4.3 to 5.3 problems
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Teching In
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4.3 to 5.3 problems I recently put a 5.3 out of a 04 Escalade into my 01 silverado single cab everything is on good and I have the harness and ecm from that motor the only problem I’m having now is there is a connector from the engine harness that’s white that’s not matching up with the truck body harness that’s blue I removed the pins from the blue connector and connected them to the white plug from the engine harness but the dash doesn’t light up anyways or does anything until I connect into the obd with a scanner the dash comes on but I remove the scanner it goes all off again I am at a loss here if anyone can help
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Joined: Mar 2005
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From: South Carolina
The 99-02 truck/suv harnesses are different than the 03+ truck/suv harnesses. The easiest way is to find a 99-02 engine harness, ECM and a cable throttle body. The 2004 ECM will work if it has the IAC chip soldered on the printed circuit board... some do some do not.
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
Originally Posted by Brendon@LS1Swap
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.
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.
Thread Starter
Teching In
Joined: Jun 2021
Posts: 9
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The 99-02 truck/suv harnesses are different than the 03+ truck/suv harnesses. The easiest way is to find a 99-02 engine harness, ECM and a cable throttle body. The 2004 ECM will work if it has the IAC chip soldered on the printed circuit board... some do some do not.
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
TECH Enthusiast
Joined: Mar 2005
Posts: 663
Likes: 384
From: South Carolina
Okay okay here’s my question now I also used the same transmission that came with that 5.3 and it’s a one plug on the transmission not like the one my truck had which was 2 where they glued them how would I go about that problem ? Do I have to change the whole transmission ? And I still have the v6 ecm as well would that one work if the v8 one doesn't have that chip ?
Standard NS85T PRNDL switch.
Thread Starter
Teching In
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Thread Starter
Teching In
Joined: Jun 2021
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You're probably referring to the PRNDL switch. On the trucks GM glues the harness connectors to the PRNDL switch and the switch usually breaks when trying to unplug the harness. The best way is to un-bolt the switch from the transmission and let it stay with the V8 harness if possible. I had to replace the switch (Standard Motor NS85T) on mine because of the glued connectors. The V6 ECM will work if it isn't the "black box" ECM which my 2000 had. I bought a P01 (0411) ECM for my swap.
Standard NS85T PRNDL switch.
Standard NS85T PRNDL switch.
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Thread Starter
Teching In
Joined: Jun 2021
Posts: 9
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The 99-02 truck/suv harnesses are different than the 03+ truck/suv harnesses. The easiest way is to find a 99-02 engine harness, ECM and a cable throttle body. The 2004 ECM will work if it has the IAC chip soldered on the printed circuit board... some do some do not.
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
I had the exact same issues swapping a LQ9 engine from a 2005 Escalade into my 2000 GMC Sierra. I emailed Brendon over at LT1Swap and asked if I could use the later 2005 harness in my 2000 Sierra.
Here was his reply:
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Verdad Gallardo TECH Enthusiast
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From: South Carolina
Thread Starter
Teching In
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hey guys back with a update still have a little problem now I got the truck to turn over and everything now with the harness but it’s shooting flames out the header when I’m trying to start it I’m lost here now i got the ecm that was with that harness which was out of a 2002 chevy tahoe do you I need to reprogram it maybe ? Or something else I’m pretty sure its on time when I had it done the dots lined up perfectly any help guys ? Also heard it could be the rockers if they’re too tight but I’m not too sure
Last edited by Rico214; Jun 25, 2021 at 06:38 PM.
