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)

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Description of On-Board Diagnostics

The Engine Control Module (ECM) monitors the input/output signals (some signals at all times and the others under specified conditions). When the ECM detects that an irregularity, it memorize the diagnostic trouble code, and outputs the signal to the self-diagnosis output terminal. The diagnosis results can be read out with Malfunction Indicator Lamp (MIL) or Scan Tool (ST). The Diagnostic Trouble Code (DTC) will remain in the ECM as long as battery power is maintained. The DTC will, however, be erased when the battery terminal or the ECM connector is disconnected.

NOTE: If the sensor connector is disconnected with the ignition switch turned on, the DTC is memorized. In this case, disconnect the battery negative terminal (-) for 15 seconds or more, and the diagnosis memory will be erased.