[JohnWR]

I just wanted to check in and provide a quick update. If you've read all my posts here, you know I changed the ignition switch about 2 weeks ago and immediately had a "no crank" which required me to disconnect/reconnect the battery. Therefore, I assumed the issue was not resolved. However, ever since that time, the issue has not happened again. It has been cranking and starting every time i ask it to. I've driven it on multiple small drives and have started it at least once a day since that time and let it run for a few minutes. I'm cautiously optimistic that the ignition switch was the cause of my problems, but if I have an issue again, I will update this thread. I want to thank everyone who took the time to read my post and offer me suggestions, it was and is truly appreciated.

I hope that you found the problem.

 

[jimreally]

I hope that you found the problem.

So after several weeks without any issues and intermittent driving, it happened again. I was going to run an errand at lunch, started the car, and had the RPM drop, engine light flashing issue. I took a different car on the errand and decided that i wasn't going to reset it by the battery disconnect method and I would just work on it until I resolve it without a battery disconnect. I got back from the errand about 15 minutes later and I hooked my laptop/USB OBD II monitor, and started it - hoping to get some more data. Of course, it's now running normally again. I will reiterate that this is the most frustrating car issue i've ever worked on in my entire life.

 

[jimreally]

Over the weekend I did the following:

1. Cleaned the ground under the battery - it appeared to be fine upon visual inspection.
2. disconnected and inspected and cleaned the C100 connector (with electrical contact cleaner) and contacts - Though both sides looked fine upon visual inspection.
3. removed the fuse box under the hood and cleaned all the connectors and contacts - again they looked fine upon visual inspection.
4. Cleaned the positive post and connector attached to the fuse box under the hood. This did have a bit of corrosion on it, along with removing a small gold piece of metal (which had a non-conductive coating on it) that was between the nut and the wire connector. This was my most promising find as it was fairly corroded, though non-load testing readings indicated the connection was fine. Of course with the issue being so intermittent, I wouldn't expect to find an issue when everything is running fine. However, I'm not sure if that provides any power to the fuse box, or if it's only purpose is for the charging post.
   • though I removed the fuse box, I didn't actually open it up - is there any need to do that?
5. Cleaned the ground on the front passenger side by the headlights.

After all of this, of course the car is running fine - but that's what it does after any battery disconnect anyway

 

[sahein]

Did you try reseating the connectors under the passenger floor?

 

[jimreally]

Did you try reseating the connectors under the passenger floor?

Yea, I cleaned them a few weeks ago, disconnected all of them, sprayed with contact cleaner, and then connected/disconnected all of them 3-4 times.

 

[rjgramps]

Also consider doing the same with the ECM. It is located adjacent to the windshield washer reservoir. Removing the left front fender helps a lot with access which also provides an opportunity to clean out all the grime and debris that loves to collect in the area. Removing the washer reservoir helps a lot with that cleaning process.

 

[jimreally]

Also consider doing the same with the ECM. It is located adjacent to the windshield washer reservoir. Removing the left front fender helps a lot with access which also provides an opportunity to clean out all the grime and debris that loves to collect in the area. Removing the washer reservoir helps a lot with that cleaning process.

The ECM was recently replaced, however I'm not opposed to cleaning the contacts there as well. I was actually going to do that, but realizing that I had to remove the fender and that the rain was coming (I don't have a garage) i decided to put that off. I'll work on that this week or over the coming weekend.

Please keep the suggestions coming any and all input is appreciated!

 

[jimreally]

I'm going to say that your generator is okay. With the fuel gauge dropping like that it sounds like a loose wire, fuse, or relay.

So today i drove the Sky about 60 miles - 2 separate 30 mile round trips. It ran fine for the first 45 of those miles, but it started acting up on the way home on the 2nd trip. Because i had about 10 miles to go, I decided to run it like it was for a while and see if i noticed any other symptoms/gauges doing anything odd. During that test cycle, the CEL was flashing and the engine was cutting out intermittently. It would run normally for a stretch and then start acting up again. What I noticed was the only thing other than the RPMs dropping/engine cutting out, was the fuel gauge was actually goin up when the engine was cutting out, all the way to full at one point. During the last 3 or 4 miles of the trip the engine started running normally again, and the fuel gauge settled back to what i think was the normal position. The other information seemed to be fine, the speedometer wasn't jumping, the engine temp looked to stay steady, no other flashing lights or odd behavior.

Does this give anyone any ideas?

 

[agent008]

You might have faulty wiring going to your fuel pump and gauge. Almost seems like a mouse chewed the wires a bit and your fuel pump 12v+ might be touching your fuel gauge return wire?

I suggest you remove your trunk liner and have a look at the fuel tank connectors...

 

[JohnWR]

So today i drove the Sky about 60 miles - 2 separate 30 mile round trips. It ran fine for the first 45 of those miles, but it started acting up on the way home on the 2nd trip. Because i had about 10 miles to go, I decided to run it like it was for a while and see if i noticed any other symptoms/gauges doing anything odd. During that test cycle, the CEL was flashing and the engine was cutting out intermittently. It would run normally for a stretch and then start acting up again. What I noticed was the only thing other than the RPMs dropping/engine cutting out, was the fuel gauge was actually goin up when the engine was cutting out, all the way to full at one point. During the last 3 or 4 miles of the trip the engine started running normally again, and the fuel gauge settled back to what i think was the normal position. The other information seemed to be fine, the speedometer wasn't jumping, the engine temp looked to stay steady, no other flashing lights or odd behavior.

Does this give anyone any ideas?

I think that @agent008 could be on the right track, but the problem could actually be anywhere from the fuel tank to the ECM.

That said, with the CEL flashing there should be a code stored, even if the light is no longer on. Assuming that you still are not seeing pending, live, or historic codes, the only thing I can think of is a problem with the ECM.

 

[jimreally]

I think that @agent008 could be on the right track, but the problem could actually be anywhere from the fuel tank to the ECM.

That said, with the CEL flashing there should be a code stored, even if the light is no longer on. Assuming that you still are not seeing pending, live, or historic codes, the only thing I can think of is a problem with the ECM.

No codes, but I did another test, disconnected the MAF and I got 2 codes, disconnected the camshaft position sensor and got another code. I'm not saying it isn't the ECM, but it does seem to be capable of storing codes. I started the process of removing the trunk liner - this doesn't seem like a very straight forward job. Any tips? Also I have an endoscope and used that to inspect the wiring and connectors on the sending unit, it LOOKS ok, but of course I cannot be sure without getting my hands on it.

 

[JohnWR]

No codes, but I did another test, disconnected the MAF and I got 2 codes, disconnected the camshaft position sensor and got another code. I'm not saying it isn't the ECM, but it does seem to be capable of storing codes. I started the process of removing the trunk liner - this doesn't seem like a very straight forward job. Any tips? Also I have an endoscope and used that to inspect the wiring and connectors on the sending unit, it LOOKS ok, but of course I cannot be sure without getting my hands on it.

It is the fact that you have been able to force codes, but don't get one when the car is running its worst, that makes me suspect the ECM.

The liner mostly lifts out, although you have to fold it in some to do that. It has been at least a decade since I had mine out, but once the top drain tubes are out of the way and the light is snapped out of its hole it was mostly a matter of contortion. I do not remember anyhting "hidden". Obviously you want to be careful that it doesn't spring open at the wrong time and damage paint.

 

[jimreally]

It is the fact that you have been able to force codes, but don't get one when the car is running its worst, that makes me suspect the ECM.

The liner mostly lifts out, although you have to fold it in some to do that. It has been at least a decade since I had mine out, but once the top drain tubes are out of the way and the light is snapped out of its hole it was mostly a matter of contortion. I do not remember anyhting "hidden". Obviously you want to be careful that it doesn't spring open at the wrong time and damage paint.

Thanks, I got the liner up and took the cover off to look at the sending unit. There was a mouse nest in there, but unfortunately the wiring actually looks fine. There doesn't seem to be any wires frayed or chewed. I can't seem to replicate the issue or make it better by any wiggling of any wires at the sending unit nor any wires i've tried at this point. I took all 3 connectors off, sprayed them with contact cleaner and worked them in and out a few times. I also removed the fender and cleaned up the ECM connectors, but the issue came back again. The loud clicking that happens at times is coming from the throttle body I believe, and I confirmed when this happens, the power train relay, and the fuel pump relay under the hood are both cycling/chattering coinciding with the loss of power. I actually did have a condition at one point with all of my messing around where I was unable to connect to the ECM. I guess I'm going to have to try and replace that now - I'll let you know if the company honors the warranty. Also, once i get the new ECM, can I take the module to the dealership to program, or does it need to be in the car for that? (I really don't want to tow it there), Here's a picture of the mouse nest:

 

[agent008]

The loud clicking that happens at times is coming from the throttle body I believe, and I confirmed when this happens, the power train relay, and the fuel pump relay under the hood are both cycling/chattering coinciding with the loss of power.

This certainly points to the ECM or its wiring. Not sure if you wrote about this and I didn't notice, but surely this symptom points away from the pump and sender connectors.

Replacing the ECM would be easier than troubleshooting wiring so let's hope the ECM is indeed the issue and that you can get it replaced without cost.

EDIT: I do believe that removing the trunk liner and checking your tank wasn't a waste of time anyway. Good opportunity to get rid of the mouse nest and all the dirt and debris. And now you're aware it'd be good to recheck the area every now and then lest another critter decides to make the place its home

 

[jimreally]

So i went back out to my car tonight to move it up in my driveway. When I started it, the engine light was on, not blinking this time and the car was not cutting out as it had been, instead it was running really poorly. It felt like it had a broken motor mount the way it was shaking. I hooked my monitor back up to it and i had 2 codes this time that I did not purposefully cause: P0606 and P1682. From my scan tool:
P0606 - GM

Type	Powertrain - Computer and Auxiliary Outputs - ISO/SAE Controlled
Description	Control Module Internal Performance Conditions
Cause	DTC P0601 and P0604 not set, key on, then the PCM determined that an internal performance problem existed within the controller • Refer to code repair chart for instructions on how to replace a PCM and how to reprogram a replacement

and P1682 - pointing to ignition issues.

So this kind of confirms that the ECM needs to be replaced and that the primary issue that is being caused is a loss of ignition.

Also interesting to me, i shut the car off, got the scanner and scanned it. Then i started it again to move it forward, and it was back to running normally. It's like this car is possessed.

 

[agent008]

It's like this car is possessed.

This kind of random behaviour suggests wiring. The ECM is throwing a code about its outputs being faulty. Might be that the outputs are fine but the wiring from outputs to whatever is being controlled (coils/plugs, camshaft solenoids, evap system, etc.etc.) is faulty. The ECM has no real way of knowing if it's its own outputs that are bad, or the wires that plug into those outputs. The presence of a mouse nest atop your tank reinforces the wiring hypothesis.

A recent case of rough engine over on Solstice Forum involved months of head banging and investigation, and a bad (brand new) coil turned out to be part of the cause. The other cause was debris into the intake manifold severely restricting air flow to one of the intake ports of a cylinder.

A bad coil, plug or coil wiring might be your issue. Wouldn't hurt to check the coils and plugs?

 

[jimreally]

This kind of random behaviour suggests wiring. The ECM is throwing a code about its outputs being faulty. Might be that the outputs are fine but the wiring from outputs to whatever is being controlled (coils/plugs, camshaft solenoids, evap system, etc.etc.) is faulty. The ECM has no real way of knowing if it's its own outputs that are bad, or the wires that plug into those outputs. The presence of a mouse nest atop your tank reinforces the wiring hypothesis.

A recent case of rough engine over on Solstice Forum involved months of head banging and investigation, and a bad (brand new) coil turned out to be part of the cause. The other cause was debris into the intake manifold severely restricting air flow to one of the intake ports of a cylinder.

A bad coil, plug or coil wiring might be your issue. Wouldn't hurt to check the coils and plugs?

When I saw the mouse nest, I was actually happy - figuring I found the issue. However, even though there was a lot of debris on top of the tank, the wires looked to be untouched - no chewing anywhere between where the wire is not running through the interior of the car and the sending unit and my very (un)scientific test of wiggling the wires around in that area didn't seem to affect the car at all - How can I actually test that wiring and the sending unit?

Also, any advice on how to "test" the coils? I can pull the plugs easily enough and check them, though that would really be a head scratcher to have a bad plug and/or coil causing me a complete loss of power to the ignition system? Honestly, even a short on the fuel pump sending unit causing a loss of power on the ignition side would seem odd to me.

Does anyone have a pinout diagram for the PCM connectors for a 2007 sky base?

 

[sahein]

A bad coil would set a miss-fire code.

 

[jimreally]

And for anyone interested, here's the sound from under the hood of the car with the ignition in the "run" position. This doesn't happen ALL the time, but when it is giving me the "no crank" condition, when I turn the key to "on" and leave it there for a while, it'll start this clicking and the relays actuating, with the corresponding in tank fuel pump kicking on/off. I think this noise is coming from the throttle body?

Loud Clicking noise

 

[agent008]

That has got to be either the ECM outputs or the wiring. I'm not sure whether you should install a replacement ECM right away. Might be the wiring damaging the ECM. How to test the wiring? Let's wait for other members who are more knowledgeable than me to chime in, but I think a course of action would be to get a multimeter with continuity beep function and test your throttle body pins. One probe at the ECM connector end, the other at the throttle body end. Then do the same with the fuel pump relay. One probe at the FP relay coil input, the other probe at the ECM connector. If you find no fault then it should be the ECM.