Can this be done?
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=25327
Printed Date: July 29, 2025 at 1:51 PM
Topic: Can this be done?
Posted By: diesel6.5td
Subject: Can this be done?
Date Posted: January 26, 2004 at 9:06 PM
I have a 1997 1500 GMC 6.5TD and I want to put a ECM from a 1999-01 3/4 ton or 1 ton. But the only problem is that the 99-01 ECM is looking for the passlock II system and my 97 doesn't have all the passlock II equipment. So how can I bypass the passlock II system without changing the steering column and all the other passlock II equipment. Is there away to bypass the passlock II system right at the ECM without having to put all the required passlock II modules and wiring in.
Replies:
Posted By: technodigifreak
Date Posted: January 26, 2004 at 11:48 PM
this is what you need, either do the complete swap on the 99-01 ecu or do it the right way and install an aftermarket ecu (this will let you tune to your hearts content) https://www.motec.com/products/ecu/m800.htm motec makes quality stuff, this particular ecu is designed for use on chevy big blocks and small blocks ------------- Hot-Modder
Posted By: diesel6.5td
Date Posted: January 27, 2004 at 12:50 AM
This is a Diesel 6.5L so that will not work I can get a reflash but this cost about $700 where the 99-01 ECM is about $150
Posted By: technodigifreak
Date Posted: January 27, 2004 at 8:24 PM
my bad i was thinking of the 6.3L HD engine as long as the trucks are in the same generation it should be a direct swap, make sure you use the newer modules instead of trying to bypass them ------------- Hot-Modder
Posted By: diesel6.5td
Date Posted: January 27, 2004 at 8:50 PM
is there away I can just do the ECM swap without changing anything else and just bypassing the passlock right at the ECM? ------------- 1997 GMC 1500 4X4 Ext Cab 6.5 Turbo Diesel
Posted By: technodigifreak
Date Posted: January 28, 2004 at 12:02 AM
not that i know of, you might want to make friends with an electrician at the stealership or lay your hands on a factory service manual with wiring specs ------------- Hot-Modder
Posted By: geotexz71
Date Posted: January 28, 2004 at 12:39 AM
You can have the Passlock programmed out of the GM ECM/PCM by an aftermarket reprogrammer. Dealers cannot do it as GM does not give them anything behind programming packets for the Tech II. I don't know why you want to go through the trouble of this swap for the TD as all of the 6.5L TD from 96+ use the same 588 PCM, except in 98 they got Passlock II and there were some programming changes for the transmission. Nonetheless, this is your choice, but here are the two largest, most well-known GM reprogrammers:
https://www.fastchip.com
- ask for Ed Wright
https://www.ecmprogrammer.com
- ask for Lyndon
These guys also work on the GM gear, but are more orientied to the gas motors so I don't know off-hand if they have the software for the TD:
https://www.hotrodlane.cc
- ask for Dean
https://www.speedscenewiring.com
https://www.centechwire.com
Unfortunately, you cannot do a hardwire bypass at the PCM because it really isn't the logic center for the Passlock II. That's handled by the EVO/Passlock module tucked up in the instrument panel on trucks with it. With it missing, bypass isn't possible as that communicates with the PCM via serial comm. HTH!
Posted By: diesel6.5td
Date Posted: January 28, 2004 at 3:42 AM
Geotexz71 The fuel rate on the 96-98 ECM is 63mm3 195 hp and on the 99-01 HD ECM the fuel rate is alot higher 76mm3 215 hp this is the fuel map that most reprogrammers use. so if I can use a 99-01 HD ECM it would cost about $150 but to get a reprogram it would be like $600 and more. but thanks for the info I will lock into this ------------- 1997 GMC 1500 4X4 Ext Cab 6.5 Turbo Diesel
Posted By: diesel6.5td
Date Posted: January 28, 2004 at 1:13 PM
ok if i just install the 99-01 ECM and the passlock II module but not the steering column can I make it work? ------------- 1997 GMC 1500 4X4 Ext Cab 6.5 Turbo Diesel
Posted By: geotexz71
Date Posted: January 28, 2004 at 2:16 PM
It been a long time since I worked anything on the OBS TDs, and without digging through my archives for the schematics, I'd say it's going to be near impossible and a major job to accomplish. The EVO/Passlock module needs the feedback resistance from the Passlock sensor in the ignition lock cylinder. You won't be able to do a direct column swap either due to differences in the harnesses, and I believe 97 was the last year for the older air bag...
Aside, there are also other differences in the later computer/programming that might present more obstacles, such as the misfire detection added in 98, they may need to be addressed too. Also you have to watch if you have an automatic transmission as changes were made physically and programming adapted to suite, but I don't remember the break points of the changes.
Like I said, it's been a long time since I worked the OBS diesels. Because of your unique goal, I would encourage you to at least call Lyndon Wester as he is very well versed and won't mind discussing it with you so you get the most accurate answer possible. Perhaps he will work you a deal just to remove the few road blocks versus his power tuning. Lyndon is a good guy and tells it like it is...
Posted By: diesel6.5td
Date Posted: January 28, 2004 at 2:39 PM
Thank you very much geotexz71 for all your help
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1997 GMC 1500 4X4 Ext Cab 6.5 Turbo Diesel
Posted By: diesel6.5td
Date Posted: January 28, 2004 at 6:22 PM
well i called and Lyndon and I are going to work some thing out. thanks guys for your help ------------- 1997 GMC 1500 4X4 Ext Cab 6.5 Turbo Diesel
Posted By: geotexz71
Date Posted: January 28, 2004 at 8:16 PM
Good deal! Like I said, Lyndon is a good guy!
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