Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Controller Area Network Data Link






Controller Area Network Data Link

The Engine Control Module (ECM) communicates with all data bus capable control modules by a CAN data link.

The data bus capable control modules (i.e. engine coolant temperature sensor) are connected by two data bus wires which are twisted together (CAN_High and CAN_Low), and which exchange information to the ECM. Missing information on the data bus is then recognized and stored as a malfunction.

The ECM illuminates the malfunction indicator lamp (MIL) through the CAN data link and tells the MIL to turn on, turn off, or flash.