2007 suburban misfire

[Coalkracker]

Hi everyone, I'm not very forum savvy so I apologize in advance but here it goes. 2007 suburban 230k miles. I was driving one day and all was fine, I stopped at a flag man in a construction zone and check engine light came in and started running very rough. Also traction control lights came on too. Turned around and on my way home engine light started blinking and transmission started shifting much harder. It's running disgustingly rich now! This happened about a year ago and I've been driving my backup vehicle since. Now I'm trying to fix it and I'm stumped. I've tried plugs, wires, coil, TPS, seafoam a few times, checked evap purge valve, and probably more things that I've forgotten about. It's throwing codes like crazy and sometimes they change. I ran it today and got p0300 random/multiple misfires, p0328 knock sensor bank 1, p0615 starter relay, p0573 cruise control switch, p0354 ignition coil d, p0358 ignition coil h, p0443 evap valve, p0328 knock sensor 1 bank 1, and c0561 stored engine speed/pedal position out of range. The starter relay and cruise may or may not have been there before, but I remember cruise not working for a little while before this happened. Also if I'm running at night it seems that the lights have a slow pulsating to them. What the heck could be going on here? Any input would be a great help! If any more info is needed I can do my best to provide it.

[asilverblazer]

All the codes are issues related with the circuit or sensor performance (incorrect voltages). 

 

Start checking wiring for corrosion, chewed wires, etc. I'd start at the underhood electrical center. I suspect that battery voltage is hitting the circuits the sensors are on. 

 

Truck is in limp mode, that's why it is running so rich and shifting hard. It will quickly kill the catalytic converter if not fixed.

[Coalkracker]

So can I try to narrow it down by looking at those specific circuits? I'd also like to add that sometimes when I start it, it seems normal then a few seconds later I hear one click from inside the engine compartment and it starts making a faint "noise" or "sound" that I can't explain and starts running very rough. I can make the sound go away by clearing the codes but it comes back a few seconds later. I also noticed that it's reading 74 percent ethanol in my fuel even though I'm using ethanol free fuel. Idk if any of that info supports or goes against what was said about the wiring but anymore feedback would help greatly.

[richard wysong]

Could be a ground problem as well, Those trucks are notorious for ground problems

[Coalkracker]

Today I cleaned the grounds on the front passenger side of the engine block. I read the other grounds only affect charging? Idk if that's true or not but I can try the others just in case.

[asilverblazer]

14 hours ago, Coalkracker said:

Today I cleaned the grounds on the front passenger side of the engine block. I read the other grounds only affect charging? Idk if that's true or not but I can try the others just in case.

No, it's not true. There are a bunch of grounds that close numerous circuits.

 

P0328 includes abnormally high voltage from the knock sensor.

P0573 references a high voltage signal in the circuit.

 

Your codes indicate the various circuits in question, example being the knock sensor... gmupfitter has wiring diagrams. I would start at the actual sensor and follow the wire harness to where it terminates at the ECM, do the same for the other sensors/circuits. Eventually you'll find the fault, likely a common point where all the circuits having problems are near each other. 

 

[Coalkracker]

Great thank you! So this is definitely sounding like an issue with a wire or wires?

[asilverblazer]

It's where I would start with diagnosis.

 

If the wiring isn't a problem it could be an internal failure in the PCM. You should find that all the circuits with the issue terminate there. This failure would be far less common than a corrosion issue. 

 

In fact, I would start inspecting the wiring and connections there first. Unplug the connectors and carefully inspect. Also, inspect the under hood electrical center on the drivers side fender.

[Coalkracker]

Update, still no progress. I have been inspecting wires and connections and haven't found anything wrong yet. I cleaned the grounds, they were all clean already but cleaned them more just in case. I was messing around on my scanner and may or may not have some helpful info. I can see live data of all the sensors. If I clear codes while it is running it start running somewhat normal. Under fuel system status it will say "ECU 1 and ECU 2- closed loop, using oxygen sensor feedback to determine fuel mix". Then after a minute I hear that click with the constant "sound" or "slight noise" that I can't explain and ECU 1 and ECU 2 status goes to "open loop due to system failure". To me it sounds like it backs up the statement of being a wiring issue. But does that possibly narrow it down to where I need to look better?

[Coalkracker]

After doing some reading on open loop and closed loop I may be wrong with my previous statement

[asilverblazer]

1 hour ago, Coalkracker said:

If I clear codes while it is running it start running somewhat normal. Under fuel system status it will say "ECU 1 and ECU 2- closed loop, using oxygen sensor feedback to determine fuel mix". Then after a minute I hear that click with the constant "sound" or "slight noise" that I can't explain and ECU 1 and ECU 2 status goes to "open loop due to system failure". To me it sounds like it backs up the statement of being a wiring issue. But does that possibly narrow it down to where I need to look better?

What is happening is that the PCM is getting cleared of codes, signals for closed loop operation, runs through all its tests and reads all sensor data, sees an issue, triggering all the problems and back to open loop operation.

 

Check the main wiring harness through the firewall.

 

Are there new codes, or all the same ones (Particularly, are they still high voltage signal related)?

 

If you have traced the circuits for each of the codes from the sensor to PCM. Next step would be more careful and thorough diagnosis of each code/circuit. You would need to probe pins on individual connections of wiring to look for anomalies (where the presumably 12v is being introduced to the signal voltage).

 

Did you pull the under hood electrical center and look at the back side?

 

You could try unplugging individual items like the brake switch or starter relay to see if it has failed internally and could be shorting out other circuits.

 

I am still of the opinion that you need to be looking for a wiring issue where all these unrelated circuits come together in a location close to each other. The cruise switch, starter relay, evap valve, ignition coils, etc. are nowhere near nor related to each other. Some don't even enter the cabin, leaving the only common location as the PCM and under hood electrical center.