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 DTC. Depending on the failure, a DTC is stored in the first or second drive cycle. When a DTC is stored, the PCM turns on the malfunction 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 Temporary DTC and a DTC at the same time for the failure and turns on 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. The MIL does not come on. If the failure continues in the second drive cycle, the PCM stores a DTC and turns on 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 that allows the engine to continue running. A DTC is stored, and the MIL comes 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 for 15 to 20 seconds to check the bulb condition. If any readiness codes are not set to complete, the MIL flashes five times. If all readiness codes are set to complete, the MIL goes out.

Self Shut Down (SSD) Mode
After the ignition switch is turned OFF, the PCM stays on (Up to 15 minutes) to monitor 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 turning the ignition switch OFF.