NEED HELP Wont start after engine swap

#1
HI all, I have an 03 tb ltz with the 4.2 i6. I threw a rod in the stock motor and opted to swap it out with a motor from a 05 tb ltz. After the swap (which was a complete pain in the ass) the transplant motor won't start. To be more accurate when I turn the key it does nothing. All lights work, as does the radio and accessories, but when I turn the key forward it does nothing at all. I also can't get the transmission to shift out of park. Any suggestions, pointers, advice etc would be greatly appreciated...
 

Locksmith

Silver Supporter
#2
Does it crank? Did you use the same pcm from the old motor?

Is it possible that you forgot to bolt on the engine ground straps, and the electrical circuit ground itself out through the shifter cable? That situation would cause the cable to spot weld itself, and the shifter cable to freeze up. Go underneath the blazer and make sure the cable is connected and not pinched or kinked, and that the transmission lever that connects to the cable is in the parked position. Another similar vehicle will help you determine if it is, indeed in the parked position! Hope it is a start!
PS As Mooseman suggested, there should be a selenoid that won't let you shift out of park if your brake pedal isn't completing a circuit when depressed. I had a bad brake lamp bulb in a 94 Lincoln Towncar that wouldn't let me shift out of park. Replaced the bulb, and everything was happy!
 
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#4
When you try to crank it, do you get the flashing "lock" icon in the dash? That would mean it needs a security relearn.
huge problem after PCM update / calibration (PCM Security Relearn)

With the ignition key in the Run position, do you hear/feel the shift interlock when you push on the brake pedal?

With both issues, pretty much sounds like a ground issue. Check all the fuses too.
 
#6
When you try to crank it, do you get the flashing "lock" icon in the dash? That would mean it needs a security relearn.
huge problem after PCM update / calibration (PCM Security Relearn)

With the ignition key in the Run position, do you hear/feel the shift interlock when you push on the brake pedal?

With both issues, pretty much sounds like a ground issue. Check all the fuses too.
The lock or security icon doesnt stay on, it'll flash then go off. And yes I can feel the shift interlock disengage when I depress the brake pedal. I've even tried starting with the transmission in neutral, but it still won't crank. It's acting as if the battery is dead, but i know the battery is good bc it's been hooked up to a charger/maintainer. I've checked and rechecked all the ground connections and have verified that none of the harness is kinked or pinched. Fuses have all been tested with a multimeter and were good....
Another thing I noticed is when I hook up the battery the battery light and the shift indicator in the dash both come on even with the key out and ignition in "off". Not sure if this problem is related or if I have 2 different gremlins..
 

Locksmith

Silver Supporter
#7
So the donor was proven to run before the swap? A freshly rebuilt motor will be hard to crank, as you probably already know. Imagine the joy when you find the reason! Don't give up!
 
#8
Have you tried to jump the starter relay socket to engage the starter? That would eliminate an issue with the starter motor itself.

For the shifter, try disconnecting the cable from the transmission to check if the cable is free and that the tranny can be shifted by hand.

This video is our go-to for diagnosing no crank:

 
#9
If the battery light (or any dash light) is on when the key is out, then you've also likely got an ignition switch failure, and that can cause all sorts of stupid problems. Very well could be related, or could be separate. But, might as well swap the switch while you're at it.
 
#10
***UPDATE***
Ok, first things first let me thank yall for the much needed input and guidance, THANK YOU :smile:
After taking yalls advice/leads and the video guidance via youtube, i was able to locate and remove a couple of kinks in this seemingly simple engine swap. I did have to reset the pcm for the key to work correctly; there were a couple of ground(negative) connections on the block where the terminal didnt line up correctly on the block that needed to be adjusted; the aluminum grounding strap had disintegrated at one of the terminal ends; the starter relay was toasted, as is the ignition switch. That being said all items have been fixed/replaced except for the ignition switch, which brings me to my next question: is there a work around to where i can wire in a push button or toggle switch or retinal scanner (jk) to start the trailblazer instead of forking out the cash for a new ignition? I have several different toggles at my disposal, hell i even have an old doorbell button that could be used if needed... all jokes aside i am serious about a toggle to bypass the ignition. Any leads, comments, suggestions etc would be greatly appreciated, thanks in advance
 
#11
So essentially, you want to hotwire it like in the movies with the magical wires you pull out under the dash? :biggrin:
It wouldn't work as the Passlock security will kick in and stop you.
The switch isn't too expensive or you could try cleaning it.
Rebuild you ignition switch
 
#12
An ignition switch is cheap. Maybe that's why they tend to fail...
 
#13
12 VOLT CONSTANT RED (+) @ IGNITION SWITCH HARNESS
STARTER YELLOW (+) @ IGNITION SWITCH HARNESS
IGNITION 1 PINK (+) @ IGNITION SWITCH HARNESS
IGNITION 2 WHITE (+) @ IGNITION SWITCH HARNESS
ACCESSORY/HEATER BLOWER 1 ORANGE (+) (MUST used BOTH ACCESSORY wires) @ IGNITION SWITCH HARNESS ACCESSORY/HEATER BLOWER 2 BROWN (+) (MUST used BOTH ACCESSORY wires @ IGNITION SWITCH HARNESS

You have to use both ignition wires but can't connect them together! So feed each one individually.(if you don't use both you get all sorts of transmission codes etc.)

Now the fun part,understanding the passlock 2 system:

https://kingbain.com/how-to-permanently-disable-gm-passlock-system/


Read it untill you understand it completely,it's really not that hard but wiring it wrong can cost you your BCM so be careful.

If you want a more simplified scematic let me know and I can draw one up for you.
 
#14
12 VOLT CONSTANT RED (+) @ IGNITION SWITCH HARNESS
STARTER YELLOW (+) @ IGNITION SWITCH HARNESS
IGNITION 1 PINK (+) @ IGNITION SWITCH HARNESS
IGNITION 2 WHITE (+) @ IGNITION SWITCH HARNESS
ACCESSORY/HEATER BLOWER 1 ORANGE (+) (MUST used BOTH ACCESSORY wires) @ IGNITION SWITCH HARNESS ACCESSORY/HEATER BLOWER 2 BROWN (+) (MUST used BOTH ACCESSORY wires @ IGNITION SWITCH HARNESS

You have to use both ignition wires but can't connect them together! So feed each one individually.(if you don't use both you get all sorts of transmission codes etc.)

Now the fun part,understanding the passlock 2 system:

https://kingbain.com/how-to-permanently-disable-gm-passlock-system/


Read it untill you understand it completely,it's really not that hard but wiring it wrong can cost you your BCM so be careful.

If you want a more simplified scematic let me know and I can draw one up for you.

Well hell ya I would love a schematic! You wouldnt happen to have any links or pdfs of the factory wiring schematic you could send me do you? They would be nice to have while i figure out this electrical gremlin. The links/files ive found online are all crappy copies that are blurry and hard tro read... And thanks for sharing this with me
 
#18
***UPDATE***

So I've finally gotten the motor to run, and it ran almost perfectly!! I still cant get the tb to start via the key, i had to "jump" the starter :sadcry: but hey at least i know the motor will run and didnt get jacked up sitting on an engine stand for 2 weeks waiting to get installed. Now on to the newest issue post motor swap: THE TRANSMISSION WONT EFFIN ENGAGE :Banghead::badday::explode:. Let me explain, for whatever reason my "mechanic" decided it would be easier to pull motor and trans instead of pulling just the motor. That being said he caught hell trying to get trans park neutral switch unplugged and cut the harness!! I know i was like WTF this mofo here cut my harness and now i'm gonna have to splice it all back together. Trust i was less than thrilled when i found out. That same night he cut the harness and pulled the motor he got tossed in the clink for unknown reasons (as of this post he is still incarcerated and yes i've put $$ on his books), and that's when i stepped in and took over the engine swap (as i had never done something of this magnitude and couldn't dedicate the time initially to do the swap. So i hired this highly recommended "mechanic" to do the work for me, which turns out was a stupid move on my part. So i've reinstalled the motor and transmission with the help of my 10 yr old son, and a retired army mechanic. the splices to the trans harness I did myself with the same gauge wire, butt splices, and an electric crimper, so i know the connections are SOLID. The shift lever will shift when the brake pedal is pressed and the button on the handle pressed as well. When i shift out of park the doors lock (i it set like that) and unlock when i place it back in park. The indicator on the dash functions and shows which gear the transmission is in, and i'm pretty sure its correct cause i've had to put the tb in neutral to push it out of the way for other projects, even though i cant get the shifter to shift all the way down to 1st gear. I'm wondering if the trans problem isn't the root cause of the no crank no start, hmmm... Please any advice or links to threads of this kind of problem greatly appreciated, cause if i don't get this sorted out something tells me there's gonna be a bonfire with the tb at the heart of it smh....
 

MRRSM

Lifetime VIP Supporter
#20
I think you will find this Thread quite helpful as the situation you presently face is identical to one the OP encountered in his event. Also... Keep in mind that there is a Third Connector located on the Passenger Side upper flange area of the 4L60E Transmission...it is an Oval 20 Pin Connector that communicates with the PCM... and if that "Pinch-Squeeze-Pull" plug has any damaged or stretched wires inside of the Harness or attaching to the Connector itself... then Transmission will not properly engage. At the very least... Look it over with a small mirror first... then gently unplug it... inspect it... and perform a careful 'Tug Test' on the individual wires and connection points and see what you can find:

https://gmtnation.com/forums/thread...-replacement-issues-solved.17907/#post-549685
 
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Capote

Platinum Supporter
#21
Why would he cut the harness....? That plug is one of the easiest ones to release and plug back in, not to mention it's easaily accessible. Sounds like a jackass who cuts corners, no pun intended.
 
#22
First the obvious: Is there oil in the transmission? Are there bolts connecting the flex plate to the torque converter?
thanks for the input and to answer your questions: yes to both; tranny fluid is at appropriate level, and bolts installed and torqued to specs.

I think you will find this Thread quite helpful as the situation you presently face is identical to one the OP encountered in his event. Also... Keep in mind that there is a Third Connector located on the Passenger Side upper flange area of the 4L60E Transmission...it is an Oval 20 Pin Connector that communicates with the PCM... and if that "Pinch-Squeeze-Pull" plug has any damaged or stretched wires inside of the Harness or attaching to the Connector itself... then Transmission will not properly engage. At the very least... Look it over with a small mirror first... then gently unplug it... inspect it... and perform a careful 'Tug Test' on the individual wires and connection points and see what you can find:

https://gmtnation.com/forums/thread...-replacement-issues-solved.17907/#post-549685
thanks for the link, ill check it out and will also check the oval connector on the passenger side of the transmission. It was a pain to plug back in so i know exactly which one you are talking about.
 
#23
Also forgot to ask this earlier, but in the 2 connectors that comprise the trans park safety switch there is a yellow wire in each of the connectors but neither is labeled. They are both the same gauge, and have NO markings differentiating them. So my question is does it matter which wire goes to what? I obviously didnt splice them all together but am wondering will it make a difference in transmission function? i dont want to undo the splice to redo them because the jackass who cut the harness didnt leave very long leads to work with and im leery of adding additional wire to the harness.
 
#24
It's quite possible to have the same coloured wires but have different functions. You's have to check the schematics.

Are there any codes? If it's an electrical issue, you would get a code(s) for it. And even if the tranny isn't connected at all, it goes into a default mode and works in first and second gear to get you out of trouble. It wouldn't very well but it would engage somewhat.

Check to see if you get good flow from the tranny cooler line. Look for the fluid flush thread on how to do this but only run it for a very short while to see if the pump is working.

Did this tranny work before the engine swap? Did you buy it with the dead engine? Maybe the tranny died and the PO over-revved the engine throwing the rod at the same time.
 
#25
It's quite possible to have the same coloured wires but have different functions. You's have to check the schematics.

Are there any codes? If it's an electrical issue, you would get a code(s) for it. And even if the tranny isn't connected at all, it goes into a default mode and works in first and second gear to get you out of trouble. It wouldn't very well but it would engage somewhat.

Check to see if you get good flow from the tranny cooler line. Look for the fluid flush thread on how to do this but only run it for a very short while to see if the pump is working.

Did this tranny work before the engine swap? Did you buy it with the dead engine? Maybe the tranny died and the PO over-revved the engine throwing the rod at the same time.
I figured out what the yellow wires do, they are for the shift indicator in the instrument cluster. i swapped them to see what would happen/change and i lost the indicator when i swapped them.
No there arent any codes, as a matter of fact, my obd2 scanner wont even connect. i only get the red power light to come on, the communication light never comes on nor does the bluetooth light; strangely enough i plug in the scanner into my mom's 05 tb lt and it works fine, and in my wifes caravan, my brothers tahoe, my old explorer, get my point? Scanner is functioning but not in my tb. Also noticed the service engine light is dimly lit/flickering. when i say dim its lighting up about 20% of full on and flickers non stop when motor is running...
Yes the tranny worked perfectly fine as it was the original tranny in my 03. i only swapped motors. I threw the rod in my stock motor, and trans was working fine up until the loud clunk and spray of oil from my motor as a chunk of aluminum was blown off the side of the block. The donor motor was out of an 05ltz that had been deemed "totaled" by my friends insurance company after enduring a rear end collision at 45 mph.
 
#26
Check the lighter fuse for the power to the OBD port. Strange about the CEL partially lit. There's something going on there.

Edit: saw you have power but no comms. Maybe the PCM is bad or the wiring?
 
#27
Check the lighter fuse for the power to the OBD port. Strange about the CEL partially lit. There's something going on there.

Edit: saw you have power but no comms. Maybe the PCM is bad or the wiring?
if the pcm was bad or had faulty wiring the tb wouldnt run right? i can get the tb to run if i jump the starter, and it runs great, no leaks, no misfire, no rough idle, nothing at all wrong with the engine functions. You have to listen for it when its running its sooo quiet. While underneath the tb yesterday i verified that the linkage is moving in correspondence to the shift lever. still not sure why it wont shift all the way down to 1st tho, at least the indicator stops at 2nd... gonna verify the trans lines are all plugged in correctly and in the correct locations. looks like i might wanna start stocking up on my smore supplies....
 
#28
I will have to check back at work tomorrow, but we had a customer put in a junkyard engine from a different year and then it would not start afterwards. Come to find out, the crank sensor and crank (exciter wheel) is different between a year breakpoint. NOt sure about the trans issues, Mine is an 03 LS 4L60 2WD, I can check the years it covers by part number application tomorrow.

also recheck your GROUNDS for the engine, that can cause some weird sheet

also, rereading again, ..... the PRNDL switch needs to be heated with heat gun to melt the glue holding the connectors into the switch body. Can be a bitch if you never done it before and don't know

read some more, IF the trans switch was removed from trans, it needs to be realigned. if you look at it, you can see the two bolt holes are oval allowing it to pivot.
 
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#29
I will have to check back at work tomorrow, but we had a customer put in a junkyard engine from a different year and then it would not start afterwards. Come to find out, the crank sensor and crank (exciter wheel) is different between a year breakpoint. NOt sure about the trans issues, Mine is an 03 LS 4L60 2WD, I can check the years it covers by part number application tomorrow.

also recheck your GROUNDS for the engine, that can cause some weird sheet

also, rereading again, ..... the PRNDL switch needs to be heated with heat gun to melt the glue holding the connectors into the switch body. Can be a bitch if you never done it before and don't know

read some more, IF the trans switch was removed from trans, it needs to be realigned. if you look at it, you can see the two bolt holes are oval allowing it to pivot.
Ok let me know what you find out about the crank/crank sensor, the transplant motor came out of an 05 lt 4l60e 2wd, and mine is an 03 ltz 4l60e 2wd. I was told that the 05 and 03 motor was identical, only difference is some kind of emissions valve on the passenger side of the block just above the exhaust manifold and below the air intake, 03 didnt have this valve or whatever it is and the 05's did. The transplant motor will run if i leave the key in the run position and jump the starter. it actually runs great! its much smoother and quieter than the original motor. As far as the tps switch and connectors, with a lot of patience and some flat tip screw drivers i was able to seperate the connectors from the switch body with out having to move or take off the switch, making it possible to add my butt splices and small segments of wire to the existing harness sitting at my work bench and not on my back underneath the tb...
 
#30
crank sprocket is the same up to 2007, crank changes in 2006. So if its it running and with no codes, that should all be fine. I'm at a loss for the communication OBD2 problem. Check Radio fuse?
 
#31
crank sprocket is the same up to 2007, crank changes in 2006. So if its it running and with no codes, that should all be fine. I'm at a loss for the communication OBD2 problem. Check Radio fuse?
Thanks for looking into and verifying that info @mntegra01 ... Radio(fuse) is good. Checked it with a multimeter.... i think im going to recheck and reterminate all the engine block grounds, possibly upsize and upgrade the wires while I'm at it..
 
#32
While you are at it, check all the harnesses and make sure no wires got pinched swapping the accessories over.
 
#33
Didnt see / couldnt find any pinched wires, and all of the grounds appeared to be terminated correctly. I did upgrade a couple of the grounds wired from the teeny 16 gauge stranded and 8 gauge stranded to 4 gauge copper stranded welding wire. Still no crank no start (it'll run when i jump the starter and have the key in the run position), and still can't figure outhat why trans is unresponsive....
 
#34
Still no crank no start (it'll run when i jump the starter and have the key in the run position),
I know you said you replaced the starter relay, but have you confirmed if a signal is getting to the starter relay to activate when the key is turned to the start position?

There could be a problem with your PCM if it's not telling the starter to fire when it should. :twocents:
 
#35
I know you said you replaced the starter relay, but have you confirmed if a signal is getting to the starter relay to activate when the key is turned to the start position?

There could be a problem with your PCM if it's not telling the starter to fire when it should. :twocents:
Yes, I've checked to see if signal is getting to relay to tell it to send juice to starter. And it was as of last week when I checked. If the pcm was bad my tb wouldnt run at all right?
 
#36
If the pcm was bad my tb wouldnt run at all right?
Not necessarily. Any number of functions that it controls could be affected, depending on how it's damaged.

When you jump the starter, are you just using wire in the relay socket? Have you confirmed the new relay itself is functioning properly?
 
#38
Not necessarily. Any number of functions that it controls could be affected, depending on how it's damaged.

When you jump the starter, are you just using wire in the relay socket? Have you confirmed the new relay itself is functioning properly?
No, im using a insulated metal crowbar to jump across the 3 bolts on the back of the solenoid, i have tried to jump it off at the fuse box by jumping across the relay, but i wasnt successful. I think is was a bad connection at the fuse box as i was using metal blades from a fuse that i deconstructed for this purpose...
 
#39
Check to see if you have 12v+ at the relay connectors. If not, then that's likely the cause if there is, then it could be a wiring issue between the relay and starter. Also check if the PCM is sending a ground signal to the relay when trying to start it.
 
#40
the starter relay was toasted
I think is was a bad connection at the fuse box
:undecided: Was the relay physically damaged, like burnt or melted? Or just tested bad as in no longer making the connections correctly when commanded?

You could possibly have damaged traces on the underside of the fuse block, if the relay showed physical damage