Warm Dr-9 - O2 Feedback System Check
- Disconnect 12-pin connector from computer. Connect a voltmeter to connector cavity No. 4 and ground. Voltage reading should be within one volt of battery voltage. If there is zero volts, repair wiring to connector cavity No. 4 for an open circuit to the battery.
- If voltage reading is okay, check terminal in connector cavity No. 4 to ensure it is not spread apart causing a poor connection. Connect voltmeter to the O2 solenoid connector (Green wire) and ground. Disconnect and plug the vacuum hose from the computer.
- Connect a vacuum pump to the computer and apply 14 in. Hg vacuum. Start engine and wait 4 minutes. Raise engine speed to 2000 RPM. Voltage reading should be varying between 4-14 volts. If voltage reading is okay, remove air cleaner lid. Close choke plate. Voltage reading should drop toward zero. If voltage reading is zero volts, go to next step. If voltage reading is 1-3 volts, go to step 12).
- If voltage drops, connect a tachometer to engine. Connect a jumper lead to O2 solenoid (Green wire) and ground. Engine speed should drop. If engine speed drops, proceed to WARM DR-10 . If engine speed did not drop, replace O2 solenoid.
- If voltage reading in step 3) does not drop, disconnect O2 sensor connector. Hold O2 sensor harness terminal in one hand and touch battery positive with the other hand. Voltage should drop. If voltage drops, replace O2 sensor.
- If voltage does not drop, return engine to idle. Turn ignition off. Disconnect 12-pin connector from computer. Connect a voltmeter to the connector cavity No. 11 and ground. Turn the ignition switch to the "RUN" position. Voltage reading should be within one volt of battery voltage.
- If voltage is okay, check the terminal in connector cavity No. 4 to ensure it is not spread apart causing a poor connection. If terminal is okay, replace the computer. If there is zero volt, repair wiring in connector cavity No. 11 for an open circuit to the carburetor 4-pin connector.
- If there is zero volt in step 3), turn the ignition off. Disconnect the 12-pin connector from the computer. Turn the ignition switch to the "RUN" position. Voltage reading should be within one volt of battery voltage. If voltage reading is okay, replace the computer.
- If there is 0-1 volt, turn the ignition off. Disconnect the O2
solenoid connector. Connect an ohmmeter between the O2
solenoid Tan and Green wires (between the solenoid terminals on 4-Bbl. models). The ohmmeter should show some resistance.NOTE: The amount of resistance is unimportant. Just ensure there is some resistance.
- If there is an open circuit, replace the O2 solenoid. If there is resistance, connect a voltmeter to the O2 solenoid connector (Blue wire) and ground. Turn the ignition switch to the "RUN" position. Voltage reading should be within one volt of battery voltage.
- If voltage reading is okay, repair the Green wire to the computer for a short to ground. If voltage reading is not okay, repair the Blue wire for an open circuit to the ignition switch.
- If there is 1-3 volts in step 3), disconnect the PCV valve hose and plug it with your finger. Gradually allow air to enter PCV hose. Voltage reading should increase. If voltage increases, check for fuel contamination in the crankcase. Change oil and filter as necessary. If there is fuel contamination in the crankcase, repair the carburetor.
- If voltage does not increase, disconnect the O2 sensor connector. Hold the O2 sensor harness terminal in one hand and touch the battery positive with the other hand. Voltage should increase. If voltage increases, replace O2 sensor. If voltage does not increase, replace computer.