks like the replacement of my spider enjectors was good. If not mentioned above i replaced those this past week.