Need help with snag.....

[docgreen9]

Ok, swapping a 2004 silverado 5.3 w/4l60e trans into an 89 gmc truck. My problem I'm seeing it the tow/haul switch and the air conditioning. Mainly the interfaces these two have with the PCM. The tow/haul goes through the body control module and the a/c uses the HVAC control module ( the switches ). The trouble is they don't connect to the PCM directly. Seems these two and a lot more all communicate through the serial data bus ( OBDII connector ). Short of getting all these modules out of the donar truck is there a way around this? Wanted to know if anyone else has ran into this trouble. I'm thinking if I could find out what the serial signals are from both of them I could build some sort of interface that would convert an analog signal ( switch or other item ) into the correct digital communication to the PCM?? Just a thought. If anyone has an thoughts please let me know. I have a schematic of both systems if someone needs to look at them. Thanks.

[bud8fan]

did you get all the wire harnes and pcm from the '04...if not ...thats what you need to do to make it a simple swap...

[RedHeartbeat]

Don't use the 5.3 a/c controls from the harness, just wire it into your factory harness. Do you really need the tow/haul switching? Disable it and run one standard setting. You shouldn't need all the BCM stuff from the donor truck. You should be able to disable all the unnecessary stuff and run the bare essentials by programming it out of the PCM. You can disable error codes that would be output to the SES light.

[docgreen9]

bud8fan, yes I got the harness all the way up to the firewall and the pedal assembly. but I didn't get the body control module under the dash which works with the tow/haul switch along with every other electrical device on the truck.

Red, yea I was leaning to just wiring the ac up with out the computer but I was just worried about the idle up it does when the ac is on. On the tow haul... yea I need it this truck tows a boat just about every weekend. I have to double check but I don't think the silverados shifter has the option for taking it out of overdrive. I think it just has PRD21 I think.... Thanks for your replies. Let me know if you have any other thoughts.

[RedHeartbeat]

I just pull mine into drive, not overdrive, when trailering. No problems.

[docgreen9]

Thanks Red for the info. I was going to head to the chevy dealer today at lunch to do a R&D test drive... lol. That solves that problem then and as far as the A/C I'll wire around it and make it work. Thanks agian for the help

[Tydriver]

Originally posted by RedHeartbeat@Feb 20 2005, 06:12 PM
Don't use the 5.3 a/c controls from the harness, just wire it into your factory harness. Do you really need the tow/haul switching? Disable it and run one standard setting. You shouldn't need all the BCM stuff from the donor truck. You should be able to disable all the unnecessary stuff and run the bare essentials by programming it out of the PCM. You can disable error codes that would be output to the SES light.

I find the comment about disabling it from the PCM interesting, I am going to be attempting to address this issue very soon as I am installing an LS1 in my '92 Typhoon.

Since I havent been exposed to the "NEWER" stuff that much I am not really all that familiar with what I would need inorder to 'talk' to the PCM, I realize some sort of software and a laptop but what is required on the TRUCK side of the equation?

Is the BCM required to make contact with the PCM ???
Other than a scrapyard, any idea where I can get a OBD-II plug ? (The Typhoon is not even OBD-I, it has an ALDL port)

I have a complete Engine, Harness and PCM from a wrecked '00 Camaro SS thats going in and I'd really like to know what I am going to need other than the harness and PCM to talk to the stock LS1 PCM...

Any additional information would be great. Sorry DOCGREEN9 not trying to hijack your thread or anything, it just seemed like a good time to chime in and ask..

Thanks in advance !

[RedHeartbeat]

If you put the pcm and wiring harness in the truck you're talking. To program the PCM you can either buy yourself a copy of LS1Edit or HPTuners and do it yourself or simply have Allen program a PCM for you with free updates for life. Red wires from the harness are power 24/7 and pink wires are switched. Get you a wiring diagram and go to town on the harness.

[docgreen9]

Red thanks. I'm way ahead of ya... lol. Yea I already got all the schematics on cd. Allen has already shipped me my pcm back should have it today.(yea) I've been thinking about purchasing LS1 edit or silmilar software. I appreciated all the information and your assistance. Thanks! I will post a link to pics of it soon probably when we are done with it.