2002 trailblazer 4.2L no crank

#1
i have a no crank issue.
to start the battery is good , the starter is good and i have to supply power to the purple signal wire going to the starter or jump the wires 86 to 30 on the starter relay socket in order to start the truck. after reading the schematic on the starting system, when you attempt to start the vehicle, it should receive a ground signal from the pcm(starter enable relay control). i am not getting a signal to that socket on the starter relay. also , the crank fuse should activate as well when attempting to start the vehicle. i am getting nothing there. I am also not getting anything out of the yellow wire on the ignition switch which is going to the crank fuse, which is a good fuse.
Any help will greatly be appreciated because i also have a 06 monte carlo with the same issue and i had to start it with a manual switch
thanks all
 

I_Shoot_Back

Well-Known Member
#5
I am also not getting anything out of the yellow wire on the ignition switch which is going to the crank fuse, which is a good fuse.
Was reading too fast,sry. That statement makes the ignition switch prime suspect,that is if you do see 12 volt on the red wires going into the switch.
 
#8
i installed the new oem ignition switch and i'm having the same result. also when i turn on the ignition i hear a rattling sound under the dash. funny because the monte carlo i have is having the same no crank issue and it also has a rattling under the dash.
hmmnn......
 
#9
That could be the sound of the gauge stepper motors cycling.

So you have a no crank issue. One thing that is a possibility is the VATS that has gone wonky. Is the security padlock light on or flashing?

For some reason, the PCM is not happy and not wanting to send that signal to the starter relay. One of the main reasons is a bad park/neutral switch or it's not adjusted properly. It's on the transmission. What is the PRNDL indicator showing?
 
#10
no security light on. actually no lights on dash.
the PRNDL is working correct according to the display on the dash. even when i put it in park the doors unlock. so idk
i am not getting a signal to the starter relay when the car is attempting to crank. i have to jump the relay or the signal wire on the starter
 

budwich

Well-Known Member
#14
you need to back up. first how are you checking the fuse... with your eyes or meter? Second what FUSES have you checked (22, 34 shows in the schematic). Along with checking said fuses, check the voltage conditions in the fuse block to see whats there. Lastly, what wires at the ignition have you checked for voltage? Lucky you the a "pair of evil twins"... that way when you resolve the issue with one, the other gets "his" for free... :smile:
 
#16
And nothing at the yellow? One of two possibilities. You got a bum ignition switch (it has happened if not an ACDelco) or the teeth are off. What if you jumpered from the red to yellow wires with the ignition on? Does it crank?
 

budwich

Well-Known Member
#19
providing power to the yellow doesn't do much IF there is no ground supplied by the PCM for the relay to pull up. :-(

have you checked the fuses that were suggested... not sure how 28 came up... its not involved in the schematics???????
 
#20
providing power to the yellow doesn't do much IF there is no ground supplied by the PCM for the relay to pull up. :-(

have you checked the fuses that were suggested... not sure how 28 came up... its not involved in the schematics???????
i've checked the fuses. theyre good. and i also put a jumper wire on the red to the yellow with the ignition on and still will not crank
 
#22
so the last question is... how did you check for the ground? IF that check was done at the relay socket... then you need to actually continuity check from the socket to the pcm connector to ensure that you have a wire path for the ground to get there.
 

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