How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Jerry Newton Your Own Question
Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 4829
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
Type Your GM Question Here...
Jerry Newton is online now
A new question is answered every 9 seconds

1998 chevrolet s10 blazer: passlock..bcm and the Ignition wiring

Resolved Question:

i have a 1998 chevrolet s10 blazer. i am having passlock issues and its not letting the blazer run. I have replaced the BCM and the Ignition wiring. and treid the relearn process but still nothing. what else is there i nthe system that would cause this. i have had it on a scanner during the process changes and it keeps bringing up the code that says incorrect code, but valid
Submitted: 5 years ago.
Category: GM
Expert:  Jerry Newton replied 5 years ago.
If your code is "valid but incorrect" then the relearn isn't being performed correctly. You have to be patient with the relearn process, it can be quirky and cumbersome.

Tell me how you relearned it.
Customer: replied 5 years ago.

i turned key to forward position, stayed there until the security like shut off 10 mins. then turned key to off position for 10 seconds then back to on position, this time security light did not come on, but i let sit for 10 mins before turning key to off position. then tried starting. would start for 2 seconds then shut off with security light blinking . so i tried re learning it again, left key in on position until light quit flashing, then it stayed on solid, after 2 min it shut off. then urned key to off position for 10 seconds and then forward to on position again. again no security light on second try so tried to start. still same results 2sec runing then shut down, checked computer again and came up with same code.

Expert:  Jerry Newton replied 5 years ago.
Interesting that there's no security light on the 2nd attempt.

You replaced the BCM. What did you replace it with, and who programmed it? BCM's must be programmed to the vehicle, they won't work off the shelf.
Customer: replied 5 years ago.

i picked up a second BCM at local salvage yard from what they said and contacting the local gm dealer said they didnt think it owuld need to be programmed, my old BCM however would not communicate with the scanner.

Expert:  Jerry Newton replied 5 years ago.
OK. That may or may not be true, but at least you're getting some communication on the scan tool.

Let's go over the procedure from GM, and see if we can get this going for you:

30 Minute Procedure

1. Ensure that the battery is fully charged.
2. Use a scan tool in order to clear the Passlock™ DTCs.
3. Turn the ignition switch from the OFF position to the CRANK position, and then to the RUN position.
The vehicle will start and then stall.
4. Leave the ignition ON until the security telltale turns OFF in 10 minutes.
5. Repeat Steps 3–5 for 2 more times (3 times total)
6. The Passlock™ controller will learn the new data on the next start attempt.
7. Use a scan tool in order to clear all DTCs.
Customer: replied 5 years ago.
so do i need to re install my original BCM or use the one i have?
Expert:  Jerry Newton replied 5 years ago.
Use the one you have, since it communicates with the scan tool and is at least giving you valid trouble codes. It's just telling you that it's not programmed, I think we need to be a little more patient with the relearn process, and it will come together for you.

The BCM programming may have other issues down the road, as these trucks came equipped with different options, and the programming was different based on the options (keyless entry, foglights, etc.). But programming shouldn't affect engine starting, except that the replacement BCM has to learn the code from the existing Passlock sensor, using the technique above.
Jerry Newton and 3 other GM Specialists are ready to help you