Differences and Applications of GM ECMs (GEN III, IV, & V)

Differences and Applications of GM ECMs (GEN III, IV, & V)



Everybody loves the GM LS Platform; but as much as we hate to say it, the LS is dead… and in its place lives the LT Platform.  Odds are you already knew this, but I’m betting you don’t know as much about the ECMs that powered these legendary engines; from the original LS1 powering the 1997 C5 Corvette to the modern day Z06, they’re all great engines, but nothing without a great ECM to control them.

The challenge every good tuner has - and one we constantly work to overcome when teaching our students how to tune, is the variety of changes that these ECMs have experienced over the years.  Because of this, we group these ECMs into three primary generations, the GEN III, IV and V. This article will focus on helping you understand the differences, strengths and weaknesses of these computers, so if you want to get better educated on these computers, read on!


One of the primary differences between the GM GEN 3 and 4 ECMs are how they estimate airflow using VE Tables.  A ‘VE Table’ is one of two methods used to control fuel delivery, typically the secondary method with the primary being a MAF (Mass Airflow Sensor). It models the airflow for the computer to calculate fuel.

  • The GEN 3 VE Table was a traditional table based on RPM and MAP.  Below is an example of a GEN 3 VE Table. The VE values in the table represent a ratio of how full (of air) the cylinders are, compared to their theoretical maximum.  The computer uses this information to calculate the correct amount of fuel required.

GEN 3 VE Table

  • The GM GEN 4 VE Table moved to Virtual (VVE) table instead, which uses a series of coefficients to predict VVE.  This really means that the computer takes real inputs like RPM and MAP, but then based on other inputs such as camshaft position and manifold runner position, it calculates a value.  This is a much more robust system which was required when the engines evolved to include features such as variable camshaft controls. Below is an example of a GEN 4 VVE Table, represented using air in grams/sec/sec, temperature corrected to Kelvin, as well as multiple camshaft angles.  The changes made are using the HP Tuners Virtual Volumetric Efficiency Table Editor, which makes your job much easier by graphically displaying the table as you see it - instead of as coefficients, which are much harder to work with for the typical tuner.

GEN 4 VVE Table

GEN III Applications and Features

The GEN 3 ECMs controlled many GM LS Engines from 1997 until approximately 2006 (model depending).  It controlled LS1, LS6, LS2 engines and more; and it was used in a variety of trucks, SUVs and cars as well.  The first in the line was the P01, which was used through about 2003, with the best models denoted as an 0411, usually pronounced, oh-four-eleven. This specifically references the P01 computers from 2001 to 2003. These modules are the more desirable versions of the preceding P01 due to a processor upgrade performed by GM. The 0411s are also much more robust than their "fragile" 1997-2000 predecessors which are easy to damage while writing tune files to them, rendering them permanently damaged.

One joke that’s prevalent among experienced tuners is that “if you are going to tune a '97 or '98, then you better have a pile of spare computers sitting on the workbench.” For these reasons, we recommend upgrading to a 0411 if you are going to be adding performance modifications to a '97 to '00 LS powered vehicle. It will require the re-pinning of a few wires in the harness, but that is something done with relative ease.  

The next GEN 3 module to be released was the P59 control module. These modules first originated in trucks and SUVs, but you will also find them in 2003 to 2005 Corvettes, as well as 2004 GTOs. While P59 computers closely mirror their P01 cousins, something interesting to note is that they are one of GM's first Flex Fuel capable ECMs. Flex Fuel gives the computer the ability to determine the Ethanol content in the fuel via a sensor placed in the fuel line supplying the engine. The computer can then seamlessly change the fuel output and spark advance on the fly to instantly compensate for a change in Ethanol content. This attribute is desirable to performance enthusiasts with the increasing popularity of E85 as a race fuel alternative.

The last hoorah for the GEN 3 computers is the E40 control module. E40s are strictly found in 2005 and 2006 LS powered cars. This makes the Pontiac GTO one of the most prime examples for this computer. With this module came a glimpse of the future and what was to come from GM as they headed towards GEN 4 computers. The E40s are essentially a hybrid, a testing ground for GM to start experimenting with features and controls that would eventually become the GEN 4 computer.

However, this also makes it the “red-headed stepchild” of GM ECMs, as it is known amongst tuners. There are several weird and quirky things that GM was trying out in this computer that only lasted a few years.

For example, the Mass Airflow Table was split in half. The MAF defines how much airflow is drawn into the engine by measuring the electrical resistance needed to keep a wire a specific temperature inside the air intake; this is called MAF Hertz. The computer knows that at a given Hertz value, a specific amount of air is being drawn into the engine. Based on that number, the computer knows how long to open the fuel injectors to achieve the desired air/ fuel ratio. In the P01 computers, the MAF table typically reads from 1,500 to 12,000 Hertz. The E40, on the other hand, splits the table into two with the first table reading from 1,000 to 5,800 Hertz while the second table reads from 5,800 to 12,200 Hertz. 

Another example is the dreaded Injector Flow Rate Limit. The injector flow rate table defines how much the injectors flow. With that information, the computer knows how long to open the injector to get a desired amount of fuel out of it. Upgrading fuel injectors to something with a higher flow rate is a must in most performance applications. The Injector Flow Rate Tables of the previous ECMs (P01 and P59) have a flow rate limit of 254 pounds per hour. This is more than enough for almost every application. However, when the E40 was released, it introduced a flow rate table that has a limit of 64 pounds per hour.  It is not hard to exceed this limit when installing aftermarket injectors for larger horsepower applications and requires some unique tune changes in order to get them to work properly. This 64-pound-an-hour limit hung around for quite a few years until being raised to 127 pounds per hour in roughly 2010.

GEN IV Applications and Features

2006 to 2007 brings us into the era GEN 4 ECMs, dominated by the E38. These computers were not phased out until 2016. In the early years of this computer, they did control a few LS2 engines, but they are primarily used for LS3s, LSAs, LS9s, and V8 truck and SUV engines. E38 computers were the most common among naturally aspirated factory engines, but forced induction factory engines (LSA, for example) were equipped with the E67 typically, a cousin to the E38.

The early E38s mirrored some of the bad habits from their E40 GEN 3 predecessor, but by 2010 the idle, fuel and spark controls were some of the best GM had created to date. This makes it one of the easiest ECMs to learn.  Because of their widespread use for so many years, odds are you will spend much of the time working with E38s. When tuning the E38, we typically find the Virtual VE system we discussed earlier in this article as the scariest part to handle; but any of our GM courses can teach you how to handle it easily.

The E67 computer was introduced In 2009 with supercharged 6.2 liter LSA in Cadillac CTS-Vs and LS9s powering the Corvette ZR1s.  This is the ECM of choice that GM used on all of their supercharged cars until switching to the GEN 5 ECMs with the LT4 in the 2017 model year. The E67 is nearly identical to its E38 companion with the exception of the utilization of two supercharger tabs in the software, one located under ‘Engine and Airflow’, the other located under ‘Engine and Torque Management’. While the E38 has these tabs and settings, they are not used in its applications.  See the illustration below for an example of the supercharger controls in the E67.

Supercharger Controls in the E67


Starting in 2011, we begin to see a new module come onto the scene called an E78. The applications for this computer are not widespread, with the primary application being the gas powered 2500 Silverados which utilize the E78 to control an LS2 based 6.0 liter. In fact, to the 2019 model year, if you buy a gas powered 2500 truck, it still comes equipped with the port injection 6.0 liter, making it the last remaining non-direct injected V8 engine in GM's current line up. Even with its limited applications, the E78 had significant implications for what was to come. This computer was the testbed for GM to start experimenting with the controls they would implement in the GEN 5 control modules paired with the direct injection V8 lineup. Just like the E40 was the hybrid test bed for the coming GEN 4 computers, the E78 seems to be the test bed for the GEN 5s.

What sets the E78s apart from their GEN 4 counterparts is the Torque management controls. If you are familiar with a typical GEN 4 computer and how its Torque management functions, you will quickly notice stark differences in the E78. The critical thing to note is that in the Torque management section, you cannot simply “max out” the settings, because this computer is Torque-based - like the GEN 5 computers of the next generation; which we will discuss more in the next section, covering the GEN 5 computers.


The primary difference between the GM GEN 4 and GEN 5 ECMs is Torque management.

Again, before we dive too far into the applications of the GEN 5 computers, let's define how to identify the differences of a GEN 4 and GEN 5 computer. While fueling and spark control are the same for GEN 5s as they are for GEN 4s, the real difference comes in the form of calculating how much Torque it should be making and then what the computer does about that calculation. Both GEN 4s and GEN 5s utilize a system called 'Virtual Torque.'

Virtual Torque is a system that calculates how much Torque the engine is making at a given operating condition. The calculation is heavily based on the amount of spark advance air in the cylinders, as well as camshaft position and more. This is important because there is no direct sensor on the vehicle that has the ability to measure how much Torque the engine is producing. Therefore, GM had to come up with a way to calculate it.

Just like the before mentioned Virtual VE Table, HP Tuners created a Virtual Torque Editor that gives you a physical table to modify in order to change data in the system in the background.

The Virtual Torque system enables the computer to achieve a target, not just limit the power output (like the GEN 4 ECMs did).  For example, if the Maximum Torque Limit 1st gear Table says that at 2,000 RPM the engine cannot exceed 243 foot-pounds of Torque, but the computer calculates that the engine is making more Torque than that, the computer will take measures to bring the Torque down to the 243 foot-pound limit.

The true difference comes in with Driver Demand Tables. These tables are designed to act as a target for what the engine should be making for Torque. Therefore, the GEN 5 computer knows how much Torque it is making, how much Torque the limit is, and with driver demand tables how much Torque it should be targeting. By looking at the Driver Demand Tables, the ECM can map the amount of Torque at a given RPM or Vehicle Speed. So where Virtual Torque represents how much Torque the computer thinks the engine is producing, the Driver Demand Tables represent how much Torque the computer wants to achieve.

Everything is taken one step further and based on what Torque Driver Demand wants; the computer will manipulate the throttle body angle, spark advance, and sometimes fuel delivery to get the engine Torque to meet its target. This can be a problem when you have modified the engine to make more Horsepower and Torque because the system is going to continually try and fight you to bring the engines Torque output back down to a stock level. For this reason, GEN 5 control modules need specialized attention when it comes to tuning them, which we address in our GEN 5 courses.

GEN V Applications and Features

Knowing when GM started using GEN 5 computers is simple - if it is a direct-injected V8 engine, then it uses a GEN 5 control module. So, if the car or truck you are looking to tune has an LT1 or LT4 engine, then you are dealing with a GEN 5 computer. This means Corvettes, Camaros, trucks, and SUVs from 2016 and newer all have GEN 5 computers. If the GEN 5 computer you are dealing with is older than 2017, then it is an E92. If it is 2017 or newer, then it is an E92A.

As the OE Manufacturers continue to push the envelope on engine performance and technology, the world of ECMs is going to keep evolving. One thing is certain though, our team here at The Tuning School will be here leading the charge in teaching you what you need to know to be a successful tuner with the latest and greatest in ECM logic and technologies. 


If you'd like to dive deeper and learn first hand how to tune these applications, check out our collection of GM based courses for HP Tuners and Holley EFI.
Have questions about where to get started? Contact the team and we'll be happy to assist you!

Previous post Next post