I haven't seen any metal on the top of the fuse it's all encased unless there is something I've been overlooking with everything else that is going on.
SOLVED! Trailblazer not starting please help
- Thread starter MBS1994
- Start date
I didn't think of that. I can try and see if the local store rents them out. Sorry to everyone that's trying to help. It's been a very busy time for me and that's why it even took two months to even try and start troubleshooting this problem. I appreciate each and every input and will try all of them as time allows.
my statement is EXACTLY true... re-read it if you must. Your problem "symptom" is that you have NO CHECK ENGINE light on when the key is ON and the engine is not running. This has nothing to do with the battery light.... and actually that is probably not true... your battery light should not be on unless you have a battery issue and it has drained down to below a certain voltage or otherwise.
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I just meant because in the past to clear codes tripping the check engine light I have disconnected and reconnected the battery before and that would usually have the check engine light go away for a few days of driving. I just got confused at first not thinking about just sitting at ON/RUN it should be illuminated and then would go away after it starts assuming there was no code present. Oh and battery might be a drained down some now seeing as I've been messing with it for a few days with it not starting to charge the battery.
Blckshdw
Moderator
There should be 2 small exposed sections on the top of the fuse, where you can put the leads of a multi meter (or a test light) to check for voltage on either side of the fuse.
no problem... your "drained down some"... is drained down a lot. This condition will not help your no start problem. You always need to be very clear on what you say or indicate that you see as you are our "internet eyes and ears"... we are blind without concise observations. That's why the pictures are good as that leaves little to misinterpretation. Hopefully, you will get this resolved but its looking more "muddy". Your initial post implies a "ignition switch issue"... you need to check out the states of the ignition to ensure that battery shows up at the expected points as indicated in the schematic. IF they are wrong, you will likely never get a valid start condition from the PCM.... but you may be able to hire a car thieve on a temporary basis to "work around" the situation... 
Maybe I was thinking of just the starter relay/fuse when
17 lights at crank with my test light.
Very fair point. I'll have to get something to check actual voltage and try that. I'm getting to the point I thought to hire a car auctioneer or a wreckerno problem... your "drained down some"... is drained down a lot. This condition will not help your no start problem. You always need to be very clear on what you say or indicate that you see as you are our "internet eyes and ears"... we are blind without concise observations. That's why the pictures are good as that leaves little to misinterpretation. Hopefully, you will get this resolved but its looking more "muddy". Your initial post implies a "ignition switch issue"... you need to check out the states of the ignition to ensure that battery shows up at the expected points as indicated in the schematic. IF they are wrong, you will likely never get a valid start condition from the PCM.... but you may be able to hire a car thieve on a temporary basis to "work around" the situation...
How about a little history.....before it was parked 2 or more months ago...how long did you have this truck and how well did it start then? I think you said you experienced random no crank issues. Is this why it was put aside? And did you have this truck for a good while before that or had you just gotten it? And any particular reason you suspected the security system was an issue and thus you sent it to PCMofNC??
I had it for maybe 5 months at that point. It previously had been sitting on farmland for who knows how long. The only issue I ever had was I would try to start it sometimes and nothing would happen but then I could turn it back to off and it would start up, that was fairly regular. It was worse before it was parked and then last i remember i could only get it to start once and for the last time by disconnecting the battery and reattaching it. I suspected it because the padlock and no crank no start. Once I got the ecu back that's when i did more reading and tried replacing the switch
Mooseman
Moderator
You're likely pretty frustrated right now but I think good progress has been made. You've confirmed the 12 volt signal from the battery through the ign A fuse, on to the ignition switch where you checked and confirmed the right signals there. In the start position you followed that 12 volts down the yellow wire to the crank fuse. You can see the path of this signal in the wiring diagram. This is exactly how electrical troubleshooting should be done, follow the circuit. From the crank fuse that signal goes to the PCM or ECM. When you got your ECM back and you reconnected the connectors to the ECM did you check the pins to be sure they were all straight and looking good?
That circuit we just spoke of is just one of a couple (or more) that are needed to start. Remember a Pink wire at the ignition switch? That wire goes through the ign E fuse down to the transmission where it goes through the park/neutral switch and comes back to the fuse box under the hood. There it connects to, you guessed it, the starter relay. If that doesn't get 12 volts there that starter relay won't work when the ECM grounds the other end of it. That no crank starter video may have touched on this. When the key is in RUN (or start) there should be 2 sockets at the starter relay that have 12 volts. When you did the jumper test did you check for 12 volts at the various pin sockets for the starter relay? There needs to be 2 that light the test light.
That circuit we just spoke of is just one of a couple (or more) that are needed to start. Remember a Pink wire at the ignition switch? That wire goes through the ign E fuse down to the transmission where it goes through the park/neutral switch and comes back to the fuse box under the hood. There it connects to, you guessed it, the starter relay. If that doesn't get 12 volts there that starter relay won't work when the ECM grounds the other end of it. That no crank starter video may have touched on this. When the key is in RUN (or start) there should be 2 sockets at the starter relay that have 12 volts. When you did the jumper test did you check for 12 volts at the various pin sockets for the starter relay? There needs to be 2 that light the test light.
Insanely frustrated. I did not check the pins but on the ecu and harness. I will go check after work and a few more circuits. Is there any way to just pin point the security system locking it out? Would the current paths just die at the ecu as far as the diagrams go?
Just checked starter relay and two light up on run
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Mooseman
Moderator
The VATS killing starting the engine would not affect any other circuit. The PCM gets a go ahead signal from the BCM when it sees all is good with security and the PCM sends the ground signal to the starter relay.
Have you checked with a scanner if you can talk with the PCM?
Have you checked with a scanner if you can talk with the PCM?
No not yet. I just got off for the day and still need to study for a epa test. I'm going to go and check a few more things on the electrical. I'm hoping to get a cheap scanner this week though
OK then, that says the park/neutral switch looks good. Those 2, the park/neutral and the ECM side of the crank fuse need to get to the ECM.
Edit: I circled the wrong wires in the previously post image
I'm an HVAC Journeyman
So am I wrong for thinking ECU? In that starter relay he was able to get a ground request in a socket and I do not and i think someone mentioned that comes from the ecu? Or I just suck at reading these diagrams.OK then, that says the park/neutral switch looks good. Those 2, the park/neutral and the ECM side of the crank fuse need to get to the ECM.
View attachment 91342
I'm an HVAC Journeyman
I was a HVAC apprentice for a little bit and liked it
What exactly do you mean here..."ground request". And if possible can you identify exactly what terminal ## are you referring to with this "ground request"?
Both pairs are diagonally opposite each other on the relay.
#87 & #30 are the relay contact set that sends 12 volts down to the starter solenoid in the starter motor. These are the ones you put the jumper wire in. On one of those 2 sockets you should have a path to ground through the starter solenoid and the other will have 12 volts at all times.
# 85 and #86 are the relay coil. These should have 12 volts at one of them if the transmission is in park or neutral and the key is in RUN or START. And the other one goes to the ECM. I think that one would read as an open circuit unless the ECM is grounding it as it is supposed to do in START.
The reason I am concentrating on these circuits is that these are things you can test with your test light. If all this tests OK then what you are left with is BCM (security issue) or as @Mooseman suggests, a communications issue.
The lack of a check engine light is troubling, particularly if you are certain that it used to work.
I'd have to check the sockets again tomorrow but in that video you shared everything does exact as him except for when I check for the ground
I had to just rewatch that video while you were posting! I see what you mean now. It had been a long time since I watched that. So if you are not getting the ground from the ECM when the key is in START (test light hooked to battery positive and the relay socket in question) that leaves...
{A} the ECM or
{B} the connections (wire & pins at each end) that goes from the relay socket to the ECM or
{C} a security issue. The ECM needs an OK from the BCM before it will ground that terminal.
So where my ecu had always been fine, never had a check engine light not hang around, I could have not plug the ecu in proper? Or the security wasn't properly deleted (nothing against pcmofnc, they've been great and already said they are more than happy to check it again), or both. Not being properly plugged in could explain the possible lack of communication right?
I haven't seen this myself but I'm fairly sure I've read where folks have had ECM connection pins get bent and not make proper connections.
What I have experienced is bad connections between relays and fuses and the fuseblock itself. My TrailBlazer had intermittent no crank issues for the first year or so that I owned it. It turned out to be several bad connections at the fuseblock crank fuse, starter relay, and the starter itself. I think the fuseblock connection problems were the result of a previous owner jamming stuff down in those sockets. My fuseblock diagram in the cover came to me with the crank fuse and something else circled! Was glad when I finally got that straightened out. Several times the security locked me out and I had to just leave it for a half hour or so then it would start.
What I have experienced is bad connections between relays and fuses and the fuseblock itself. My TrailBlazer had intermittent no crank issues for the first year or so that I owned it. It turned out to be several bad connections at the fuseblock crank fuse, starter relay, and the starter itself. I think the fuseblock connection problems were the result of a previous owner jamming stuff down in those sockets. My fuseblock diagram in the cover came to me with the crank fuse and something else circled! Was glad when I finally got that straightened out. Several times the security locked me out and I had to just leave it for a half hour or so then it would start.
What would be most helpful is know PRECISELY what was done to the ECM with regard to security
The fuses and relays I pulled didn't seem like there was any damage in the sockets and I definitely haven't crammed anything in them. I'll have to check the connections tomorrow. The ecu only cam be plugged in one way right? No way I could have plugged one in on the wrong part right?
I will call them tomorrow and see if they can email me something or at least provide details.
I didn't see the damage in my fuseblock either. It's tough for old eyes to see down in there anyway. But with circuit testing using a multimeter I could see at times the connections were not solid.
I actually do no know if the connections can be swapped but I would highly doubt that.
I tagged someone there several posts back in this thread hoping for some enlightenment. Still dark where I am 😂
You aren't going to get any start action unless your PCM is happy (that light needs to be on)... that is the indication that the PCM has coms and is happy... so looking at the start circuit is putting the cart before the horse.
I'm really thinking part of my problem is maybe the harness isn't plugged in proper or there is a bad connection. I dont think it's a coincidence that it's my first time doing something with the ecu and now it's not communicating. Is there something I can use to clean the connection point of the ecu and harness assuming its dirty?
could be... since the history is "dubious"... meaning you don't know exactly what the previous owner user did or did not do.... but it is unlikely since you had a start issue BEFORE touching the PCM. It is more likely a powering / switch issue which again needs to be totally checked electrically. tjbaker already posted the circuit for the switch. I know its not the easiest thing to get at but without fully checking its "states" out, you are not going to move forward very far.
Having said that, do you know if any one played with the BCM module? No I am not suggesting you start playing with it.
NOTE: the switch doesn't need to be connected / install to test it... use a resistance check between pins (ie. input power pin to any pin) ... mark where the switch position is as a reference so you know where you came from and where you are going. Without moving anything, you should be able to tell what the current state of the switch is (ie. accessory, lock, run, etc)... this is the TEST of your understand of the diagram, the switch and system.
Having said that, do you know if any one played with the BCM module? No I am not suggesting you start playing with it.
NOTE: the switch doesn't need to be connected / install to test it... use a resistance check between pins (ie. input power pin to any pin) ... mark where the switch position is as a reference so you know where you came from and where you are going. Without moving anything, you should be able to tell what the current state of the switch is (ie. accessory, lock, run, etc)... this is the TEST of your understand of the diagram, the switch and system.
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Way back in Post #7 you heard Fuel Pump run. Then later you don't hear it anymore. What about now? Reason I ask this is the Fuel Pump is energized by the ECM in the same manner as the starter relay. If the fuel pump is priming at first key turn to ON then the ECM is at the least powering up and can close a relay.
Ignition switch was tested fully in Post #75
Not to suggest a retest is not a good idea... that's the trouble with intermitents, they come and go !!
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No I dont think anyone messed with it. The people who had it before me were a old couple so I doubt either of them would mess with anything and instead take it to a mechanic plus it had been just sitting for a while, can't remember If he mentioned how long. The switch is good now it has power everywhere it should. Could the previous starting issues have been the switch and now since the ecu isn't seeming to communicate I either didn't hook it up right or maybe something went wrong in the tuning or both?
No I dont hear it and even now I'm questioning if I convinced myself I heard it or maybe something happened shortly after that's now causing it not to power up
well I don't consider that testing of the states of the switch... that's checking a couple of wires at some point. Anyway, this is not an intermitent. This vehicle currently can not be made to start at all, at any current time and the system status are NOT correct and things have been "played" with. I certainly hope this vehicle gets running reliably.Ignition switch was tested fully in Post #75
Not to suggest a retest is not a good idea... that's the trouble with intermitents, they come and go !!
Further note that the check at the switch is only one point of many paths that have to checked to ensure that what's at the switch gets to those who need it when they need it.
where have you tested and shown this????? From this llloooonnng drawn out thread you have never stated / confirmed that you have power on the orange when in run.... the quote of tjbaker, i believe is wrong or does not line up with the posted diagram.... this should have been highlighted accordingly. This is one example. There are others.
Please disregard the post... I apologise for my poor reading skills.
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I went through with the switch diagram TJ provided and they all lit up my test light in the correct ignition positions
It cranks! One of those clips wasn't fully pulled so it wasn't seated. It has a check engine light at run now. Still dont have a fuel pump noise