Gen III PCM control goes beyond the engine to be one of best solutions for electronically controlled 4-speed automatic transmissions. Owners not using the LS1 PCM for engine control must look to the aftermarket for a standalone transmission controller that may cost in excess of $1,000. While many who desire an automatic transmission choose either […]

Gen III PCMs are powerful control modules but they are of little use without tuning software to change engine (and transmission) operating parameters. Before getting too far into a discussion of electric fans and PCM calibrations, it is important to first consider air conditioning control.   This tech tip is from the full book, HOW […]

General Motors introduced electronic throttle, or drive-by-wire, with the LS1 engine in the 1997 Corvette. Electronic throttle was released before cable throttle for the LS-series engine family. In 1998, the Camaro and Firebird received a cable throttle LS1 engine. The GM trucks received LSseries engines in 1999 and, depending on make/model, were available with either […]

Let’s begin this chapter by agreeing that the “LS1 PCM” is just an ECU that has the designed purpose of controlling the sequencing of ignition and injector events based on a variety of sensor inputs. We can then agree that this ECU is uniquely programmed so that combustion results are favorable so that the stoichiometric […]

Production GM vehicles rely on the PCM to provide signal outputs to control the engine, gauges, electric fans, emissions equipment, air conditioning, and other equipment. Engine Control Output The basic purpose of any engine computer is to correctly deliver fuel and initiate ignition events for any engine operating condition. To do this correctly, engines are […]

Vehicles are equipped with a variety of sensors that are used by the PCMs to perform their intended functions. Since the introduction of GM electronic fuel injection, the sensors have changed in form, but not function. In most cases, early GM sensors are directly compatible with the Gen III PCMs. They all have significant importance […]

Although Gen III PCMs are powerful control modules, they are of little use without tuning software to change engine (and transmission) operating parameters. You may find that the best results involve a blend of tuning services at an experienced dyno facility and final do-it-yourself tweaking using a popular scan-and-tune software package. The aftermarket offers all […]

OBD-II compliance in 1996 brought a new ignition system to Vortec V-6 and Vortec V-8 engines. Engine position through a crankshaft sensor and reluctor wheel also meant improved ignition accuracy and misfire detection. Older HEI distributor ignition systems deliver spark and fuel based on distributor position. For these early systems, accuracy of spark and fuel […]

GM ECMs have come a long way since the introduction of the first multi-port injection V-8 ECM used in the 1985 TPI Camaro, Firebird, and Corvette. These early ECMs require a PROM (or “chip”) that contains the engine’s calibration data. While all TPI ECMs are for use with high energy ignition (HEI) systems, which requires […]

The identification of a GM engine is commonly referred to by its RPO code. A Regular Production Option (RPO) is made up of three lphanumeric characters to uniquely identify a vehicle option. In 1985, General Motors introduced the 5.7L multiport injection engine as RPO “L98.” However, while the RPO “LS1” is specific to the 5.7L […]