Key On Engine Running (KOER) Self Test Description

PURPOSE
The Key On Engine Running (KOER) test performs various Electronic Engine Control (EEC) functions and looks for expected engine response. The KOER test examines the fuel system, selected sensors, EGR system, idle speed control, knock detection system and dynamic system response during their normal operating conditions to determine if any problems or malfunctions exists.

OPERATION
The KOER self-test indicates that it has started by sending an engine identification code. It then tests inputs and EEC-IV controlled functions by forcing various conditions and looking for expected engine responses.

The KOER self-test conducts the following additional checks to determine if the Electronic Engine Controls (EEC) system is operating properly.

Dynamic Response Check
The dynamic response check is used to verify operation of the throttle position, mass air flow, manifold absolute pressure, and knock sensor during a brief wide open throttle condition (goose test).

Power Steering Pressure Switch (PSP) Test
After the ID code has been received the steering wheel must be turned one-half turn and released. This tests the ability of the EEC system to detect a change of state in the PSP input.

Brake On/Off Test
After the ID code has been received the brake pedal must be depressed and released. This tests the ability of the EEC system to detect a change of state in the brake on/off switch.

Transmission Control Switch (TCS) Test
After the ID code has been received the TCS switch must be cycled. This tests the ability of the EEC system to detect a change of state in the TCS.

Upon completion of the test any ON DEMAND (hard) codes that are identified will be output.

INITIATING
The KOER self-test may be initiated manually or with a scan tool. Refer to Key On Engine Running (KOER) Self Test. Key ON Engine Running (KOER) Self-Test


IMPORTANT NOTES
- Vehicle should be at normal operating temperature prior to commencing the test.

- Turn engine "OFF" and wait 10 seconds prior to initiating the test.

- The KOER self-test only displays codes which are present at the time of testing (hard, on-demand codes). This test does not display continuous memory codes.

- If the engine stalls during the KOER self-test, temporarily increase base idle speed. Reset idle speed following test.

- All trouble codes should be diagnosed in the order they are received.