Oxygen Sensor
- When the odometer shows 60,000 or 120,000 miles, the oxygen sensor light on the instrument panel will flash. If not, there is a malfunction and system should be tested.
- Remove ECM from behind dashboard, leaving coupler attached. Warm engine to normal operating temperature. Run engine at idle speed. Using a voltmeter, connect probes to terminal No. 10 (oxygen sensor) and terminal No. 21 (ground). See Fig 1 .
- Accelerate the engine from idle to 1500-2000 RPM. Voltmeter should read between .0-.8 volts depending on engine speed. If voltmeter gives proper reading, then oxygen sensor is sending correct input to ECM unit. If voltmeter indicator does not deflect between .0-.8 volts, see following lists for paossible causes:
Remains at Zero.
- O(2) Sensor Wire Loose
- Intake System Leaky
- Mixture Too Lean
- Carburetor Malfunction
- Voltmeter Resistance Too Low
- Oxygen Sensor Defective
Remains at .8 Volts.
- Choke On, Engine Cold
- Thermal Switch Defective
- MCS Disconnected
- MCS Valve Defective
- To check feedback to oxygen sensor from the ECM, turn oxygen sensor light switch off. See Figure . Using an ohmmeter, connect positive probe to body ground and negative probe to terminal No. 17 of ECM unit. Ohmmeter indicator should deflect. If not, reverse polarity of ohmmeter probes. Turn oxygen sensor light switch on. Sensor light should flash. If not, wiring harness, light bulb or oxygen sensor switch may be defective.
Fig 1: Checking Oxygen Sensor Signal NEVER use an ohmmeter to test oxygen sensor circuit. Courtesy of Suzuki of America Corp.
ELECTRONIC CONTROL MODULE FEEDBACK SENSOR CHART
| Sensor/ Terminal No. | Ohmmeter Reading | Condition | |
|---|---|---|---|
| Thermal Switch | |||
| 4 | Zero | When Coolant Temperature is Less Than 116°F (46.5° C) | |
| 4 | Infinite | When Coolant Temperature is Above 116°F (48.5° C) | |
| Idle Microswitch | |||
| 15 | Zero | Engine Warm, Accelerator Not Depressed | |
| 15 | Infinite | When Accelerator is Depressed | |
| High Altitude Compensator | |||
| 14 | Zero | Altitude is Above 4000 Ft. (1220 m) | |
| 14 | Infinite | Altitude is Below 4000 Ft. (1220 m) | |
| Thermal Engine Room Switch | |||
| 11 | Zero | Engine Room Temperature is Below 67°F (19.5°C) | |
| 11 | Infinite | Engine Room Temperature is Above 67°F (19.5°C) | |
| Wide Open Throttle Switch | |||
| 5 | Zero | Accelerator Pedal Slightly Depressed or Not Depressed | |
| 5 | Infinite | When Accelerator is Completely Depressed | |
| Fifth Switch | |||
| 19 | Zero | When Shifted Into Fifth Gear | |
| 19 | Infinite | When Shifted Into All Gears Except Fifth | |