Engine and transmission swap

WESTERNREACH

MEMBER
1999 GMC SONOMA
4.3L
V6
2WD
AUTOMATIC
150,000 MILES

Hi, would a 2002 GMC Sonoma 2wd extended cab pickup 4.3. Liter engine and transmission fit into a 1999 GMC Sonoma 2wd regular cab pickup 4.3 liter?
I know the 1999 has an EGR Valve, whereas the 2002 doesn't.
What would I have to swap out? PCM? Wiring harness?
Thank you

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

Yes, you will have to swap out the harness and all the sensors including the PCM. If you do not and the EGR connection has nowhere to go, then you will have many codes set for the system since it is missing.

Roy

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Monday, February 4th, 2019 AT 3:51 AM

WESTERNREACH

MEMBER
22 POSTS

Hi Roy, thanks for the reply. Do you happen to know if the harness would have to be cut and spliced, or is it something to just unplug and plug in? In other words would it be just the harness in the engine compartment or would it be all the harness into the passenger cabin including the fuse box?
I would (theoretically) have the whole donor vehicle (2002 GMC) at my disposal, so when swapping the motor and transmission would it be safe to assume, I can unplug the engine harness, PCM and just re-plug it into the 1999 GMC?
Thank you,
Steven

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Monday, February 4th, 2019 AT 11:17 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

You will need the harness into the passenger compartment. The complete harness.

Roy

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Monday, February 4th, 2019 AT 12:58 PM

WESTERNREACH

MEMBER
22 POSTS

Hi Roy,
One more question for further clarification. Will the "complete harness" be just up to/behind the fuse box itself?

Not the harness under the dash throughout the passsenger cabin, (interior lights, speedometer, radio, etc. Etc.)? I would imagine that part of the harness can remain? Thank you, Steven.

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Monday, February 4th, 2019 AT 7:29 PM

ASEMASTER6371