On-Board Diagnostics

LED Oxygen Monitor Lamp:

Diagnostic Connector Location:

Component Locations Schematic:

PURPOSE
The self-diagnosis system detects, stores and has provision for reading codes indicating various faults with electronic engine and emission controls. A "CHECK ENGINE" light on the instrument panel indicates the presence of trouble codes and flashes the codes. The system has a fail-safe function which will default to a preset value when a part is judged defective, thereby maintaining minimal driveability until repairs can be made.

LOCATION AND ID
^ CHECK ENGINE LAMP
On the instrument cluster.

^ O2 MONITOR LAMP
On the ECU (under the rear parcel shelf).

^ TEST MODE CONNECTORS (D-check)
Near the ECU (Green connectors.)

^ READ MEMORY CONNECTORS
Near the ECU (Black connectors.)

^ ELECTRONIC CONTROL UNIT (ECU)
Under the rear parcel shelf.

OPERATION
For accessing codes, two sets of connectors (Read Memory and Test Mode) and 2 lamps ("CHECK ENGINE" light and Oxygen Monitor) are used. The Oxygen Monitor lamp (it is an LED on the control unit) flashes the trouble codes. The connectors are for mode selection and the lamps monitor the type of problem.

The self-diagnosis system has four modes:

^ U-Check Mode:
Only components necessary for proper starting and drive operation are monitored. The "CHECK ENGINE" light will come on when a fault is detected, indicating the need for further diagnosis. Parts which do not significantly affect starting or driveability are not monitored in this mode.

^ Read Memory Mode:
This mode is used to read codes of past problems stored in memory and can be accessed when the "CHECK ENGINE" light is off. It is effective for detecting poor contact or loose electrical connections.

^ D-Check Mode:
This mode checks the entire system and displays any trouble codes currently being monitored.

^ Clear Memory Mode:
This mode removes trouble codes from memory after repairs are made.

Selecting Diagnostic Modes:

RELATIONSHIP BETWEEN MODES AND CONNECTORS

^ U-CHECK MODE:
Ignition "ON," Read Memory disconnected, Test Mode disconnected.

^ READ MEMORY MODE:
Ignition "ON," Read Memory connected, Test Mode disconnected.

^ D-CHECK MODE:
(engine on)
Ignition "ON," Read Memory disconnected, Test Mode connected.

^ CLEAR MEMORY MODE:
(engine on)
Ignition "ON" (engine on), Read Memory connected, Test Mode connected.