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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 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 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 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.