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Project 1999 truck with 7.4L and 4L80E PCM swap.
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Post Project 1999 truck with 7.4L and 4L80E PCM swap. 
Hello, My name is Jonas and I live in Sweden.

I am new to this forum and I registred because there seems to be a lot of knowledge on this site.

I am starting on a new project now with some special requirements and I have a plan on how to do it.
We need a vehicle with a lot of pulling force, and we need to control the acceleration and final pulling speed within tight limits. ( less than 1 Mph )

We bought a 4WD 1999 K3500 truck with the 7.4L Vortech and a 4L80E transmission.
I thing the PCM is a 16263494 blackbox with four connectors.

I think that this is a good truck with strong axles and if needed it is possible to increase engine power quite a lot using boost.

The idea is to replace the stock PCM with an aftermarket unit that has a lot more inputs, outputs and prorgamming options.
To be more specific this one: http://www.maxxtuning.eu/products/engine-control-and-electronics/maxxecu-standalone-ecu/maxxecu-pro-flying-lead-competition-kit
I will use an external high resolution speed sensor and l with program the desired acceleration curve into a speed limit function in the MaxxECU.
The driver will just steer and floor it.

I would like to get an extra PCM and use the connectors from that to build an adapter harness. That way it is possible to reinstall the stock PCM in the future, and I don't have to destroy the engine/transmission harness.
I will problably save a lot of time too.

Question 1: What are my options on the PCM to use connectors from. What years and vehicles use the same connectors?

Question 2: Where can I find the PCM pinout and scematics for this 1999 7.4L truck?

Thanks!

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I now have the ECM pinout thanks to Lextech.

Found some schematics.

http://www.fullsizechevy.com/forum/showthread.php?213662-96-99-454-Vortec-owners/page466

1999 L29

http://s1106.photobucket.com/user/PCMCalibrator/library/Schematics/1999%20454/L29




1999 L21 - Same engine with coil on plug and electronic throttle body.

http://s1106.photobucket.com/user/PCMCalibrator/library/Schematics/1999%20454/L21







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Another possibility might be to pick up a complete engine harness to modify. It's fairly easy to change the whole thing - the fuse box unbolts from the inner fender, there's a connector that goes through the firewall down low below the brake booster, and there is a bulkhead bolted to the passenger side firewall that goes through to the HVAC.
The differences between models I can think of off the top of my head: pickup models have an extra relay for lighting, some have a relay for a smog/A.I.R. pump clutch if equipped, some have two extra circuits for heated seats if equipped, and Suburban harnesses have an extra wire for rear HVAC.
I'm sure used Chevy parts aren't nearly as accessible for you there as they are here but these trucks do turn up on-line being parted out.

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The smaller S10 trucks use the same PCM part number and I found one on a junkyard for $100.

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