SOLVED! 05 Envoy Denali 5.3L no crank, no start, codes P0335 and P0340

[clevdan]

Hello all. I’m new to the forum and am having an issue with my daughter’s 05 Envoy Denali with the 5.3L V-8 that has me ready to pull my hair out. My son-in-law and I removed the transmission at a friend’s shop Saturday to replace the rear seal on the engine. The exhaust pipe with the cats gave us the runaround trying to get them out but we finally got them. Replaced the rear seal and the transmission. When we attempted to start the engine Friday night after the job we got a no crank, no start issue when turning the key. Along with the no start, no crank was a P0335 Crankshaft Position (CKP) sensor circuit (Symptom 00) and a P0340 Camshaft Position (CMP) sensor circuit (Symptom 00) codes. No issues with no start, no crank before this rear seal job. This is not a DOD engine. I am not getting a security light.

We went back to the shop Sunday to begin troubleshooting. I did some research Saturday night after getting home and came across a couple of posts where guys have pretty much the same symptoms I have and they corrected it with a new ignition switch. Since that’s a fairly cheap, easy repair and seems to be quite the issue with these vehicles I installed a new ignition switch first. The engine started the first try and then went back to no start, no crank on the second try with only the CKP code this time.

Looking at the wires going to the CKP the section of the harness close to the starter the wires were hard and the insulation was pretty brittle. Looking further back in the harness we found all three wires with skinned insulation about 10 inches from the CKP connector. I figured we might have damaged these wires while we were wrestling the exhaust pipe out. I installed a new connector pigtail cutting and connecting one wire at a time being extremely careful to get the wires correctly pinned. Plugged the harness in, installed the starter, the engine cranked and started once then no crank, no start with CKP code.

My son-in-law has a zipper on the starter now. He must have had the starter out and back in at least twenty times. If the starter is out laying on the frame rail, turning the key will spin the starter EVERY time without logging any codes. Put the starter back in and about half the time the engine will start once without codes and then go back to no start, no crank with either both CKP and CMP codes or only the CKP code.

It started getting late Sunday, it was my buddies anniversary and we needed to get out of his shop and let him get home to his wife so as much as I dislike the practice I pulled out the parts cannon. I have replaced the;
Ignition switch having removed and reinstalled several times to be sure it was in correctly
CKP sensor and pigtail connector
CMP sensor (once we found it at the front of the engine) along with the CMP intermediate harness

Today I had the truck towed to the house. I was planning to run new harness wires from the PCM to the CKP but I found a tutorial online to check the CKP circuit and it checks out good. I have 12V at the CKP (having back probed the connector) and voltage on the signal wire changes from 10.5V to .5V as you turn the crankshaft with a ratchet and socket.

Sunday we swapped the Starter and Powertrain relays with no change in symptoms. Today I verified continuity from terminal 87 (the terminal in the fuse box) of the starter relay to the start terminal on the starter. I also verified 12V at terminal 30 at the relay. However, when I jumper 30 to 87 I get no crank, no start. I jumpered Battery + to terminal 87 and again, no crank, no start. Again, these were the terminals in the fuse box.

I have verified inputs to and outputs from the ignition switch.
Red and red/white are hot at all times.
White is hot in Accessory, Run and Start.
Orange is hot in Run.
Yellow is hot in Start.
Brown is hut in Accessory and Run.
Pink is hot in Run and Start.

One other tidbit. The truck does have an Omegalink remote starter from Caralarm that I installed 3 years ago and has been working flawlessly since the install. When I try to start the truck with the remote start I can feel it energize the starter relay but again, no crank, no start and the CKP code.

This one has me stumped. Why does the starter spin every time when laying on the frame rail but very sporadically when bolted to the engine? Why does the CKP sensor (and sometimes the CMP sensor) throw codes when the starter won’t even click, much less move the crankshaft, but never code when the starter is spinning on the frame rail? I was thinking maybe an EMI issue with the sensors since the CKP harness runs right beside the starter but I have laid the harness and sensor ON THE STARTER laying in the frame rail and it doesn’t code when the starter spins, only when the starter is bolted to the engine and DOESN’T spin! Why doesn’t the starter spin when I jump the Starter relay terminals with 12V from the fuse box or the battery?

I apologize for the mini novel here but wanted to give as much information as I could to answer as many questions as I could from the get go. I’m hoping someone can offer me some insight.

 

[Mooseman]

We do have a article in the FAQ that talks about no crank situations. Although it's for the 4.2L, the principles are the same:
No Crank, Like Attempting To Start In Drive

However, cutting to the chase, if you are jumping the relay, the starter should crank, period. Also, does it crank if you jump from the battery lug to the solenoid on the starter (basically shorting with a screwdriver)? If it does, then the battery power to the starter is good. Does the relay click when you turn the key? If not, check for power at the other leg of the relay and that the PCM is sending ground to the other leg. Another possibility is a broken trace under the fuse box.

For the codes, they say specifically a problem with the circuits for the sensors. Grab the schematics for these circuits (check the link in my signature for manuals) and see if there is a common circuit that could affect both. Maybe a ground wire broke or they're shorted to each other. Trace the wires to the PCM and check for shorts between them.

Edit: It's possible that it's throwing these codes because the engine is expecting to see signals from them when it thinks it's cranking but because it's not, it's assuming there's a problem with them. Fix the no crank issue first.

 

[clevdan]

Hello again. Sorry for no update yesterday but by the end of the day I was tired, sweaty and just wanted to drink a beer or five! 🍺🍺🍺🍺🍺 It always kind of bugs me when these threads are left hanging with no resolution, so here it is. For those of you that read the last page of a book to find out the ending before you start, I had to replace the starter. That corrected the problem.

What follows are my thoughts on why I was getting the codes I was getting and why I didn’t just go straight to replacing the starter.

Item first; I was on a time table which is never good (at least for me) for intelligent, systematic troubleshooting. As I mentioned in the first post I would rather troubleshoot and only replace the bad part but in this case I had to get the truck out of the shop. So this is a perfect example of what can happen when you fire the parts cannon. In this case the ordinance department (my frazzled brain), loaded the wrong ordinance. This was supposed to be a simple drive it to the shop, replace the rear seal and then drive it home kind of job. This is my daughter’s truck and she has had absolutely zero starter issues until this day. We were done with the rear seal at 3:00pm and then the starter began acting up.

Item second; the fact that the starter would spin in the frame rail and then start the engine once after reinstallation threw me. If you take a starter to the auto parts store for testing their machine does pretty much exactly what we were doing with the starter laying loose in the frame. I didn’t want to spend $240.00 on a starter just to find it didn’t fix it.

Tuesday after getting the truck to the house I verified starter relay terminal 87 in the fuse box showed continuity to the start post on the starter. When jumping terminal 30 to terminal 87 and battery + to terminal 87 did not make the starter crank, at this point I should have made the call that the starter was bad. Except it did crank and start without coding three times after that and then went back to its old tricks.

After having some very strange symptoms in the past from loose/corroded grounds I disconnected and cleaned all the grounds leading from the battery to the block and the chassis. No change in symptoms. I finally loosened the right side motor mount, jacked the engine up and shorted the terminals on the starter itself. All I got was tiny sparks. At this point I finally gave in and bought a starter.

I’m still not sure why the starter would spin in the frame rail but only intermittently when bolted to the engine but I think I can explain why sometimes I got no crank and no code, sometimes I got no crank and P0335 Crankshaft Position (CKP) sensor circuit and other times I got no crank and P0335 Crankshaft Position (CKP) sensor circuit and P0340 Camshaft Position (CMP) sensor circuit. I’m more of a Detroit Diesel/Allison Automatic Transmission mechanic than an automotive mechanic. I only work on my automobiles and then only when they make me. That and I’m too cheap to pay someone to do something I can do myself.

The following explanation is a SWAG (Scientific Wild Ass Guess) based on my knowledge of the Detroit Diesel Electronic Control system, DDEC in its various versions from I to V. If I’m not exactly right, I’m sure the automotive master techs will correct me but please don’t flame me. I’m not writing this for the master techs but to shed some light for the DIYers who might be confused by the different symptoms like I experienced.

I’ve never seen a code for a failed starter. So the ECM/PCM (Electronic Control Module/Powertrain Control Module) can use the CKP and CMP sensor codes to point in that direction. When the ECM gives the start command by grounding the start relay coil, it is expecting to see RPM through both the CKP and the CMP. DISCLAIMER; the following numbers are used for explanation purposes only! The ECM will wait a certain amount of time to see the CKP pulses before logging the CKP circuit code, say .5 seconds, for the sake of explanation. Since there are many more crankshaft sensor teeth than cam sensor teeth, and you only get one cam pulse every two revolutions of the crankshaft, let’s say the ECM will wait 1 second before logging the CMP code. Again, I’m picking numbers out of the sky for the sake of explanation.

So for no crank no start, using the numbers above, how long you hold the key in the start position will determine the result you get. If you hold the key in start for .25 seconds you will get no crank, no start, no codes. You didn’t meet the CKP code threshold. If you hold the key in start for .75 seconds you will get no crank, no start along with a P0335 CKP circuit code. You met the CKP code threshold but not the CMP code threshold. If you hold the key in start for 1.25 seconds you will get no crank, no start along with a P0335 CKP circuit code and a P0340 CMP circuit code.

If I was to do this all over again and not be on a time limit, my first step for a no crank no start would be to jump starter relay fuse box terminals 30 and 87. If the starter cranks it verifies the start wire to the starter and the starter are good. Now you need to work backwards towards the ignition switch and the battery. If it doesn’t crank, after verifying continuity from terminal 87 to the start post on the starter, then it’s time to change the starter.

Good wiring diagrams are a must for this type of work. Mooseman, THANK YOU VERY MUCH for the Trailblazer and Envoy Service Manual downloads!!!!! I also purchased a 2002-2005 download Service manual from EvilBay which turned out to be some of the same ones I got from you so I could have saved that $8.00.

I found a great tutorial on checking the CKP and CMP Hall effect sensors with a volt/ohm meter (which I’ve always been told is not possible, so I learned something there) at https://troubleshootmyvehicle.com/gm/4.8L-5.3L-6.0L/how-to-test-the-crank-sensor-1 .

I use the Tool Aid - 20 Piece Back Probe Kit (23500) for back probing connectors to test the CKP sensor. It can be found here https://www.amazon.com/dp/B00G9C3RSU/?tag=gmtnation-20 .

Because they are required tools for Detroit Diesel/Allison Transmission distributors and I have them in my toolbox I use the Kent-Moore J-39197-A or J-48476 jumper wire kits. These allow good jumpered connections without the chance of spreading terminals (especially in a fuse box) and creating a problem you didn’t have while you are searching for the problem you do have. They are quite pricey but since I already have them they’re what I use. I’m sure there are others out there that don’t have the gold plated Kent-Moore price.

So that’s, as Paul Harvey would say, ‘The rest of the story.’ Again I apologize for the length of the novel. But if it was too long for you, you should have stopped reading and gone on to another post. 😂 I hope this can help someone in the future.

 

[Mooseman]

I'm going to add this one to the FAQ as the codes could throw people in the wrong direcition.

I pointed you in that direction because I have seen the same thing on my snowmobile. Yep, fuel injected and ECU controlled, when the starter solenoid failed, it threw a crank sensor code.

I'm gonna have to test this on the 4.2L to see if it does the same thing. Just pulling the starter relay should do it.