On-Board Diagnostics

ON-BOARD DIAGNOSTICS
The ACD-ECU monitors its input/output signals (some signals all the time and others under specified conditions). When an irregular signal is initially monitored, the ACD-ECU decides that a malfunction has occurred and records the occurrence as a diagnostic trouble code. There are 29 diagnostic items. The diagnostic results can be read with a scan tool. Diagnostic trouble codes are kept in memory by direct battery feed. The codes are retained in memory even if the ignition switch is in the LOCK (OFF) position.

Diagnostic trouble codes will, however, be erased when a battery terminal or the ACD-ECU connector is disconnected. In addition, the diagnostic trouble code can also be erased by scan tool MB991958 (M.U.T.-III sub assembly).

NOTE: If a sensor is disconnected when the ignition switch is in the ON position a diagnostic trouble code is stored in memory. In this case, erase the DTC using scan tool MB991958 (M.U.T.-III sub assembly).

The 29 diagnostic items are displayed in numeric order.