Test He - Ego Sensor
To prevent replacement of good components, inspect wiring, wiring harness and connectors for visible damage.
- EGO Output Voltage Check: Start and run engine to operating temperature. Unplug EGO sensor and allow engine to idle. Using DVOM on 5-volt scale, connect DVOM between EGO sensor and ground. Raise engine speed to 4000-4500 RPM until DVOM indicates about 0.7 volts. Increase and decrease engine RPM rapidly and note DVOM reading. Reading at 3000-4500 RPM should be 0.5-1.0 volts. Reading at 1000-2500 RPM should be 0-0.4 volts. If readings are correct, proceed to step 4). If readings are not correct, proceed to next step.
- Isolate EGO Sensor Open: Unplug EGO sensor and turn ignition off. Inspect wire from EGO sensor connector for possible opens. If wire is okay, proceed to next step. If wire is not okay, repair wire or replace EGO sensor (if open is between sensor and connector).
- Isolate EGO Sensor Short: Unplug EGO sensor and turn ignition off. Using DVOM on 20-k/ohm scale, measure resistance between EGO sensor connector (sensor side) and ground. If resistance is greater than 10,000 ohms, replace EGO sensor. If resistance is 10,000 ohms or less, repair short in EGO sensor wire or replace EGO sensor.
- EGO Sensor Sensitivity Test: This test step is only for vehicles built after 11/2/87. With EGO sensor connected, start engine. Connect STAR tester adapter cable to STO connector and ground (STI connector open). Raise engine speed to 2500 RPM. If monitor light flashes 8 or more times in 10 seconds, proceed to step 7). If monitor light does not flash 8 or more times in 10 seconds, proceed to next step.
- Check EGO Sensor Circuit: Turn ignition off and install breakout box. Unplug ECA and EGO sensor. Using DVOM on 200-ohm scale, measure resistance between EGO sensor connector (harness side) and pin No. 29 at breakout box. If resistance is greater than 10 ohms, repair open circuit and reconnect EGO sensor. If resistance is 10 ohms or less, proceed to next step.
- Check EGO Sensor Circuit: Turn ignition off and install breakout box. Unplug ECA and EGO sensor. Using DVOM on 200-ohm scale, measure resistance between pins No. 29 and No. 1, 20, 37 and 40. If any of the resistances are less than 10,000 ohms, repair short in EGO sensor circuit to VPWR, VREF, KAPWR or ground. If any of the resistances are 10,000 ohms or more, replace EGO sensor.
- ECA Input Voltage: Start engine and bring to operating temperature. Install breakout box and unplug ECA. Using DVOM on 5-volt scale, measure voltage between pins No. 29 and 49 while increasing and decreasing engine speed between 1500 and 4000 RPM. If reading varies between 0.5-1.0 volts, inspect ECA and ECA connector for damage, looseness, corrosion or damaged pins. If reading does not vary between 0.5-1.0 volts, replace ECA.