2004 trailblazer no crank no start

[Randall350]

Hello everyone,

I've recently come across a no crank no start on my '04 trailblazer. I have been reviewing several threads on here that go over this condition but I'm still stuck with no resolution. Below is what I have done to try and find the problem.

Tested the ignition switch with a test light and multi meter. Receiving 12 V battery power on all wires except for the yellow one when the key is in the accessory position ( key on ). When key is turned to crank/start the yellow wire receives 12V. From what I have been reading that is normal.

The instrument cluster acts completely normal during this, nothing looks at out of the ordinary to me when installing the key to turning to run.

Moved to the fuse block under the hood. checked for battery power on the ignition fuses. Power is available and the fuses are good ( checked with a multi meter and visual ). What I did find interesting is that the starter solenoid did not activate when I had a helper turn the key and I listen for the starter solenoid to click. Checked for power at the solenoid relay terminal 87 and 86. Both were receiving battery voltage. Figured the relay was bad, so I took some test leads and connected them to B+ and B- then connected the other end of the test leads B+ to pin 87 and B- to pin 85. You can here the relay change state so that checks out and is fine. Figured it may be a neutral safety switch that is giving me problems. Moving the gear selector into different positions and keeping my multi meter probed in to start relay socket 86, battery power would be present then taken away then back again as the selector was moved from park to drive then to neutral.

From what I can tell the starter relay isn't getting its ground reference from the PCM, to complete the circuit. I don't have a high dollar scan tool to perform and tests on the PCM to verify operation. So my question is, what tests can I perform on the PCM to verify operation of the PCM or is the PCM the problem and I should throw a new one on just to see what happens?

I've also jumped the starter motor contacts to verify it works and it cranks the engine over no problem.

Any help is greatly appreciated. I have attached a wiring diagram that I have been following to help assist with me trouble shooting.

 

[mrrsm]

Welcome to GMT Nation...

(1) Visit the Under-Hood Fuse Box and check the "Tightness" of the Four (4) Galvanized Post Bolts that hold the lower Harness Plugs. It would not hurt to Spray out both sides with CRC Electric Spray Solvent and let them all Air Dry before re-attaching and *Snugging* the sections back together:



(2) Visit THIS Link and read the Posts ...from Top to Bottom ... concerning "Grounds".

Electrical Ground locations

While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...

gmtnation.com

(3) If you can't get a good view of the Starter and Solenoid with a Bright Flashlight from a "Top Down View" over the Driver's Side Fender... Elevate the Vehicle and remove the Wheel. Then peel up the Rubber-Flap and examine the Starter Harness Connections though the Wheel Well. It goes without saying... But we never tire of saying this... "Place Jack Stands under the SUV for the sake of safety while performing your inspection."

(4) If you purchased the CRC Spray, Pull the Three PCM Connectors and give both sides a Good Spraying Out and allow them all to dry before re-installing and tightening them down.

(5) Suspicious Electrical Behavior should prompt looking carefully around the Motor for any signs of Rodent Feces, Dried Urine of signs of Nesting Materials or damaged Head-Liner... Wear Eye Protection, an N-95 Mask and a pair of M11 Nitrile Gloves while shining a Bright, Penetrating Light around all of the Harnessing looking for signs of Chewed Connectors or damaged wires and Harness Sheathing. Be Diligent...You won't be disappointed with making this effort.

(6) Don't ignore these precautions... The North American Deer Mouse is the carrier of The Deadly HANTA Virus that once inhaled, causes the Disease called "Hanta Pulmonary Syndrome" AKA "HPS" which is FATAL in nearly 40% of the cases for any folks unfortunate enough to inhale Infected Dust while cleaning up around the Rodent's confined Nesting and Defecation sites. Use ONLY Wet Rags soaked in Water with 5% Chlorine Bleach and Use NO Compressed Air to dislodge this material. There is No Cure and there are No Medical Treatments available to deal with "HPS" Infections:



(7) Raise the Driver's Side Rear Passenger Seat from the Nylon Tab between the Seat and the Bench Back and pull it towards the Driver's Seat Back. Then remove the Black Plastic Cover on the Second Fuse Box underneath... and carefully Probe ALL of the Fuses in there as well. Don't be too quick to replace a Burned Out Fuse without figuring out what the Circuit is that had a problem. Investigate that Circuitry for any obvious Shorts or Open Circuit issues from Wire Damage. On occasion, The "Green & Gold" Flexible cable in between the Fuse Block and the BCM Module will get damaged or covered with Liquids (Spilled Cokes) and cause issues this way, too. Be Suspicious, Thoughtful and Methodical.

(8) Is there anything installed in the SUV that is "After-Market" like a HUD or anything Odd in its Performance such as a Security System? Things can get *Pretty Wonky* from those items, too.

 

[Mooseman]

Welcome to the Nation fellow Randall. Not too many of us with that name

Your assertions on the schematic are correct. Have you tried starting it by turning the key to RUN and jumping the relay to crank it? Did you verify at the ignition switch that power to the other wires stays on while cranking? South Main Auto has had an instance where power to the pink wire would cut out when the key was turned to crank, effectively cutting power to the PCM.

Are you able to just run a code scan? Does the CEL come on when in RUN? If not, then either the PCM has no power or ground or the PCM itself is defective.

 

[Randall350]

Welcome to the Nation fellow Randall. Not too many of us with that name

Your assertions on the schematic are correct. Have you tried starting it by turning the key to RUN and jumping the relay to crank it? Did you verify at the ignition switch that power to the other wires stays on while cranking? South Main Auto has had an instance where power to the pink wire would cut out when the key was turned to crank, effectively cutting power to the PCM.

Are you able to just run a code scan? Does the CEL come on when in RUN? If not, then either the PCM has no power or ground or the PCM itself is defective.

Yes, I was able to verify that all powers stay on when the ignition was moved to crank. The only wire that losses voltage is the orange wire which from watching the video you posted I don't believe that is a problem and is most likely normal.

To answer your question about the CEL. I'm assuming you mean check engine light, if so the CEL comes on and stays on while the key is in crank or run position.

 

[Randall350]

Welcome to GMT Nation...

(1) Visit the Under-Hood Fuse Box and check the "Tightness" of the Four (4) Galvanized Post Bolts that hold the lower Harness Plugs. It would not hurt to Spray out both sides with CRC Electric Spray Solvent and let them all Air Dry before re-attaching and *Snugging* the sections back together:

View attachment 111036

(2) Visit THIS Link and read the Posts ...from Top to Bottom ... concerning "Grounds".

Electrical Ground locations

While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...

gmtnation.com

(3) If you can't get a good view of the Starter and Solenoid with a Bright Flashlight from a "Top Down View" over the Driver's Side Fender... Elevate the Vehicle and remove the Wheel. Then peel up the Rubber-Flap and examine the Starter Harness Connections though the Wheel Well. It goes without saying... But we never tire of saying this... "Place Jack Stands under the SUV for the sake of safety while performing your inspection."

(4) If you purchased the CRC Spray, Pull the Three PCM Connectors and give both sides a Good Spraying Out and allow them all to dry before re-installing and tightening them down.

(5) Suspicious Electrical Behavior should prompt looking carefully around the Motor for any signs of Rodent Feces, Dried Urine of signs of Nesting Materials or damaged Head-Liner... Wear Eye Protection, an N-95 Mask and a pair of M11 Nitrile Gloves while shining a Bright, Penetrating Light around all of the Harnessing looking for signs of Chewed Connectors or damaged wires and Harness Sheathing. Be Diligent...You won't be disappointed with making this effort.

(6) Don't ignore these precautions... The North American Deer Mouse is the carrier of The Deadly HANTA Virus that once inhaled, causes the Disease called "Hanta Pulmonary Syndrome" AKA "HPS" which is FATAL in nearly 40% of the cases for any folks unfortunate enough to inhale Infected Dust while cleaning up around the Rodent's confined Nesting and Defecation sites. Use ONLY Wet Rags soaked in Water with 5% Chlorine Bleach and Use NO Compressed Air to dislodge this material. There is No Cure and there are mo Medical Treatments available to deal with "HPS" Infections:

View attachment 111033View attachment 111034

(7) Raise the Driver's Side Rear Passenger Seat from the Nylon Tab between the Seat and the Bench Back and pull it towards the Driver's Seat Back. Then remove the Black Plastic Cover on the Second Fuse Box underneath... and carefully Probe ALL of the Fuses in there as well. Don't be too quick to replace a Burned Out Fuse without figuring out what the Circuit is that had a problem. Investigate that Circuitry for any obvious Shorts or Open Circuit issues from Wire Damage. On occasion, The "Green & Gold" Flexible cable in between the Fuse Block and the BCM Module will get damaged or covered with Liquids (Spilled Cokes) and cause issues this way, too. Be Suspicious, Thoughtful and Methodical.

(8) Is there anything installed in the SUV that is "After-Market" like a HUD or anything Odd in its Performance such as a Security System? Things can get *Pretty Wonky* from those items, too.

Thank you for providing the link to the ground locations. This will be really helpful when I start chasing down the grounds. I will report on what my findings are.

 

[Randall350]

Issue has been resolved. Found the Auto theft deterrent system was invalid and the computer need to relearn the passcode again. Once the passcode was relearned the vehicle started right up.

 

[mrrsm]

Yeah Baby! ...

 

[pell]

What is the relearn process? passcode?

 

[Mooseman]

huge problem after PCM update / calibration

i go to a local store for programing / tuning to update the pcm / calibrate , many friends done this before and got some good results , enhanced fan clutch , better ac at idle , less overheating due to enhancing the fan clutch response and many other results So the guy who handle the tech2 and...

gmtnation.com