I am doing a 3400 swap in my 97 cavy. I read that it would be easier if my car was an 00+. Well I am looking to do a dash conversion to an 03 sunfire. My question is if i replace the dash harness with a 00+ harness what BCM would I need and what ECU. The motor harness i have is from a 99 Grand Am. thanks

Not sure what year of GA harness you would want. If you were planning on running Megasquirt then you could run a stock PCM and just splice in the MS unit. Though it would cause a slight problem if you have a 4spd auto.





i find it amusing that SHOoff has nothing better to do but follow me around & be an unhelpful dick in even cross-forum. - Jon Mick

sorry forgot to mention I am running the 4T45e

You're going to want an 00+ ECM and harness, but the problem you're going to run into is that the flash that runs the gauges is for a 4T65e, not a 4T45e, and the shifting is off. It has been tried and the tranny doesn't shift properly. To my knowledge, no one has yet figured out the way to flash the data stream description from the Impala flash (which runs the gauges) onto another flash. The problem is that most tuning programs (I say most because I'm not 100% sure that none of them do) aren't set up to mess with the data stream, just the tuning parameters.

As for which BCM and dash harness, just get the one from whatever car the dash comes from. Any 00-05 should be the same.

can you and how hard will it be to swap in the 4T65e tranny? and what are the pro and cons between the 4T45e and 4T65e?

Talk to John Lenko. He used a 4T65e on his 3800. I'm not sure what the mounting differences are.
I do know that there are things you need to do with the axles to fit them. I don't think it's a terribly difficult project, but it isn't a simple bolt-in job.

I have the Heavy Duty version though (4T65E-HD), which is what comes with the L67. It's pretty big..

with me changing out to 00+ do i need to replace the HVAC, radio, blower, and fuel pump?

You will need to replace the fuel level sending unit in the tank, because the impedance range changed. I am not 100% sure on the radio, but the rest doesn't need to be changed.

Most people say don't do this, but if your have patience you could piggyback the ECM's. You wouldn't have to change the dash harness, the fuel sender, or the bcm. I did my wiring harness in one night, but I also have a few problems with the wiring I need to work out, just take your time and do the wiring over a few days, double and triple check everything, you should be ready to go.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

Besides the fuel sender the 00+ dash harness is an easy swap. You will keep you radio, hvac, blower harness in the car now. Everything else pretty much just plugs in. You will have to tie the engine wiring in on the other side of the firewall, but that is easy also if you have the diagrams for both cars. I am working on the same setup now. 95 Z with 00+ dash harness and 99 alero ecm.

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Edited 1 time(s). Last edited Tuesday, September 15, 2009 8:39 PM

I have also been hearing bout a 3 wire coolant temp sensor. Where do I find one of those?

Your engine should already have one. It is right under the throttle body. It's a triangular weather pack plug, and the wire runs back under the upper intake manifold. The wires should be green, yellow, and black.

Edit:I just thought as I hit post: the wires may possibly be orange, yellow, and black. Not sure why the difference, but I've seen it in both combinations.




Edited 2 time(s). Last edited Friday, September 18, 2009 5:47 AM

JAS wrote:I have also been hearing bout a 3 wire coolant temp sensor. Where do I find one of those?

Not all 3400's have them. If not you order a CTS for a 93 Cavalier with a 2.2L engine. You can also use a plug for a TPS on it. That's what I did.





i find it amusing that SHOoff has nothing better to do but follow me around & be an unhelpful dick in even cross-forum. - Jon Mick