Jarvisw

New to forums, but not shadetree repairs

I have an 04 Venture with a 3.4. I have a p0300 code, and have REPLACED near EVERYTHING with new mostly AC Delco parts. (Plugs, wires, ICM, EGR, another PCM retied to VIN, swapped coils, BOTH Crank sensors, cam sensor, etc)

None of these changed the misfire.

It does not fire the Pass side coil. The 5/2. I can put a timing light on the other ones and they fire, but not those two. As I said, I moved the coils and replaced the ICM and neither changed results.

NOW, what I think is going on, and have checked it when its acting up, is its not getting 12v from the PCM to the CKP x24.

My question is, should this be powered all the time, or does the PCM sense a problem, and shut down the voltage to the CKP? It doesn't make sense it would do that, but its the only think I can think of.

I want to jump a wire to it, but if the PCM is doing it, then I have another issue, and not an open circut.

Hoping someone has seen this before, thanks!

Also, find it funny that FORD is the sponsor for the Chevy Forums.. Its either clueless, or the best marketing move ever lol

burhead1

All the firing is done with the ICM, so if your coil is good then you have a bad ICM or the wrong ICM.
Also check to see if you are missing teeth on the reluctor rings.

Jarvisw

I forgot to add that I replaced the Harmonic Balancer OEM too.

Like I said, there is NO power to the CKP when its acting up, and when there is (rarely) the engine works right. ICM was also AC-D, and does the same thing as the original one does.

So, really, is there supposed to be power to the CKP the whole time, or will the PCM shut that off?

I WOULD just jump it off, but I'm afraid that might fry the PCM if its not expecting a signal from the CKP?

burhead1

Check the pink wire on connector C2 going into the ICM as it is the supply voltage to the ICM, it may not be providing 12v when your ckp is dropping out. the 3 wire ckp light green wire should be 12v if not that voltage is supplied through the ICM


The red and white wire to the cam sensor is a 12v from the PCM, if you are loosing power on that wire then you have a bad wire from PCM or you have something else (sensor, actuator) causing the 12v reference to drop. Also check all powers and ground going to the PCM.

Jarvisw

The Pink wire had a pure 12v last time I checked, but that was a while ago, tho it was messing up then too...

The CKP x24 is the one with no power, and it seems to go straight to the PCM. Blk/Y wire should have 12v there but does not at the sensor. (I will double check all this, wire color too, its just been too cold, and was hoping someone else knew this issue offhand.)

The rear CKP x7 seems to be sending the correct signal, or at least has the right OHM range for it. I saw to really check it to use an oscilloscope, but I havent seen one of those since high school electronics! lol

I didnt want to, but I think my first step will be to find the CKP x24 power off the PCM and check its power there. Just didn't want to dig into that rats nest of wires.

Thanks for the advice! I will do those steps too as I continue to chase this down.

chevy47390

DTC 0300: multiple random misfire cylinder detected.

I agree with burhead 1:" All the firing is done with the ICM, so if your coil is good Then You-have a bad or the wrong ICM ICM."

for information:
one day I launched the starter, PCM unplugged, ignition seemed OK.

ignition would be independent of PCM, ICM receiving information from CKP7x.
the CKP24x is powered by the PCM and sends processed information for controlling the injection
"My issue is, shoulds This Be powered all the time, or Does the PCM sense a problem, and shut down the voltage to the CKP? It Does not make sense It Would Do That, drank its the only think I can think of."
As all sensors, KPC is supplied and must be constantly to give the KPC information. This is to check on a venture without problem.
this poses a problem already mentioned: Does anyone has it the wiring (with output numbers) PCM? for different venture before 1999 and after 1999

real or wrong DTC ?
You have a 0300 code, but are these misfire noticeable to driving? in case of misfire, the O2B1S1 lambda should also cause a DTC.

Jarvisw

Hmm. Well, I may have two problems, but why would BOTH ICMs do the SAME thing? Oh, and I checked the wire from the CKP x7 and its got proper OHMs.

Also, its the YELLOW/Black wire that has intermittent power. I'm about to check it at the PCM (and BOTH PCMs were not giving constant power) Im betting that problem is an open Y/B wire in the harness.

Yes, its VERY noticable, seeing as how its only running on 2/3rds power, as 2 plugs aren't firing at all. Tested by timing light.

Jarvisw

Ok, I checked the Yellow/Black wire for continuity off the PCM to the sensor. It had it.

I checked for power off the PCM, it DID NOT have it.

So, why would the PCM not send power to the 24x? BOTH the original and the one that I got to try to fix this problem, (and set to my VIN) does the same, no power thing!?

(Yes the key was on lol)

burhead1

Need to test all powers and grounds going into pcm, it won't come out if it's not going in.
Test all your connections using the volt drop method see pic. volt drop is setting your volt meter to dc and using the positive and negative across the circuit, your meter should rear 0.1 to 0 if the circuit is good if not it will read higher.

Jarvisw

Well, the only connector in question right now(?) is the one in the PCM to the wire, kinda hard to test that for drop. I have it unplugged from the sensor to test continuity, and it used to occasionally send voltage down that way too, just test to chassis ground... Both the Ohms and volt test was from 1 inch out of PCM, I used a small pin to pierce the wire.

Anyway, what other ground to the PCM is there besides the harness? It floats in the plastic box. I hooked up the upper engine brace just in case, but thats got rubber insulating it.. Where else would grounds be? I guess I haven't seen a classic "ground strap"

Thanks for help, I hate electrical issues.