you covered most everything I want to learn from what you do

 

right now I want pour gas all over it and set it on fire. lol
After work I buying a good soldering Iron and removing the 2 splice ground points and runnig a ground to the fenders. then taking the passenger seat out and sanding and wire brushing the 2 grounds under the seat. may get a new key cut also for the truck to see if that helps.
What is most frustrating about the situation is that it is probably something simple that I am going to accidently figure out.

 

Have you verified fuel pressure at the rail? Good plan to get all the grounds confirmed first. eliminate that concern.

 

Start with the basics. Put your old ECU back in and check for spark, fuel, air, compression. Passlock, when activated, will allow the engine to crank but it will turn off the injectors.

If no fuel pressure at the rail, check the fuel filter since you have an early model with one.

If no spark, check coil pack grounding locations, battery to body ground, engine to battery ground, all fuses and continuity from the ECU to the coils

If no compression, LS swap it.

 

we put the old pcm monday when we were checking everything with hp tuner. same situations as new pcm. Nothing happens when you turn the key. The dash lights up all the dummy lights and when you hear what sounds like a relay click but starter doesnt move nothing happens.
I may have to trailer it to my cousins shop to check fuel rail preassure and they have a spark indicator tool that goes between a plug and wire.

 

I'm assuming you tested the battery? The click is likely the start relay meaning the ECU is doing what its supposed to. You can check voltage to the signal wire on the starter solenoid. You could also try jumping the solenoid on the starter manually to see if it will turn over. This sounds more and more like a grounding issue. I'd double check the big grounds while you're down by the starter. There's one on the lower left side of the motor by the starter that goes to the battery. There's also one between the battery and brake booster on top of the inner fender. You could try "The Big 3" while youre in there and just piggyback over the existing grounds with 2 or 4 gauge wire in case there's corrosion inside the factory wires themselves.

 

I checked the 2 grounds on the block battery side removed and cleaned them with sandpaper. Then same to the one between battery and brake booster, 3 on the transmission I cleaned one had the loop break off so I soldered a wire onto it and mounted it to the one between the battery and booster, removed the passenger seat and cleaned the 2 under the carpet, and I also disassembledthe splice packs sanded all the prongs put wires back on and soldered the connectors to the prongs and checked resistant with multimeter and sanded fenders when reconnecting.

 

Yes checked the battery its ok not new but ok been keeping a charger on it as I work on it. We popped the covers off the starter relay and 2 other ones to make sure they were engaging and working and not fused together . We also engaged the starter relay and the starter engaged and rolled over but it is as if it isnt getting fire, or fuel is what it sounds like to me.

 

When it turns over, will it run on starting fluid? That will split the dictionary between spark and fuel.

 

Hi did you by chance try the original pcm again after clearing the codes ? Or did you just go directly to replace it 🤔

 

Yes tried it then I got the new one tried it then tried the old one after a few tries. Contacted flagship one about the new one they had me return the PCM so they can check that it was programmed correctly. So currently waiting to hear back or have it shipped back.

 

I had to replace my ECU/PCM when it was having troubles on cold days, and one day just stopped being able to run. There were codes indicative of ECU/PCM problems. Thankful there are online services that can ship to door a reprogrammed unit to cure this.

 

Ok got my 2nd PCM in on Friday. Installed it battery was drained down to 5v so I replaced it and the fuel pump.

As of now I have:
1.Checked/cleaned grounds
2.Soldered ground splitters and checked resistance
3.Replaced the PCM 2x
4.Replaced sensor on ignition switch
5.Checked all fuses
6.moved relays around
7.starter is good
8.plug in and unplugged bcm to make sure contacts were in good shape
9. New fuel filter

Still rolls over but no ignition. Won't let it roll over after the first attempt. So I wait about 10mins and it will let me try to start it again

I'm about to spray some starter fluid into the throttle body to see if it hits a lick.

 

Decided to just buy a fuel line pressure kit at harbor freight.
I'm getting about 25psi which isn't enough but after I try it once I still have to unhook the battery for 10mins touch positive and negative cable together then hook battery backup to get it to crank a second time. Something is locking out the ignition. I've been looking at bcm.

Is bcm the next step? Can I test the bcm? Bcm is discontinued of course I can get a used one wait for it to ship then send it to be cloned. Any suggestions on who to go to for bcm reprogramming?

 

You should be getting around 58 psi at prime, and 42 while running on the fuel pressure. 25 is too low. You are correct.
What is the result when you shoot starting fluid into the TB and crank it?
I don't have any good ideas on the 10 minute crank lockout. That is strange behavior.

 

My gut tells me that the ignition switch is either telling the bcm the wrong thing which could activate the demobilizing system which would explain the low fuel pressure and explain cutting of access to the starter after the first try. I may try replacing the entire switch cylinder just to rule it out since I already bought it to rob the sensor off it. Then if it still doesn't work it's probably the bcm. Does this make sense or am I chasing ghost

 

The passlock system only disables the injectors, not the fuel pump or starting circuit. It won't have an effect on fuel pressure.

I'd figure out whats wrong with fuel before going any further. You may have a stuck injector, or bad pump.

 

Yeah, there seems to be 2 issues. One is that it wont start when it does crank. Then there is the no crank on the 2nd attempt issue. Issue 1 needs to be killed first, IMO. To get after that we need to know if the truck has timing and spark, and its a fuel delivery issue. Starting fluid into the TB will tell us that.
If it will not run even on fluid, then we may be looking at spark. Or worst case, a timing failure.

The clue we have of the 25 psi is sticking out to me right now.

@SpikeG is right, the demobilizer would not cut the crank circuit or fuel pump. It only kills the power to the injectors. and you get the flashing passlock indicator.

If we can get the truck willing to run when it cranks, then we can get after why it wont crank a second time. Sarter solenoid or ground maybe... We will burn that bridge if we get to it.

 

If the injectors are stuck open, the fuel pump would be filling the cylinders with key-on. This would account for the low pressure and could cause a no-fire condition followed by no-crank due to hydrolocking. Waiting 15 min would allow the fuel to drain past the piston rings or evaporate enough to fire again.

Would be easy to check by pulling the spark plugs and looking in the cyl with key on (preferably with a borescope).

If the hydrolocking isn't the source of the second no-crank, you should do a crank position relearn after the fuel issue is fixed, as that'd the only electrical thing I could think of preventing a second start.

 

The crank position relearn is one of the codes I'm getting but I can't get it running to do the crank relearn procedure?

 

All the bcm stuff says history so I'm not sure if that is an issue or not but I figured it was. I was going to try and get some starter fluid into the throttle body see if it would fire but it's shut and I don't want to try and force it open. The throttle body was replaced about 2yrs ago with AutoZone aftermarket one they had available. I'm just starting to get a little tarnish on the aluminum so I don't think it is gummed up.

 

I'd still start by finding out why you have low fuel pressure. If you have known issues, nothing else can be done with any degree of certainty.

After that, if you still have a no start a few things to try:

The throttle body should be cleaned with every oil change, the idle air control has small passageways that clog easily with oil/carbon from the PCV system. A clogged IAC port would cause the initial rough running an no-fire condition. Ideally you'd use an OEM replacement as well. I'm unsure if a bad throttle body would tell the ECU to disable the starting circuit, I'd imagine not but the codes you have indicate a failure there.

The BCM controls the starting circuit and the low voltage code would be an issue. The headlight short to + may be an issue as well. Are your headlights stuck on high beams? You can pull relay 47 to see if it helps anything, also check the voltage to the BCM ang G105 :

 

Hi everyone,
My 2005 colorado started throwing codes like crazy. I will list the codes below. One day I ran back in the house to grab something and came back out and the truck was idling really rough. So i shut it off and when I went to restart it nothing no crank or start. I looked back through the codes and saw pcm failed suggested repair replace pcm. So thats what I thought I needed to do. Got the new pcm installed did the manual passlock relearn and still nothing but the passlock dash light was on solid no blink. So I thought maybe the sensor on the ignition cylinder was bad so I bought a new cylinder and robbed the sensor and replaced it (i didnt know if mine was a wheel lock or not i just grabbed what they had instock locally). Did the relearn and still nothing well within the few hundred times of trying the passlock relearn it would crank but not start but after that nothing would happen. so at this point i called my cousin who runs a street rod shop and had him bring his mac tool obd2 scanner over and just do the passlock relearn. We reprogrammed the key fob and but still couldnt get it to start.
Monday my cousin brought his laptop with HP Tuner and we cleared all codes. Shut VATs off to take it out of the equation. He opened the relays and made sure they were all working. we could manually operate the relays and and get it to crank but couldnt get it to start. I am currently talking to flagship one where I got the new programmed pcm and I am also in the process of checking all my grounds and fuses. We checked the connectors on the pcm by unplugging and plugging them back in and notice when we do this it allows it to crank but not start once but it does nothing after that one time unless we unplug it again. dash is showing reduced power still after pcm maybe because we havent been able to relearn crank position.

Any suggestion welcome! luckly someone in the familu had an extra car but this truck is my day to day and I dont know what to do next. im mentally exhausted on this one please help.

Last few weeks of codes before and at point of its death:
p2101, P0606, P060D, P060E, C0055, U1016 BCM, U1016 SIR, P0607, P2119, P0315, P2101, U1301, U1000, B2960, U1000

SO finally its fixed not sure anything I did helped but I endup taking it to my cousins street rod shop and had his mechanic look it over. They put a new GM throttle body on the truck and it started right up. They said the throttle plate on the autozone throttle body I had purchased had jambed itself shut and would not open. This was causing it to roll over the first time after the passlock was relearned but then the pcm realized the throttle position was off and shut it down.
Im just glad its alive again.

 

SO finally its fixed not sure anything I did helped but I endup taking it to my cousins street rod shop and had his mechanic look it over. They put a new GM throttle body on the truck and it started right up. They said the throttle plate on the autozone throttle body I had purchased had jambed itself shut and would not open. This was causing it to roll over the first time after the passlock was relearned but then the pcm realized the throttle position was off and shut it down.
Im just glad its alive again.

 

Thanks for following up! Great information here in case someone else encounters these same symptoms and codes. Im sorry you went through so much chasing down that bad TB, but Im glad it worked out in the end.
Hopefully it will run trouble free for you for a long time now. You did a lot of good PM work in the process.