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Vehicle Tuning and Remapping Glossary

When it comes to tuning/remapping an engine, people use a variety of terms for the same processes, parts, and protocols. To help you sort through the lingo, BenchForce created this user-friendly Glossary to cut through any perplexity.

Not seeing what you need? Drop us a line if there are other aspects of tuning/remapping that you’re interested in learning about. We’ll continue to add more terms as we build out this resource, so be sure to check back for updates.

What Are Accelerator Pedal Maps?

The accelerator pedal map is a part of the engine control unit (ECU) map that shows the pedal opening percentage and throttle butterfly valve angle. Essentially, it allows drivers to program how the engine "feels" by increasing or decreasing the amount of torque present when they push on the throttle.

What is a Body Control Module (BCM)?

The Body Control Module (BCM) controls the windows, radio, fan, air conditioning, instrument or gauge cluster, and various other components. It may also be referred to as the “body computer.” It does not monitor or control any engine functions; instead, it is solely focused on the vehicle’s accessories. A common symptom of a failing BCM is security function errors or the appearance of warning lights on the dashboard.

What is a Controller Area Network (CAN bus)?

A Controller Area Network (CAN bus) is a vehicle bus, which is a specialized internal communications network that interconnects components inside a vehicle, that allows electronic control units (ECUs) and devices to communicate with each other's applications without a host computer. Think of it as the central nervous system of a vehicle.

The CAN bus is a protocol that links all of the electronic subsystems, such as anti-lock braking, cruise control, and power windows, within a vehicle so they can communicate with each other. Bosch originally developed CAN to reduce cable wiring, so ECUs could communicate with a single pair of wires: CAN high (CANH) and CAN low (CANL).

What is a Diagnostic Scan Tool?

Also known as a scan tool, code reader, and OBD scanner, a diagnostic scan tool connects to an OBD port (which is usually found under the driver side dashboard) and reads diagnostic trouble codes (DTCs) to identify what is wrong with an engine.

Some diagnostic tools will give you both the code and a description of the issue. If you're using a cheaper scan tool, you may have to use a DTC troubleshooting index to identify the problem.

Many diagnostic scan tools can also give the user information on myriad other areas such as engine temperature, fuel rate, O2 sensor voltages, battery voltage level, and engine run time.

What are Diagnostic Trouble Codes (DTC)?

Diagnostic Trouble Codes (DTC) are stored in your vehicle's onboard diagnostic system and alert you to a vehicle's problems. Unlike the OBD-II system that is uniform across all vehicle makes and models, the codes can still vary from one manufacturer to the next. However, if you have an OBD-II scanner, you can connect it to the OBD-II port and read the DTCs from the computer.

The Society of Automotive Engineers (SAE) created DTCs to help with emission regulations and develop standards for automotive engineers. The codes are five characters long—they're made up of one letter and four numbers.

The letter alerts you to which general section of the vehicle the problem is in. The first number will let you know if the problem is standardized or manufacturer-specific. The second number tells you which subsystem has the issue. The fourth and fifth number pinpoints the particular issue with the vehicle.

What is an Engine Control Module (ECM)?

The engine control module (ECM) is the engine's computer that controls engine performance. It uses information from sensors to adjust different elements of your engine operation, such as the fuel injection or spark timing. If sensors send information to the ECM that indicates a problem, it will send a signal to the check engine light. Mechanics, car enthusiasts, and those interested in repairing their own cars can use an onboard diagnostic scanner to find the issue.

It's also what gets "tuned" or “remapped” when programming an engine. Depending on the manufacturer, the ECM may also be called a(n):

  • Engine control system (ECS)
  • Engine control unit (ECU)
  • Powertrain control module (PCM)
  • Vehicle control module (VCM)

Essentially, the ECM is the "brains" of an engine. Manufacturers set ECMs to standard settings. Modifying the ECM software is known as "remapping an engine."

What is an Engine Control Unit (ECU)?

*See What is an Engine Control Module (ECM)?*

What is the Engine Coolant Temperature (ECT)?

This sensor measures the temperature of the engine’s coolant temperature. It indicates (and often prevents) overheating, freezing, and engine corrosion. More specifically, the ECT gauges how much heat is currently being emitted from the engine. The typical range of the engine coolant temperature is from 195 to 220 degrees Fahrenheit, but these values depend on the make, model, and year of the vehicle. The ECT can be found on the dashboard of your vehicle near the gas gauge, and the temperature is represented by a needle that fluctuates between “H” for hot and “C” for cold.

What is the intake air temperature (IAT)?

The intake air temperature sensor measures the temperature of air that is being drawn into the engine through the intake manifold. The sensor then sends this information to the Engine Control Unit (ECU) so that it may balance the ratio of air to fuel.

To balance the ratio, the ECU changes the length of the voltage pulses. High temperatures require lower voltage pulses, while low temperatures require high voltage pulses. There may be an issue with the intake air temperature sensor if the check engine indicator lamp turns on, there are problems starting the vehicle, there is reduced engine power, or you notice increased fuel consumption.

What are LS Engines?

Since 1997, the LS engine is one of the most popular engines in history created by General Motors (GM). The benefits of LS engines over previous classic small-block V-8s include, but are not limited to:

  • Aftermarket support
  • Performance
  • Price
  • Size & weight
  • Strength of block

What is Manifold Absolute Pressure (MAP) Sensor?

MAP Sensors are located in fuel-injected vehicles. The manifold absolute pressure sensor sends information to the powertrain control module (PCM) about the air pressure within the intake manifold and the engine's current load.

The PCM uses the MAP sensor’s data to calculate fuel injection. When more air is sucked in as the engine starts, more fuel is required to keep the ratio balanced. In addition to monitoring the amount of fuel utilized, the MAP Sensor also helps determine ignition timing.

A MAP Sensor may fail when moisture enters the system. Failure may also occur due to normal wear over time and vibrations from driving the vehicle. If your check engine light has turned on, look out for these OBD-II codes that indicate a failing MAP Sensor or a failure associated with the sensor:

  • P0068
  • P0069
  • P0105
  • P0106
  • P0107
  • P0108
  • P0109
  • P1106
  • P1107

A MAP Sensor may also be called an Engine Load Sensor, Pressure Sensor, and Boost Sensor.

What is the Mass Air Flow Sensor (MAF)?

The Mass Air Flow Sensor measures the amount of air flowing into the engine. It is located between the air filter and the engine’s intake manifold. Once the amount of air flow is determined, that data is then passed on to the Engine Control Unit (ECU), which delivers fuel to the engine. If the mass air flow sensor is faulty or damaged, the engine may experience a number of performance issues, such as:

  • The engine is hard to start or turn over
  • The engine stalls shortly after starting
  • The engine hesitates or drags while under load or idle
  • Hesitation or jerking during acceleration
  • The engine hiccupping


What is OBD-II or OBD2?

OBD-II stands for onboard diagnostics II and is a set of standards and parameters in your vehicle's self-diagnostic system. OBD-II monitors emissions, mileage, pressure, speed, spark-plug misfires, and a variety of other data about your car. If the computer detects a problem with your vehicle, the "check engine" light will illuminate.

OBD-II features a 16-pin port located under the driver's side dashboard. Mechanics, automotive enthusiasts, and even regular people interested in getting a clearer picture of what is wrong with their vehicle can plug a diagnostic scanner tool into the OBD-II port to view the diagnostic trouble codes (DTCs).

The California Air Resource Management Board (CARB) created the OBD system in 1991 to reduce pollution. In 1996, The Society of Automotive Engineers (SAE) created the OBD-II system to standardize DTCs and the OBD connector across manufacturers.

There are five basic signal communication protocols (we've included the variants as well):

  1. SAE J1850 PWM: Pulse Width Modulation, used in Ford vehicles
  2. SAE J1850 VPW: Variable Pulse Width used in General Motors vehicles
  3. ISO 9141-2: Used in all Chrysler and a variety of European or Asian vehicles between 2000-2004. Uses pins 7 and 15
  4. ISO14230-4 (KWP2000): Keyword Protocol, used in a variety of European and Asian imports as well as Honda, Jeep, Land Rover, Subaru, Mazda, Nissan, and more. Most cars between 2003-2008 using a K-Line. Uses pin 7
  • ISO 14230-4 KWP (5 baud init,10.4 Kbaud)
  • ISO 14230-4 KWP (fast init,10.4 Kbaud)
  • ISO 15765 CAN//SAE J2480: Controller Area Network, used on all vehicles manufactured after 2008
  • ISO 15765-4 CAN (11 bit ID,500 Kbaud)
  • ISO 15765-4 CAN (29 bit ID,500 Kbaud)
  • ISO 15765-4 CAN (11 bit ID,250 Kbaud)
  • ISO 15765-4 CAN (29 bit ID,250 Kbaud)

What is Quad-Cam?

A Quad-Cam refers to an engine featuring a dual overhead camshaft and four valves per cylinder instead of two. It was developed by General Motors (GM) in the 1980s with the intention of giving vehicles more power and better performance. These camshafts ensure that exhaust is expelled while simultaneously allowing air inside the engine—two camshafts control the air intake valves while the other two control the exhaust valves. Each additional camshaft maximizes airflow.

What is the Throttle Position Sensor (TPS)?

The Throttle Position Sensor (TPS) measures the percentage of throttle input from the accelerator position sensor (APP), by regulating how far open the throttle valve is opened. More importantly, it assists in determining the combination of air and fuel that is guided to the engine. If the TPS is faulty and will not open to let air through to the engine, the car will not start.

What is a Transmission Control Module (TCM)?

A transmission control module controls the transmission in an automatic vehicle by receiving input from various sensors about an engine’s current load and then activates the torque converter control/clutch to let the vehicle switch to the optimal gear. The TCM can be located in the powertrain control module or be a standalone controller.

What is a Torque Converter Control/Clutch (TCC)?

The torque converter control is a system inside the engine control module (ECM). Using a solenoid-operated valve, the TCC reduces slippage losses and regulates fuel mileage and fluid temperatures.

What is the Vehicle Speed Sensor (VSS)?

The Vehicle Speed Sensor (VSS) measures the speed that the vehicle is in motion. Specifically, the sensor reads the speed at which the vehicle’s wheels are rotating. It is also part of your vehicle's anti-lock braking system (ABS).

The ECU uses the data the sensor collects to determine ignition timing, the air to fuel ratio, transmission shift points, and to initiate diagnostic routines. A defective VSS can negatively impact automatic transmission operation.