Troubleshooting Oxygen Sensor on a 94 Toyota 22RE
- 1). Run your Toyota for about 20 minutes to bring the engine to operating temperature so the oxygen sensor starts monitoring the exhaust stream.
- 2). Park your Toyota on level ground, turn off the engine and go get your 10 megaohm digital voltmeter.
- 3). Set your meter to a low DC volt range so that you can read from 0.1 V up to 1.0 V.
- 4). Open the hood and start the engine. Race it above 1,200 rpm for two minutes and then let it idle. Begin your tests by connecting your meter red probe to the sensor signal wire and the black probe to any metal surface or bolt on the engine. The voltage reading on your meter should fluctuate rapidly between 0.2 and 0.8 volts.
- 5). Disconnect a vacuum hose at the intake manifold, like the one going to the Positive Crankcase Ventilation (PCV) valve. The display on your meter should go down to about 0.2 volts, signaling the computer that there is very low fuel in the mixture. Reconnect the vacuum hose.
- 6). Detach the air cleaner tube with a Phillips-head screwdriver and block the opening leading to the throttle body with a shop rag. The display on your meter should go up to about 0.8 volts, signaling the computer there is too much fuel mixture. Replace the air cleaner tube with the Phillips-head screwdriver.
- 7). Snap the throttle open and close. The display on your meter should cycle up and down, responding to the sudden surge of air going through the throttle. Ask your assistant to shut off the engine. If you noticed the sensor cycling slowly during the first test or the sensor failed to respond appropriately to the mixture tests, check the wires in the circuit for shorts or breaks. If not, replace it.
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