2001 Chevy Tahoe 5.3 No Spark In 3 Cyl.

HI everyone!

I'm working on a '01 Tahoe with the 5.3 The computer is not sending the signal to the coils #5, 7 and 8. I'm not familiar with this 24X crankshaft 1X camshaft relationship.. i'm looking for some information and maybe a known good CRANK/CAM sync waveform..
I have to crank the engine for 10 seconds to make it run but it only runs at 380/500 RPM sometimes i get P0336 CKP "A" (18/24X) OUT OF RANGE. But i think i'm getting this code because i'm cranking the engine to much to get it running!

do you have power and a ground to these coils? or just no control?

I just don't have the control signal from the computer

id check it at the engine control module next. to eliminate broken control wires

I did check the control wires for all the coils they are OK.. I just received a ecu that i ordered and still the same. I'm researching right now how the computer receive the signal to fire the coils.. But no luck so far

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I'd absolutely follow the P0336. The 24X signal on this engine is kinda bananas, as it's actually two separate reluctors sandwiched together on the crankshaft. The CMP is just a high/low transition every crank revolution.



It's kinda tough to tell in that capture, but there's intermixed short and long pulses at work. If you can capture the CKP while the engine is idling, then I'd suggest making sure that there are indeed 24 pulses in one CMP pulse. Anything less will confuse the PCM.

I will try to capture CKP and CMP tomorrow! And post screenshot of the waveform

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Sweet, thanks sir! This is an interesting symptom, so I'm very curious to see what you find.

Here is the waveform!

Thanks, sir! Could you email me that VSM file? wrenchturnsyou@gmail.com

I'm interested to take a closer look, as it appears that the last pulse of the CKP gets cut off by the end of the CMP pulse. Might just be the way the image came out?

Thanks for the waveform! Had a look, counted the CKP pulses. Definitely had all 24 pulses within the CMP window. I got a little concerned at how close the last pulse is to the end of the CMP, but I'm not convinced this is the issue:



This was during cranking, correct? Do the same three coil not have spark during cranking, as well as idling?

Tyler wrote: Thanks for the waveform! Had a look, counted the CKP pulses. Definitely had all 24 pulses within the CMP window. I got a little concerned at how close the last pulse is to the end of the CMP, but I'm not convinced this is the issue:

This was during cranking, correct? Do the same three coil not have spark during cranking, as well as idling?

That was at cranking!
One thing i noticed when i was triple checking the inputs at the coils is that in the first cranking i get one and sometimes 2 spark at the coil # 5..
Im going to check it again and i post any update

Here is a screenshot of the CKP,CMP and coil #5 on initial cranking .. it's getting just one or some times 2 signals every time i first crank the engine.

i checked the other "2 faulty" (coils 7 and 8 ) coils and i'm not getting any signal at all on initial cranking.

It probably doesn't indicate anything, but I'm noticing that a lot of the noise on the turn on pattern just kind of goes away after that initial turn on.

Did you happen to capture a known good from a working coil?

HI NOAH!

Here is a capture of a CKP( BLUE) COIL#1 (YEL) COIL #2 (GREEN). I connected the ground at the battery. And to be honest i can't remember where i connected the ground when i test the COIL#5..
i think the noise it's because the starter is cranking the engine! don't you think ? i did notice the noise but i just tired of this truck that i didn't care much.. but tomorrow i will check it again to make sure where i connect the ground..

Are you checking the signal wires with the coils unplugged? or have you swapped or replaced any of the coils?

Maybe something weird on those coils shutting down the drivers

So I've been beating my head against the wall on this one. :lol: To be completely honest, I probably would have broken down and tried a crank sensor already.

Started thinking about the cylinders that are missing spark. The firing order is 1-8-7-2-6-5-4-3 on this engine, which slices up like this:

1-8-7-2
6-5-4-3

So #8 and #5 are companions, two of the cylinders we're missing spark on! #7 is just after #8, so maybe there's something to that? Anyway, I started wondering if there's something wrong with the crankshaft reluctor, as #5 and #8 are 360 crankshaft degrees away from each other.

Threw the overlay program up over the coil trigger waveform jaivs26 posted, hoping to associate crank pulse groups with specific cylinders.



If I did it right, then it's the second group that's associated with #5 and #8. The short-long-long-long group, right after the initial short-long-long-long-long-long. But, I can't find anything wrong with it! :lol: :silly:

I want to thank everyone for helping me with this problem. All have been very helpful!!
today i was checking it again a notice that the alternator was getting hot just a few minutes when the engine was running.
and something weird to me happened the engine start to get more speed. Unfortunately it didn't fix anything.

I tested the alternator with the KOEO and heres the capture

I also recored a small clip when i found this

i did swapped the coils and i'm checking the signal with the connectors plugged in!

I can't watch that video right now. But it seems like unplugging the alternator improves the symptoms? I'd be interested to know how much AC ripple is present at the battery.

Thinking back now, that'd probably explain all the noise in the CKP signal peaks...