• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

04 Won't crank

B

Bashby

New Member
Messages
7
Reaction score
0
Location
Charles Town, WV
I've been working on my brothers 04 6.6 trying to figure out this no crank situation. I found a wiring diagram and tested some things. It appears the ecm is getting a signal from the ignition switch and is not grounding the starter relay. I can manually ground the relay and it will crank but not start. I'm not sure if it's the PASS system or something else. With the key out of the ignition, the red led on the radio flashes every few seconds.
I think my next step is hooking up to a scanner to see what is going on. Is there a tuner or scanner I can buy that will allow me to view computer data to figure this out? Cheap is better but I'd like to hear any options. TIA for any help!
 
Actron makes a reasonably priced OBDII scanner. Is there a check engine light (MIL) on. If not then a scanner will do you no good.
AutoZone is one place to find the scanners.
 
WELCOME to the Forum! :welcome5:

I think some of the auto parts stores like Autozone will actually let you use a scanner for free. You may want to start there and then let us know what types of codes you have. Definitely check all of your grounds and be sure that the batteries are up to full power.
 
Thanks for the responses, guys. It does not have a CEL. I have some experience with Snap On scanners and what they are and are not capable of, but I have been out of the business for a few years. Would one of the Actron scanners be able to tell me why the computer isnt letting this thing turn over? I tried a pass system reset procedure but still nothing.
 
sounds like you need a ignition switch. pretty common item, i see quite a few at work. there pretty easy to replace, drop the lower half of the steering column trim and you turn the key to run position and can acess the tab to drop it down. if you look at your new one you will see what i mean. just make sure the new switch is in the same position when reinstalling
 
john65td said:
sounds like you need a ignition switch. pretty common item, i see quite a few at work. there pretty easy to replace, drop the lower half of the steering column trim and you turn the key to run position and can acess the tab to drop it down. if you look at your new one you will see what i mean. just make sure the new switch is in the same position when reinstalling
Click to expand...

But I am getting power from the ignition switch to the ecm.
 
Unless there is a CEL you won't read anything with a scanner unless it's a TechII (big $). I don't have any other suggestion at this point
 
another thing to check is the harness connectors on the drivers side of the engine for backed out terminals, and occasionaly critters make a home under the fuse box and chew on wires. undo the fuse block and check under it for broken or chewed wires. i'm just going through things i run into. check relays and fuses too. that red led on the radio is a theft thing for the radio if its a security issue a lock symbol appears in the dash
 
I did pull the fusebox up and checked for bad connections and what not. Swapped relays around also. I think it may need to go to the stealership. The lock symbol does not show on the dash display.
 
When you turn the key on does teh guages come on? Does the gear display pop up? Can you shift it out of gear with the key on and your foot not on the brake pedal?
 
Good thinking Ferm! It sounds like it could be a bad NSBU switch. They were a fairly common issue with that model year. The newer replacement switches are built much better as far as protection from the elements are concerned.
 
btfarm said:
The newer ones are internal (in the trans) IIRC
Click to expand...

06+ is internal, all 01-05's are external.

RI Chevy Silveradoman said:
Good thinking Ferm! It sounds like it could be a bad NSBU switch. They were a fairly common issue with that model year. The newer replacement switches are built much better as far as protection from the elements are concerned.
Click to expand...

04 is the single plug updated style that didn't give much trouble. The reason I asked is if there is no ignition power present to the ECM circuit, the shift interlock solenoid will not activate and prevent it from shifting out of park while the key is on without your foot on the brake pedal. If it does, that is a good indication there is no power present on the ignition circuit. 01-03 had the dual plug style NSBU that failed alot, the updated single plug unit came out mid year 03. The ignition switch is a dual sided switch, and it sounds like the ignition side isn't powering but the accesory side might be.
 
I'll have him check about the shift interlock. I'm pretty sure the gauges came on and did a sweep or something when the key was on, and did it again each time the key was turned to start and released.
 
NSBU - Neutral Start Back Up switch.

Taken directly from Merchant Automotive web site:

One of the most common problems with the Allison transmission is failure of the Neutral Start Back Up switch.

Some of the symptoms of failure include but are not limited to:

No start condition
Gear shift indicator on dash not following properly
Trans stuck in limp mode or fail safe
DTC's set indicating pressure switch codes

This switch easily installs with just common hand tools.

How does it work and why does it cause my transmission not to shift?


The vehicle is equipped with a column type shift selector. In addition to the column shifter, another component associated with the shift selector is the Nuetral Start Back Up (NSBU) switch mounted on the selector shaft of the transmission. The NSBU switch transmits selector position information to the TCM. The NSBU switch mounts directly onto the transmission housing, from the outside, and detects the angular position of the shift selector shaft. This position is communicated to the TCM so that certain vehicle control functions can be coordinated with the position of the shift controls. The neutral signal output of the NSBU switch is typically used as confirmation that the transmission is in NEUTRAL or PARK before the engine starter is engaged.
 
You must log in or register to reply here.
Back
Top