I've been working on this swap for almost 2 years, and just when I'm practically done, I come across a real head-scratcher.

I'm swapping in a 98 A/T 4Runner 3.4 engine into my 93 A/T 4Runner using the stock transmission, complete custom harness (thanks Mike!), and a 98 T100 ECU to run the tranny. Everything has bolted on perfectly. The truck starts and runs. With the original MAF, the CEL came on with code P0113, which means the Temperature Sensor in the MAF is reading too low (it was giving a -40ºF reading IN THE CARIBBEAN). So, problem easy to solve, right? I bought another MAF, same part number, same version (it's the big bulky one), and guess what? CEL came on with code P0100: MAF Circuit Malfunction.

Obviously, my rage letter to the people who sold me the MAF didn't waited more than 1 hour. However, during that hour, the mechanic who's helping me with the swap tried out another MAF from another 4Runner with NO CEL he had in the shop from a client, and guess what again? He got the same CEL code: P0100.

Something's not quite right here. First, I get one code, then a get a different one, and then the same one for 3 different MAFs. We tried out all the instructions from the Factory Service Manuals that checked the wiring from the MAF to the ECU and everything checked out normal. We're still trying to troubleshoot what's causing this, but it's been 8 days and still nothing.

So, here I am.... any suggestions or ideas?

Also, I'm not running any of the O2 sensors (not plugged in). Not sure if this is a factor, but just in case.

 

your swap harness has a problem. If the COR isn't wired correctly it can throw that p0100

 

Yeah, you need to get on the phone with Mike. There's a simple mistake in your harness.

 

vasinvictor: I contacted ORS via email on Thursday and again last night. I havent receieved any answer yet (which is unusual), but maybe they're trying understand what could be causing the problem before replying me. *crosses fingers*

 

Forgive me for asking, but what does COR stands for? Spanish is our first language here (Puerto Rico), and even though Im pretty good with English, most technicallities are not taught in school!!

 

Circuit opening relay

 

Problem solved: Mike informed me that the conversion harness was accidentically designed to work with the newer model of the MAF. He suggested to exchange some wires at the MAF plug. I did, and the problem was perfectly solved.

 

Glad to hear.