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Pete, GMC Technician
Category: GM
Satisfied Customers: 28803
Experience:  14 years GM dealership technician and training.
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GMC G3500 Van Savana 98 gmc G3500 ,driver said security light

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98 gmc G3500 ,driver said security light was on all day which i never new. That day I borrowed battery for an hour,reinstalled day vehicle won't start. Cranks and runs a sec. then dies. Just replace new passlock sensor on steering columm/key. Tried5 to 6 times tying to reprogram and relearn the pass code. As so doing this the security light never went off. Still no running engine. Pulled code p1626. Have you ever replaced thepasslock control module. I'm lost
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.


Code P1626 is a loss of communication with the vehicle theft deterrent module or system.

This can be caused by wiring connection faults or the theft system module itself.These can be fairly expensive in some cases to diagnose and locate the failure and if it ends up being the module at fault then it may need replaced.

There is a way to bypass this security system in this vehicle if you want,it costs allot less and you wouldn't have the security issues again,this will eliminate the fault you have.There is a by pass kit that is available to eliminate this security system.If you go to the website below they can get you this bypass assembly,very easy to install,comes with instructions and can take sometimes around an hour to do this.Click on the PRO VATS bypass on the left of the website screen to order the kit.Just copy the link below and paste it into your browser.

If you do not want to completely eliminate these problems and you want to keep the theft system working in this vehicle let me know and I can try to help diagnose the fault here.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
sounds great but I would like to try to fix it the right way. Sorry I didn't get to expain myself. My name is XXXXX XXXXX Im a fleet repair mechanic,so this is the first time ive ran into this problem. So I would like to find out how to fix it right and learn. As I said before I replaced the passlock key assembly in the steering columm,cleared any codes and then proceeded to recode the passlock and by doing so the security light never went off in this process. If you can run through the diagnosis that would be great. I will also look and that website to bypass it too. thanks Jeff
The website offers a way to bypass allot of the GM security systems to eliminate the security problems most of them have all of the time.

I can post the key learn in here to see if this will help and to make sure it was done properly if you want to start there.

Let me know,Thanks Pete!
Customer: replied 6 years ago.
the problem is i did the key relearn and still wont start/run. Did this process 5 times,got info from dealership to relearn it. The problem is the security light won't shut off in the process of the key relearn. In the dealership notes it says the light will go off in 10 to 12 minutes then turn off for 10 sec. then repeat this 2 more times. again the light never goes off and i left the ket on for 20mins each time.

You may have a fault with the pass lock control unit itself here,the theft relearn should have caused the security light to flash then stay on steady then shut off after 10 seconds.

Since this is not doing this this sounds like it may be a security issue here.The pass lock module is located under the dash just to the passenger side of the steering column,this could be the component at fault here.

But according to the code you have set here this is either a loose connection at the engine computer or pass lock control module or a failure or broken wiring to the engine control computer,this code doesn't suggest the pass lock control module being at fault but instead a possible engine computer theft circuit being at fault and that the engine computer may need replaced.

First they want you to install a scan tool and try to communicate with the engine computer,pass lock theft control module,and transfer case control module.

They want you to check the transfer case control module for a code U1192 (if this vehicle has awd or 4wd in it).

Then clear the code and turn off the vehicle,then turn it back on and if it sets again the engine computer should be replaced and programmed due to the theft circuit failure in it.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
so knowing of this problem if I bypass the passlock is this going to solve this issue cause now you said i might have an issue the pcm.
When I reviewed the fault code you have here,if you have 4wd or awd in this vehicle they want you to check the transfer case control unit with the scan tool for a U1192 being set.If this is awd or 4wd then you may have a failure in the data line due to a break in the wiring,shorted to ground or voltage or loose or damaged terminals at the engine computer or the theft control computer.

If you don't have 4wd or awd they want you to clear out the P1626 code with a scan tool then turn off the ignition then turn it back on to see if the P1626 code has set again.

If it has they want you to replace the engine computer,if it does not set again then the failure is intermittent but chances are since the vehicle is acting up now the code will reset and the fix is to replace the engine computer and program the computer as well as the theft system.

The by pass system should eliminate the fault with the security failure this vehicle is having as it will bypass the security system to allow the vehicle to start and run.

Other then this according to the diagnostics the above components are what need to be checked and or replaced to correct the problem here.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
do you have any diagrams of passlock sys. such as grounds,etc so i can trace the short. cause im ready to buy the controll passlock module.Jeff
I don't have any diagrams that I am able to post.

You can test pin #2 which should be a purple wire at the diagnostic connector where you plug your scan tool in at,test this for resistance to ground and voltage.

If this is o.k. then you can disconnect the computers (engine computer,and theft computer,the electronic brake control unit and transfer case computer if this vehicle is awd or 4wd) and then test the resistance from pin 2 the purple wire at the data link connector to pin #11 in connector c4 at the engine control computer for an open circuit,then test from the dlc pin 2 to terminal G at the electronic brake control module which is also a purple wire for open circuit,and terminal 15 at the theft computer for open to the dlc as well.

If an open is found in any of these then this wire needs repaired or a new wire spliced in as this is the communication and theft fault here.

If all of these are o.k. then most likely according to the diagnostics the engine computer needs replaced or the theft system bypassed.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
i was told talking to a gm tech here in town he had problems with the igition switch and sending power to the passlock system. Remember the security never shuts of even during cranking. Jeff
Yes,this could definitely be the fault here if the pass lock system isn't receiving voltage to it.

If you want info on how and where to test for voltage at this system let me know but I have had to replace some electronic ignition switches in these vehicles to fix similar problems and it may be possible this is the cause of the failure here.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
please send me info it cause i was going to the dealership to get the ignition switch which is $200.00. Thanks Jeff

Test for voltage at terminals B3 pink wire with the key in run and in the crank or start positions,if you do not have voltage here on this wire then most likely you do have a faulty electronic ignition switch that needs replaced.

There should also be voltage on the terminal B8 at the module which is an orange wire but this should have power on it at all times so it dos not run through the ignition switch.

Let me know what you come up with here,Thanks Pete!
Pete and 5 other GM Specialists are ready to help you
Customer: replied 6 years ago.

i had to take it to my friends shop who has a tech2 scanner and found there no communication in the passlock system so he ordered a module for it and it comes in tomm. wait and see.


Let me know how it turns out,Thanks Pete!
Customer: replied 6 years ago.
it was the passlock module
Thats great to hear you have it running again.Let me know if you need anything else.
Thanks Pete!