03 LB7 security light
- Thread starter lutzjk913
- Start date
Ok, here's something from the FSM. Connect your Tech2. Turn the truck ON, momentarily rotate the ignition switch to the START position but let it return to ON before the truck can start. Scan the BCM for DTCs. Check the Passlock Data Voltage, as in the screenshot above, needs to fall between 0.86 and 4.28 volts. Also, the Passlock Code should be a number between 1 and 10. If the Passlock Code continues to say "Open", you have an issue with a connection or with your Passlock sensor itself in the key lock cylinder.
Sorry to hear that, what a bummer. Glad to hear the $$ is coming back in.
part of life man.
We got through it and its behind us.
eventually I’ll get it figured out.
@dndj
I did as you suggested and I do get a valid code and the voltage is slightly below the cutoff (4.25). Could that voltage be too close to the cutoff for it?
I also started the truck afterwards and looked for any changes between the two screens and the only difference I noticed was VCM/PCM Fuel continue is off when the truck is not running, and is on when the truck is running. I've included a screen shot of the data while the truck is off.
I did as you suggested and I do get a valid code and the voltage is slightly below the cutoff (4.25). Could that voltage be too close to the cutoff for it?
I also started the truck afterwards and looked for any changes between the two screens and the only difference I noticed was VCM/PCM Fuel continue is off when the truck is not running, and is on when the truck is running. I've included a screen shot of the data while the truck is off.
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Interesting. Your passlock sensor voltage is in range and there's a valid code so it would seem logical to look elsewhere.
Do the same thing, rotate to crank and release to ON position before vehicle starts, scan for DTCs. Look for ECM DTCs (including history DTCs) and BCM DTCs (also take a look at history codes). Reading BCM DTCs requires navigating down the Body menus on the Tech2 instead of Powertrain, I think.
VTD "fail enabled" means the VTD detected an electrical issue while the vehicle was running but won't activate and cause the no-start condition as it would in a true lock cylinder tampering theft situation. There should be a stored DTC for this somewhere. If not, I'm out of ideas. Doing an ECM-BCM password relearn procedure requires the truck to be in a VTD no-start condition so that wouldn't be an option. I had this exact same failure (security light ON, but truck runs) and ended up sending my ECM off for repair at SoCal diesel. Whatever magic they did worked.
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