UPDATE!!! 08 Suburban 5.3 ckp issue!!!!!!

Hi, I have a 2008 Chevy Suburban 1500 LT 5.3L Flex that has got me puzzled. I am not sure exactly what my issue is and could use a little help. The truck lost tach and is showing service stabilitrak, service traction control, and is running rough plus hard shifting. I did a scan with the snap-on solus ultra and got code P0335 ckp circuit A. I changed out the ckp and went to do a relearn but am showing no engine rpms on the solus? It is showing ckp rpm's and cmp rpm's but no active counts on the ckp only on the cmp. I know this is the isssue with my truck but cant for the life of me figure out what is happening. I need to know what wires going into the ecm are the wires coming from the ckp so I can attempt a jumper to see if I have a broken signal wire or what in the world is happening! Thanks for any help you can give me on this issue.

I got the pin schmatic and tested voltage on the wires at the ecm and this is what I got... Reference wire has 5.03v constant, Signal wire has 2.38v constant. I have no idea why that is? I have the voltage with it plugged in and unplugged same thing! I thought maybe it was the two wires making some sort of connection together in the harness so i ran a new wire from the ecm signal to the CKP but same thing happened. I hae a theory that the CMP could be shorted or bad and that could be causing the issue but the truck runs? Any thoughts Thanks guys!

How does the low reference look for the crank sensor? Aka the ground. Also if this is a pull down type sensor you might have a bad pcm not supplying 5 volts to the sensor on the signal wire. Try checking the same signal wire for the cam sensor betting it’s going to be 5 volts unplugged

I tested the wires to both the ckp and the cmp and got 5.03v on both reference wires and on the ckp I get 2.38v on the signal wire and I get 5.03 on the cmp signal wire. I get 0v on the low reference wire on both. I have checked the entire harness pulled it off and inspected it and found nothing there. I changed out the ecm and the bcm and still get the same exact thing? I can't figure it out and it is driving me nuts. I usually have no trouble figuring things like this out but this one has me stumped for sure! Thanks for the info and I hope someone can give me something that I haven't tried yet!

Make sure there’s no corrosion or anything on the pcm connector that’s pulling the voltage down. Check powers and grounds at the pcm maybe one has resistance in it. Backprobe use headlight bulb load them.

Also check terminal figment for that signal wire

Pulled fuse block and checked all pins and terminals all were good reinstalled and still get the same issue. I still have no rpms showing on the scan tool and still getting the wrong voltage on the signal wire fro ckp and no pulse from it. I will be cleaning all grounds and possibly adding a new one just because.

Might seem redundant at this point, but to be clear;

The 2.38 volt constant on the signal wire, does disappear when the PCM and sensor is unplugged?

Was the truck running when you measured this voltage?

Edit;

With the sensor unplugged and a test lamp to ground, does repeatedly touching the signal show rpm on the scan tool or cluster?

Will your scan tool perform a crank relearn?

The 2.38 volts seems like a DMM average reading plugged in vehicle running.

I am unable to do a relearn due to lack of rpms. havent tried grounding the signal wire to see if the rpms change on the scan tool. I cleaned all the grounds and did find one loose but it did not fix my issue. I also looked at the harness above the front drive shaft and it had been repaired so I looked it over really good and it all seems good and tight.

Also you might want to try cutting that signal wire where it can easily be repaired close to the pcm and check the voltage again on that wire. Problem could be in the connector at the sensor. Have you checked it for a short to ground sensor and pcm unplugged ohm meter on battery negative and probing signal wire should be infinite resistance

I apologize for my error I get 4.7v KOEO ckp unplugged and 2.3v KOEO ckp plugged in I also get the same signal with it running on the ckp.I get the same with the cmp but the cmp signal fluctuates from 2.2v-2.7v in that neighborhood. I inspected the sensors and the reluctor wheel and both are fine. I have not done a short to ground on the signal wire but will do that shortly. If it is short to ground what would be my next step? Thank you guys for all your help so far!

Went ahead and did a short to ground even though I didn't think it was. I was correct it was not shorted. I am using a Brand New OEM ckp and it is the second one I bought just to make sure I didn't get a defective one. I also noticed today one heck of a spark connecting the battery terminal back to the post with the doors shut and everything off. Possible short somewhere else? I was pretty powerful of a spark and that i know is not usual in most cases. I have access to a known good engine harness that I will be getting Monday to rule out wiring being the issue. Also I would like to thank all of you for your time and insight into my issue.

Stupid question how’s the mounting surface for the sensor? Nice and clean no rust? You replaced the one behind the starter correct?