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Ok guys I have an LM7 out of a 99 Silverado to put into my 05 Silverado W/T that had a 4.3. I managed to get the motor dropped in (new motor mounts, etc), Transmission bolted up and torque converter to Flexplate is bolted up and Good to go. Now my issues are with the wiring. I got the full wiring harness with the 5.3 but I don’t see how it connects to the transmission. After running the wires to the computer and the fuse block - There is a plug (block) from the motor (has 8 wires) that does not connect to the OEM truck plug (block) which also happens to have 8 wires as well. I will try to upload pics for you all to see. But I just don’t see how it plugs to the trans. The old (V6) motor wiring had the transmission wires integrated into the motor harness. Hopefully the pics will load up for you all to see. Because I am lost as to how to proceed and need some guidance as this was not covered in the multiple motor swap how-to. What is this connection for? What is this connection for? Fuse block - rewired properly. I think. I mean there is only one way that those blocks went back into the fuse box. Motor bay as it currently sits I guess this is the fuel “return” line? Transmission connection (OEM V6) harness Another view of the V6 connection.
I believe, the plug in your hand goes to the rear body harness that runs along the frame up to the fuse box. Connection might be under the fuse block in the plastic tray.
The broken part on the front of the intake is Vacuum Solenoid for the Evap system.
The broken sensor in the rear of the intake, under the cowel, is the map sensor.
As for your wiring on the 99 it used a 2 piece plug to connect to the range switch. Not a 1 piece like shown on the 2005 V6 side...
As posted you'll need a 03+ harness. If you can't find one from an Express van to retain the cable throttle system you'll need an electronic accelerator pedal and TAC module (drive by wire). If the clips that hold down the MAP sensor are broken on the intake you can use the "cruise control bracket" (also holds down the engine cover part number 12561510) to hold down that sensor ($7 ebay)... pic below
I believe, the plug in your hand goes to the rear body harness that runs along the frame up to the fuse box. Connection might be under the fuse block in the plastic tray.
The broken part on the front of the intake is Vacuum Solenoid for the Evap system.
The broken sensor in the rear of the intake, under the cowel, is the map sensor.
As for your wiring on the 99 it used a 2 piece plug to connect to the range switch. Not a 1 piece like shown on the 2005 V6 side...
WOW - How could you tell from that pic that the Vacuum Solenoid and the Map Sensors were broken??? like I said this is all new to me so I am learning the hard way - Trial by Fire! Thanks for the help. About the rear body harness - I will get back under the fuse box and look to see if they plug in there but I did not see any more open slots that would accommodate those 2 plugs. again I could be wrong - I will report back.
Originally Posted by 1FastBrick
I was at a junkyard today and that plug is a different color on the 03-07 classic.
A 99-02 harness will not bolt in and function properly in a 03-07 classic truck. It will require repining to make it work properly.
In my opinion it's best to get a 03-up harness and wire it for a cable throttle body like used on the Vans.
I dont have the pinouts for the required changes but that seems the easiest route to me.
ARE YOU FVCKIN KIDDING ME!!!!!!!!!!!
I'm kinda pissed now because the whole reason for me looking for a DBC motor was because it was "Supposedly" Plug n play from one GMT truck to another and now this issue with the Harness. Nowhere and I mean nowhere was there a mention of the difference of the 99-02 harness to the 03-07 trucks. DAMN DAMN DAMN!!!! I've had my truck down long enough as it is and need to get it back up and running. Sorry to Vent just I thought I had done more than enough research on this.
So when you say: "A 99-02 harness will not bolt in and function properly in a 03-07 classic truck. It will require repining to make it work properly."
are you talking about the "ENTIRE" harness motor and trans or just the trans harness?
and if I happen to find a 03-07 Van harness will it still require "RE-pinning" or will that harness plug n play?
AGAIN THANK YOU SO MUCH FOR YOUR HELP - I am trying to make this as easiest and quickest and painless as possible to get my truck back up and running.
Originally Posted by RedXray
As posted you'll need a 03+ harness. If you can't find one from an Express van to retain the cable throttle system you'll need an electronic accelerator pedal and TAC module (drive by wire). If the clips that hold down the MAP sensor are broken on the intake you can use the "cruise control bracket" (also holds down the engine cover part number 12561510) to hold down that sensor ($7 ebay)... pic below
Thanks RedXray!!! but I'm confused why would I need an electronic accelerator pedal and TAC Module? My Work truck is Drive by Cable and so is the engine, are you referring to if I have to get an 03+ Drive by Wire harness then I will need the electronic accelerator pedal and TAC Module?
when looking for an Express Van Harness (03 and up) I have noticed that their available for 4.8, 5.3 and 6.0 - That shouldn’t matter correct as long as it’s for DBC TB? But if I’m not mistaken the 6.0s were all DBW TB so stick with either the 4.8 or 5.3 - correct?????
Also I see that there are RWD and AWD vans does it matter if I get an AWD harness? Or do I have to stick with just the RWD version?
Now after all of this is said and done what computer will I have to use the OEM 05 V6 or the 99 V8 that came with the motor????? OR do I also have to source the computers from the Express Van???
I was just saying if you can't get a dbc van harness... you'll be converting to dbw.
Originally Posted by AngryRantLOL
I'm kinda pissed now because the whole reason for me looking for a DBC motor was because it was "Supposedly" Plug n play from one GMT truck to another and now this issue with the Harness. Nowhere and I mean nowhere was there a mention of the difference of the 99-02 harness to the 03-07 trucks.
I feel your pain. I was just the opposite my truck is a v6 2000... to a 2005 6.0 engine that came with DBW harness, throttle body and PCM. I emailed Brendon Patton from LT1 Swap and this was his reply:
Originally Posted by Brenden@LT1Swap
The 05 harness WILL NOT work without modification. It maybe far easier for you to get a factory 2000-02 red/blue V8 harness, and go with mechanical throttle. Its possible to make what you have work, but can’t even begin to explain pin for pin what needs done.
Basically the starter circuits are completely different (includes wiring for park neutral position switch), there are wires for cruise control that need moved around. Wire location for power circuits may need moved. Wouldn’t know without side by side comparison.
The Express vans with a 6.0 also were cable driven (I think) up to 05. Just make sure the van also has the 4L60E transmission. You will need a PCM (computer) that has the IAC (idle air control) chip on the printed circuit board (some DBW PCM's also have the IAC chip). If you grab the PCM from a 03+ van along with the wiring harness you should be gold. If you only have van the wiring harness you'll need to check the PCM you plan to use for the presence of the necessary IAC circuit.
On Brenden Patton's LT1 Swap web site he says in reference to IAC support PCM's... "Also, a tip on finding these. Any 4.3L V6 Pickup or S10-S10 Blazer/Jimmy will have the above computer, and can be programmed for the V8 Gen 3 LS engine." so your 05 v6 PCM may have the dbc chip, but the v6 PCM will need to be flashed with V8 parameters.
Read his page on DBC/DBW conversions. He has a list of PCM's and their service numbers that will work with DBC. The best way to tell is to remove the cover and identify if the PCM has the IAC stepper motor chip.
I was just saying if you can't get a dbc van harness... you'll be converting to dbw.
I feel your pain. I was just the opposite my truck is a v6 2000... to a 2005 6.0 engine that came with DBW harness, throttle body and PCM. I emailed Brendon Patton from LT1 Swap and this was his reply:
The Express vans with a 6.0 also were cable driven (I think) up to 05. Just make sure the van also has the 4L60E transmission. You will need a PCM (computer) that has the IAC (idle air control) chip on the printed circuit board (some DBW PCM's also have the IAC chip). If you grab the PCM from a 03+ van along with the wiring harness you should be gold. If you only have van the wiring harness you'll need to check the PCM you plan to use for the presence of the necessary IAC circuit.
On Brenden Patton's LT1 Swap web site he says in reference to IAC support PCM's... "Also, a tip on finding these. Any 4.3L V6 Pickup or S10-S10 Blazer/Jimmy will have the above computer, and can be programmed for the V8 Gen 3 LS engine." so your 05 v6 PCM may have the dbc chip, but the v6 PCM will need to be flashed with V8 parameters.
Read his page on DBC/DBW conversions. He has a list of PCM's and their service numbers that will work with DBC. The best way to tell is to remove the cover and identify if the PCM has the IAC stepper motor chip.
WOW!!!! Thanks again for that information!!! I was able to read through it and found out that the PCM that came with the motor has SERV.NO 09354896 sticker on the front but I did not get a chance to open it to confirm that the IAC chip is there. I will when I get a chance but at least that looks like one less issue that I will have to deal with, well besides having the PCM reprogrammed. and I sent an email to Brendan last night about that.
Do you happen to know if I can use either the RWD or AWD Express Vans Harness - does it matter if I get an AWD harness? Or do I have to stick with just the RWD version?
I guess if anyone has a lead on an 03 and up Express Van Harness please let me know.
WOW!!!! Thanks again for that information!!! I was able to read through it and found out that the PCM that came with the motor has SERV.NO 09354896 sticker on the front but I did not get a chance to open it to confirm that the IAC chip is there. I will when I get a chance but at least that looks like one less issue that I will have to deal with, well besides having the PCM reprogrammed. and I sent an email to Brendan last night about that.
Do you happen to know if I can use either the RWD or AWD Express Vans Harness - does it matter if I get an AWD harness? Or do I have to stick with just the RWD version?
I guess if anyone has a lead on an 03 and up Express Van Harness please let me know.
Thanks Again for the help
The issue you'll run in to with the 09354896 PCM is it has a Red/Blue connector and the 03+ harness you are looking for will have the Green/Blue connector. The o2 sensors are wired different between the two. The link above has info on how to swap pins around to make it work at the bottom of the page. That 4896 PCM is already programed for that engine so reprogramming shouldn't be necessary.
If the v6 05 (green/blue) PCM has IAC you can use that with no pin modifications but you'll need it flashed to run the V8.
Easiest option 03+ van harness with PCM
The other option will be using an 03+ Silverado, Sierra, Tahoe, Yukon, Escalade (4L60E) harness, PCM (your 05 PCM will work with flash) electronic throttle body, returnless fuel rail (drivers side) and a DBW pedal & TAC module. Check out your local pull-a-part, you may find a deal on either option above.
I'm pretty sure you'll need the returnless fuel rail anyway if your v6 05 only has one (supply) fuel line. The 99 LM7 you have should have two fuel lines a supply and a return.
The intake on the left (99-02) has the supply and return lines whereas the intake on the right (03+) has only the supply line. I have two because like I said above "I feel your pain"
The returnless rail dose NOT have the fuel pressure regulator on the rail as the 03+ fuel pump dose the regulating. (your 99 LM7 should have the vacuum diaphragm fuel pressure regulator on the rail... like the one on the left)
I believe the V6 all retained the fuel return line but hopefully he can confirm.
If it were me, I would use the V6 computer and have it flashed by someone competent. You would likely need to use an 03 operating system because of the return Fuel pressure regulator. Then get any 03-07 classic V8 harness and rewire the throttle body connection for the a manual throttle body. You can likely take them straight from the V6 harness too...
If you know which wire colors correspond to which pins in the DBW Throttle body you can extract them and switch them to the Drive by cable connections. Or you could take the whole harness apart and get the complete wires from the 99-02 harness and put them in the correct spot using an express van Pinout from 03-up
Van harness are longer at the PCM connection they also seem hard to come by. Most idiots in the JY cut them up when stealing parts off the motor in the self help yards.
04-15-2018, 12:34 AM
4.3 to 5.3 Wiring issues
