Swapping ECMs on a 98 with Passlock

[GM Guy]

Hey all,

Its ECM time on the bomber 98.

I was curious if anyone could give me some pointers on swapping ECMs on a 98 6.5L with passlock.

The Gm books are talking about programming the ECM. Is this back when the ECM would show up "blank" and needed programmed for the application?

I assumed as long as it was from a 98-00 F code automatic I would be able to swap with no programming needed.

This engine also has stuck open t-stats, so it does not get warm. If the ECM does not need programmed, will it still try to do the TDCO relearn and I will then need to get proper t-stats in it?

The Section in the book details the 3) 10 minute ignition on security relearns. I assume put a 10 amp battery charger on it, or should I put a 30 amp to maintain voltage? I dont want to fry the glow plugs, but I dont want to get the voltage too low and mess up the re-learn.

Any info appreciated,
Thanks!

 

[ak diesel driver]

Should only have to do the security relearn. TDCO is only set when commanded.

 

[JayTheCPA]

If you do need to go through the Passlock cycle, *DO NOT* put a charger on the batteries. Reasoning is (as noted) that not all glow plugs like the extra voltage. Better bet if concerned about battery health is to attach a spare / fully charged battery. I have done the spare battery trick a few times just-cause. From experience, sometimes the Passlock triggers and forces me to go through the cycles, and sometimes it lets me start the truck right away.

The truck might not shift properly if the ECT is too cool.

For the TDCO re-learn, Yes, you will want to manually trigger it as the incoming computer will likely have a different reference point for the IP than actual. If the stuck T-stats allow ECT to get up to 170*F, then the re-learn will trigger.

Toward swapping ECM's, for that year range, IIRC the ECM's code are interchangeable. Naturally, am sure Ferm will correct me if necessary

 

[Big T]

OK real world experience here. On my '99 I swap in an ECM from another '99 K2500 Suburban to pass smog every two years. That and I put back the GM Turbo and Vac pump and make sure they're working. I never had to KOKO it, or do anything to it. It just works and the truck performs like a stocker with a butt plug in it, but it cleans up the smoke on the throttle snap test and I pass smog. I had some concern that they would read the VIN # off the ECM (which would show a different truck), but I specifically watched them and they used a type of hand held bar code scanner to read the VIN # through the front window. Observing that eliminated the concern that I would have to get the VIN # flashed onto the stock (smog) ECM.

 

[ak diesel driver]

When I put in the PCM on my 99 I had to do the security part.

 

[THEFERMANATOR]

OK real world experience here. On my '99 I swap in an ECM from another '99 K2500 Suburban to pass smog every two years. That and I put back the GM Turbo and Vac pump and make sure they're working. I never had to KOKO it, or do anything to it. It just works and the truck performs like a stocker with a butt plug in it, but it cleans up the smoke on the throttle snap test and I pass smog. I had some concern that they would read the VIN # off the ECM (which would show a different truck), but I specifically watched them and they used a type of hand held bar code scanner to read the VIN # through the front window. Observing that eliminated the concern that I would have to get the VIN # flashed onto the stock (smog) ECM.

You don't have to do the learn because your VATD code is already stored in both ECM's. When you use a different ECM, you will mostlikely have to do the vats relearn unless you have a scanner that allows you to shorten the procedure to just 1 key cycle.

 

[Big T]

You don't have to do the learn because your VATD code is already stored in both ECM's. When you use a different ECM, you will mostlikely have to do the vats relearn unless you have a scanner that allows you to shorten the procedure to just 1 key cycle.

What's the VATD code?

 

[THEFERMANATOR]

What's the VATD code?

Vatd=vehicle anti theft device when you do the 3 10 mi ute key cycle learn, the vats module sends a code to the ecm, after it does the 3 cycles, the ecm takes the code and licks it in. Ifyou remove the ecm and putit back in, it doesn't matter because the code is still stored in it. You could have a stack of ecm's all learned to your vats module code, and they would all work so long as it's the code of your system stored in the ecm.

 

[GM Guy]

So the conclusion is that all I need to do is install the ECM, and do the passlock relearn and I should be good to go?

 

[GM Guy]

OK, it turned out pretty well, swapped ECM, did the (3) 10 minute key on cycles, and the P0606 code is gone, and it now responds properly with every turn of the key. I am still tracing IP issues, but I think we are now on the downhill slide of figuring this ol girl out.