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P1626 Code
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Post P1626 Code 
I have a 2000 GMC Yukon Denali. My truck has been periodically not starting in the mornings. Then after trying it again that night or next day it starts without any problems. I took it into an auto repair shop and the mechanic told me it had two codes P1626 (fuel enable circuit) and P0161 (02 sensor) and that P0161 is probably an old code. He also stated that only GMC or shops with a Tech 2 device could diagnosis the problem to fix. I called GMC and they wouldn't tell me what part is bad. I can't afford any more major repairs especially at the GMC rates. Please help!

Single parent of two Sad

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Responded to your PM. Did some digging and found some of the old info when I was looking into this myself. Here is a screenshot of the VATS code I pulled out of the 99 Tahoe I was having this problem on:



As far as this being retrievable with a Tech-II only, I find that unlikely, as I was able to pull the code with my AutoTap scanner software (read: ancient OBD-II scanner, there are way better programs out there now). ABS codes usually cannot be read with a run of the mill scanner like this, and usually anything out of a module separate form the VCM (separate ABS module, body module, etc.). Long story short, any AutoZone could probably pull this code for free. As far as fixing it, it's just a matter of replacing the worn VATS parts which are basically a sensor in the ignition switch and an actual module in the dash. You could do some diagnosis to find out which one is the main culprit, but the 99 Tahoe got both parts replaced at the same time, as both parts do fail. There is nothing else required as far as the computer is concerned, as in you do not need a Tech-II to program in the new VATS parts or anything like that. You may have to do a VATS relearn procedure, but that's it. Below is a link to a .pdf that explains how to do the relearn procedures, and if I recall, it was the following section from that page that I used on the 99 Tahoe:

http://www.bsecorp.com/files/techtips/ST9303l.pdf

1. First, insert the ignition key and
turn the ignition switch to the
“On” position (Do not start the
engine). Leave the switch on for
11 minutes. The security light
may flash or be on steady during
this 11 minute period. Make sure
the light is no longer on or
flashing before proceeding to #2 .
2. Turn the ignition switch off for 30
seconds.
3. Turn the ignition switch to the
“On” position (as in step #1) for
11 minutes again.
4. Turn the ignition switch off for
another 30 seconds.
5. Turn the ignition switch to the
“On” position for 11 minutes a
third time.
6. Turn the ignition switch off for 30
seconds one final time.
7. Turn the ignition switch to the
“On” position one final time and
wait 30 seconds.
8. Attempt to start the engine.
If the engine starts and runs
normally, the relearn is
complete.


Normally, I would have part numbers for those VATS parts, but I don't this time. They are a dealership only item, but try and get a part number for them and shop around at places like GM Parts Direct or P&G.

One other option is to have this feature programmed out of the computer entirely, meaning you will not have to replace these parts and this will never pop up again. This is custom programming and the computer would have to be sent off (or traded for one they ship to you) to someone who does that sort of thing (i.e., FastChip in Oklahoma to name one place). There my be places local to you who can do this. Up to you whether or not retaining the VATS feature is worth it.

Hope this info will be enough to get you started.

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Is there an aftermarket alarm system installed on the truck?

DTC P1626

CIRCUIT DESCRIPTION
The control module communicates with other modules using the Class 2 Serial Data circuit. The vehicle theft deterrent (VTD) body control module (BCM) sends a vehicle security password to the powertrain control module (PCM), via the Class 2 Serial Data circuit, after the BCM has sensed the proper operation of the ignition switch and lock, and determined that the switch and lock have not been tampered with. If this password matches the password stored in the PCM, fuel will be enabled. If the BCM does not send a password, or if the PCM does not receive it, the vehicle will not start, or it may start and stall. This will set a DTC P1626 in the PCM memory. If communication is lost after receiving the password, the VTD Passlock system will go into Fail Enable, set a U1192 in the PCM memory, and the engine will continue to run. This will allow the engine to restart on future ignition cycles but may set a DTC P1626 as the engine is started. If the battery is disconnected or the codes are cleared, the vehicle will lose its Fail Enable status and will not start until communication is re-established.

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 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 diagnostic trouble code (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 ten minute timer expires, and the PCM receives the correct fuel delivery password.

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Just had somthing real similar on a 2001 pontiac grand am. Long story short I had to replace the ignition switch. That part cost me $250 and about an hours worth of time. The ignition switch has the integrated PassLock or vats in it. Hopes this helps....

TJ

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98Blackss wrote:
Just had somthing real similar on a 2001 pontiac grand am. Long story short I had to replace the ignition switch. That part cost me $250 and about an hours worth of time. The ignition switch has the integrated PassLock or vats in it. Hopes this helps....

TJ


I believe what you replaced was the ignition LOCK CYLINDER,not the ignition switch.The PassLock is part of the cylinder,not the switch.

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Yes, there are three parts in the Pontiac grand am. In the Pontiac there is a plastic housing which included the electrical switch and P/N interlock that the cylinder and cylinder housing (that has the passlock Hall-effect sensor in it).

Just make sure you replace both the lock cylinder (the part the key goes into) AND the cylinder housing. The lock cylinder rotates in the cylinder housing. Over time the rotations cause wear of the pot metal and the microscopic metal particles interfere with the Hall Effect passlock sensor.

You can take out the lock cylinder assembly, clean the old grease and metal filings off, grease, and reinstall. This should work 90% of the time. My original lasted 150K miles, and I elected to replace the parts so I would not have to mess with it ever again since I had to take apart the majority of the dash.

I believe in Pooh's case the cylinder is in the column and may involve more/ different disassembly. If you have to remove the steering wheel, airbag etc., I would definitely make sure the repair wouldn't need to be addressed again for a long time.
TJ

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Post vats Switch 
Anyone have part number for this item? 1999 C-k1500 4x4 5.7 vortec old body style.

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Post code p1631 
Does anyone know what wires do what coming out of ignition switch? I think there is a certain ohm reading the vats sends to pcm to let the truck start?

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Put a multimeter across your key and see what the resistance is.

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playtoy_18 wrote:
Put a multimeter across your key and see what the resistance is.


that one does not have the resistor key - its in the lock cylinder - if that is messed up, not sure how you would get the correct resistance value. i used to bypass them all the time for remote starts, but it had to be working in order to get the value.

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