Pass Lock light on dash - Chevy and GMC Duramax Diesel Forum
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post #1 of 15 (permalink) Old 01-02-2011, 10:17 AM Thread Starter
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Pass Lock light on dash

Hey all, been following on the site for some time now, never posted anything since I cant give any useful knowledge like everyone else on here. Anyways, i have an 04 LB7, the pass lock light has been on on the dash for quite some time, never stopped it from firing up or anything like that, but it's really starting to annoy me. Anyone have any idea how to shut it off? Thanks in advance

04 2500hd lt duramax/allison 4x4 ext. cab short bed
lt 285/75/16's
4" turbo back, cold air intake, bullydog tuner
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post #2 of 15 (permalink) Old 01-02-2011, 04:59 PM Thread Starter
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anyone?

04 2500hd lt duramax/allison 4x4 ext. cab short bed
lt 285/75/16's
4" turbo back, cold air intake, bullydog tuner
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post #3 of 15 (permalink) Old 01-02-2011, 05:09 PM
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DTC P1631

CIRCUIT DESCRIPTION
The class 2 serial data circuit is used in order to communicate between the powertrain control module (PCM) and the vehicle theft deterrent (VTD) body control module (BCM) systems.

When the Passlock portion of the VTD system has sensed the proper operation of the ignition switch and lock, or determined that the switch and lock have not been tampered with, the BCM transmits a password to the PCM. Fuel delivery is enabled if this password matches the password stored in the modules memory. If a component in the theft deterrent system has been replaced, the modules need to relearn the password of the new components. If the relearn procedure was not performed, this DTC will set.

If a VTD failure occurs during an ignition cycle that the PCM has enabled fuel, then the BCM will enter a fail-safe mode: Fail Enable VTD System Failure with Fuel Enabled. The BCM remains in Fail Enable Mode, for the current and future ignition cycles, until the fault is corrected and a valid password is received, or until battery power is removed. If the battery is disconnected or the codes are cleared, the vehicle will lose its Fail Enable status and will not start until the fault is corrected, the 10-minute timer expires, and the PCM receives the correct fuel delivery password.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P1631 Theft Deterrent Fuel Enable Signal Not Correct

IMPORTANT: Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame and Failure Records data.



•If the PCM is replaced, the PCM must re-learn a valid password and crankshaft variation.
•If the BCM is replaced, the PCM must re-learn a valid password.
•Check for published service bulletins relating to exhibited symptoms or component operation.
•If the vehicle does not start, or starts and stalls:
•Turn OFF the ignition and wait at least 5 seconds before trying to restart.
•If a fault or tamper has been detected, the BCM will not forward the correct password to the PCM for a period of 10 minutes , even if the condition is corrected during that time period. This may cause a DTC P1631 to set in the PCM. This timer can be monitored in the Passlock Data parameter of the scan tool. Once the time has elapsed, the BCM will determine if the condition is still present.
•The PCM and BCM parameters can be monitored with a scan tool.
•The Passlock state and the auto learn timer can be viewed in the Passlock Data parameter of the scan tool.
•Inspect the following for preventing the Passlock sensor from communicating with the BCM:
•Passlock sensor
•Ignition switch assembly
•Passlock sensor circuitry
•Bent pins at the small Passlock sensor
•If this DTC sets along with a DTC B2960, then the problem was caused by malfunctioning Passlock components or circuitry, not the PCM.
•Inspect all related wiring and connections including the PCM and BCM connections. These may cause an intermittent malfunction.
•An intermittent may be caused by any of the following conditions:
•A poor connection
•Rubbed through wire insulation
•A broken wire inside the insulation
•Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint.

Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.
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post #4 of 15 (permalink) Old 01-02-2011, 05:15 PM Thread Starter
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thats one hell of a write up, so basically i should start by checking all the wiring under the dash, make sure nothing was compromised, and go from there?

04 2500hd lt duramax/allison 4x4 ext. cab short bed
lt 285/75/16's
4" turbo back, cold air intake, bullydog tuner
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post #5 of 15 (permalink) Old 01-02-2011, 05:35 PM
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Ha Ha , I had it saved from someone else- does give you some reading and understanding how it works. To cold out anyway! Here is the relearn--
30 Minute Learn Procedure
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON; the vehicle will not start.
Observe the SECURITY telltale; after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes; the vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.

Important
The vehicle learns the Passlock Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.


Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.
With a scan tool, clear any DTCs, if needed. History DTCs will self clear after 100 ignition cycles.



--------------------------------------------------------------------------------

After replacing the ignition switch...

Turn the key and attempt to start the car, it won't. It should just crank once.
Wait 10 minutes. The passlock light should be flashing and the DIC will say "Service Vehicle" during that 10 minute span.
After 10 minutes has passed, turn off the car, count to 10, and try to start it again.
Wait another 10 minutes.
After 10 minutes, turn car off 10 seconds and try to start again.
Wait another 10 minutes.
After 10 minutes, turn car off 10 seconds and try to start again.
It should start up this time. The passlock has been learned.

Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.
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post #6 of 15 (permalink) Old 01-02-2011, 05:41 PM Thread Starter
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I'll have to try the key cycle thing soon, I tried it once in the past but it didn't work, iprobably did bit wrong, thanks for the help, ill keep you updated once I try it

04 2500hd lt duramax/allison 4x4 ext. cab short bed
lt 285/75/16's
4" turbo back, cold air intake, bullydog tuner
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post #7 of 15 (permalink) Old 01-03-2011, 06:11 PM Thread Starter
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tried the 30 minutes procedure, waited about 15 minutes for the light to go off with key in the on position, never happened...any other ideas??

04 2500hd lt duramax/allison 4x4 ext. cab short bed
lt 285/75/16's
4" turbo back, cold air intake, bullydog tuner
fournier126 is offline  
post #8 of 15 (permalink) Old 09-11-2014, 02:31 PM
 
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Why my 2008 chevy duramax keep blowing a dlis fuse
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post #9 of 15 (permalink) Old 01-27-2020, 06:56 AM
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My 2007.5 new body Duramax (same as 2008) also keeps blowing the 2 amp dlis fuse. Chamuco, did you ever figure this out? Mine just started doing this.
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post #10 of 15 (permalink) Old 01-27-2020, 10:14 AM
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Ron Nielson
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