Glossary
ECU / ECM: Electronic Control Unit / Engine Control Module
The controller that runs a system; ECM usually refers to the engine controller specifically.
Definition updated 2026-10-25 · Report a correction
What the terms mean
ECU stands for Electronic Control Unit. It is a general term for a controller that runs a system, reads inputs, and commands outputs. ECM stands for Engine Control Module and usually refers to the engine controller specifically. Some manuals use the terms interchangeably; others use ECU for a body or chassis controller and ECM for the engine.
A powersports machine can have several controllers: engine, electric power steering, ABS, display, telematics, and a transmission or drive-mode module. Each can publish its own diagnostic table. The same code number in two modules can mean two different things, so the module is part of the code identity.
Multiple controllers on one machine
The archive preserves the source chapter for each table. A Segway UT10 page, for example, can come from an ECU chapter, an EPS chapter, a T-BOX chapter, or an ABS chapter. Arctic Cat publishes a shared EPS table, and Polaris publishes module-specific tables such as the E-VES exhaust-valve controller. Those tables are not interchangeable even when the code format looks similar.
The model page source box names the chapter and links to the OEM file. That is the fastest way to see which controller a row belongs to. The code index also records the page where a key appears, but the module context is on the page itself.
Why the module matters in a lookup
A code lookup that ignores the module can land on the wrong label. A P-code in an engine table and a P-code in a chassis table can share the same letters and digits without sharing a meaning. The archive therefore keeps the model year, the source, and the printed label together instead of publishing a single global code dictionary.
When the module is known, start with the model page and read the source box. When only the code is known, use the decoder or the code index, then confirm the module on the linked page.
Reading a module-specific table
Module tables often have extra columns. A fault-setting column describes when the controller sets the code; a fault-healing column describes when it clears it. Some module tables print a short description and a longer description. The archive preserves those columns when the source publishes them, because the wording can differ from the main engine table.
The EPS entry is an example of a module-specific vocabulary. The DTC entry explains why the archive counts rows rather than unique code numbers.