PCM tuning refers to the software and calibration modifications I've made to the truck's Powertrain Control Module, which is the computer that controls the engine. The LQ9 control system is very complex and is repsonsible for controlling fuel delivery, spark, transmission shifting, error diagnostics, and a multitude of other powertrain functions. The PCM is located underhood and is modified by connectiong a PC with appropriate tuning software to the OBD-II diagnostic connector under the dashboard with a special link cable. The software I use for tuning is called EFI Live FlashScan, and is an excellent product. Lean more about it here.
The first steps to get my 2002 engine operating correctly in my 1995 truck were pretty simple. I had to disable support for the systems that were no longer present on the engine, such as the EGR system, body control system, catalyst monitoring system, etc. Next I removed some power limiters such as the engine torque reduction feature that's designed to prevent explosion of the wimpy 4L65e transmission that is usually installed behind an LQ9 engine. I also had to upgrade to a PCM operating system that supported the 4L80e transmission. Finally, I set up the auxiluary systems such as the calibration for the speedometer based on my tire size and gear ratios, diagnostic options, etc.
The next step for tuning is still in progress. Since the airflow characteristics of the engine have been changed with a different air intake system, exhaust system, and camshaft profile, the Volumetric Efficiency table in the PCM needed to be remapped. This was done by using an EFILive exclusive feature that generates a table of correction factors for the VE table using a wideband oxygen sensor. A wideband oxygen sensor is a device that can determine the precise air-to-fuel ratio of the engine by analyzing the exhaust gas composition. I purchased an Innovate LC-1 WBO2 sensor and attached it to my FlashScan interface cable to complete this tuning step.
Future projects include more tuning to optimize power output, and the addition of one interesting device. This device will be a module that attaches to the PCM communication bus and will display pertinent engine information such as spark timing, cooling fan status, and transmission temperature on an LCD mounted in the dashboard. This will be a device designed by myself for my specific application.
Pictures and screenshots to come.