Description of On-Board Diagnostics

Electronic Control System

The functions of the fuel and emission control Systems are managed by the powertrain control module (PCM) on vehicles with automatic transmissions.

Self-diagnosis
The PCM detects a failure of a signal from a sensor or from another control unit and stores a temporary DTC or a permanent DTC in the erasable memory (RAM). Depending on the failure, permanent DTC is stored whether in the first or the second drive cycle. When a permanent DTC is stored, the PCM indicates the m2lfunction indicator lamp (MIL) by supplying ground to the MIL circuit.

- One Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor or from another control unit, the PCM stores a permanent DTC for the failure in the RAM and indicates the MIL immediately.

- Two Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor or from another control unit in the first drive cycle, the PCM stores a temporary DTC for the failure in the RAM. The MIL does not come on at this time. If the failure continues in the second drive cycle, the PCM stores a permanent DTC in the erasable memory and indicates the MIL.

Fail-safe Function
When an abnormality occurs in the signal from a sensor or from another control unit, the PCM ignores that signal and assumes a pre-programmed value for them and allows the engine to continue running. DTC is stored at this time and MIL come on.

MIL Bulb Check and Readiness Code Condition
When the ignition switch is first turned ON (II), the PCM supplies ground to the MIL circuit and indicate it for about 15 to 20 seconds to check the bulb condition. If any readiness codes are not set to complete, the MIL flashes five times during this time. If all readiness codes are set to complete, the MIL will go out.

Self Shut Down (SSD) Mode
After the ignition switch is turned OFF, the PCM stays on (up to 15 minutes) to keep watching the condition of the vehicle. If the PCM connector is disconnected during this time, the PCM may be damaged. To cancel this mode, disconnect the negative cable from the battery or jump the SCS line with the HDS after the ignition switch is turned OFF.