You will need to find out what codes are being set with the check engine light, a scan tool is best, here is an alternative way to test.

Reading Codes With Analog Voltmeter

See Figures 5 and 6

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Fig. 5: Correct hookup to read codes with a voltmeter

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Fig. 6: Code display patterns on an analog voltmeter

In the absence of a scan tool, an analog voltmeter may be used to retrieve stored fault codes. Set the meter range to read DC 0-15 volts. Connect the + lead of the meter to the battery positive terminal and connect the - lead of the meter to the self-test output pin of the diagnostic connector.

Follow the directions given previously for performing the KOEO and KOER tests. To activate the tests, use a jumper wire to connect the signal return pin on the diagnostic connector to the self-test input connector. The self-test input line is the separate wire and connector with or near the diagnostic connector.

The codes will be transmitted as groups of needle sweeps. This method may be used to read either 2 or 3-digit codes. The Continuous Memory codes are separated from the KOEO codes by 6 seconds, a single sweep and another 6 second delay.

Reading Codes With MIL

See Figures 7 and 8

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Fig. 7: Only a jumper wire is needed to read codes through MIL or the message center

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Fig. 8: Code display pattern using the dashboard warning lamp

The Malfunction Indicator Lamp on the dashboard may also be used to retrieve the stored codes. This method displays only the stored codes and does not allow for any system investigation.

Follow the directions given previously for performing the KOEO and KOER tests. To activate the tests, use a jumper wire to connect the signal return pin on the diagnostic connector to the self-test input connector. The self-test input line is the separate wire and connector with or near the diagnostic connector.

Codes are transmitted by place value with a pause between the digits; Code 32 would be sent as 3 flashes, a pause and 2 flashes. A slightly longer pause divides codes from each other. Be ready to count and record codes; the only way to repeat a code is to re-cycle the system. This method may be used to read either 2 or 3-digit codes. The Continuous Memory codes are separated from the KOEO codes by 6 seconds, a single flash and another 6 second delay.

To perform the KOER test:

1. Hold in all 3 buttons, start the engine and release the buttons.

2. Press the SELECT or GAUGE SELECT button 3 times. The message dealer 4 should appear at the bottom of the message panel.

3. Initiate the test by using a jumper wire to connect the signal return pin on the diagnostic connector to the self-test input connector. The self-test input line is the separate wire and connector with or near the diagnostic connector.

4. The stored codes will be output to the vehicle display.

5. To exit the test, turn the ignition switch OFF and disconnect the jumper wire.

Other Test Modes

CONTINUOUS MONITOR OR WIGGLE TEST

Once entered, this mode allows the operator to attempt to recreate intermittent faults by wiggling or tapping components, wiring or connectors. The test may be performed during either KOEO or KOER procedures. The test requires the use of either an analog voltmeter or a hand-held scan tool.

To enter the continuous monitor mode during KOEO testing, turn the ignition switch ON. Activate the test, wait 10 seconds, then deactivate and reactivate the test; the system will enter the continuous monitor mode. Tap, move or wiggle the harness, component or connector suspected of causing the problem; if a fault is detected, the code will store in the memory. When the fault occurs, the dash warning lamp will illuminate, the STAR tester will light a red indicator (and possibly beep) and the analog meter needle will sweep once.

To enter this mode in the KOER test:

1. Start the engine and run it at 2000 rpm for two minutes. This action warms up the oxygen sensor.

2. Turn the ignition switch OFF for 10 seconds.

3. Start the engine.

4. Activate the test, wait 10 seconds, then deactivate and reactivate the test; the system will enter the continuous monitor mode.

5. Tap, move or wiggle the harness, component or connector suspected of causing the problem; if a fault is detected, the code will store in the memory.

6. When the fault occurs, the dash warning lamp will illuminate, the STAR tester will light a red indicator (and possibly beep) and the analog meter needle will sweep once.

OUTPUT STATE CHECK

This testing mode allows the operator to energize and de-energize most of the outputs controlled by the EEC-IV system. Many of the outputs may be checked at the component by listening for a click or feeling the item move or engage by a hand placed on the case. To enter this check:

1. Enter the KOEO test mode.

2. When all codes have been transmitted, depress the accelerator all the way to the floor and release it.

3. The output actuators are now all ON. Depressing the throttle pedal to the floor again switches the all the actuator outputs OFF.

4. This test may be performed as often as necessary, switching between ON and OFF by depressing the throttle.

5. Exit the test by turning the ignition switch OFF, disconnecting the jumper at the diagnostic connector or releasing the test button on the scan tool