Sensor

High voltage on downstream O2 sensor after driving, but low voltage on idle

High voltage on downstream O2 sensor after driving, but low voltage on idle
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  • Leo Dorsey
  1. What should the downstream O2 sensor read at idle?
  2. What voltage should downstream O2 sensor read?
  3. What are the symptoms of a bad downstream O2 sensor?
  4. Why does O2 sensor read High Voltage?
  5. How do I know if my upstream or downstream oxygen sensor is bad?
  6. What does the downstream oxygen sensor control?
  7. Why does my O2 sensor read 0 volts Silverado?
  8. What voltage should O2 sensor be?
  9. How do you test a downstream oxygen sensor?
  10. Which O2 sensor goes bad first upstream or downstream?
  11. Does downstream O2 sensor affect performance?
  12. Can I drive without downstream O2 sensor?

What should the downstream O2 sensor read at idle?

To test for air leaks, after engine is warmed up and idling, unplug the IAC(idle air control) Valve, idle should drop down to 500rpm, barely running, or engine may even stall, either is good it means no vacuum leak. If idle stays high then you do have a leak.

What voltage should downstream O2 sensor read?

When the engine is first started, the downstream O2 sensor's output will mirror that of the upstream O2 sensor, and flip-flop back and forth between rich and lean. Once the converter lights off, the downstream O2 sensor will settle down and “flat-line” at a steady voltage reading usually around 0.45 volts or so.

What are the symptoms of a bad downstream O2 sensor?

Here are some of the most common signs that your oxygen sensor is bad.

Why does O2 sensor read High Voltage?

The high voltage condition from the O2 sensor is indicating a lack of oxygen in the exhaust or other related problems, such as a leaking fuel injector or a broken up catalyst inside.

How do I know if my upstream or downstream oxygen sensor is bad?

The downstream or diagnostic sensors only monitor the exhaust leaving the catalytic converter and will not cause such an issue. Other symptoms of a bad oxygen sensor include a rough idle, a misfire, and/ or hesitation when trying to accelerate.

What does the downstream oxygen sensor control?

Oxygen Sensors, commonly referred to as O2 sensors, are part of your vehicles emission system. The purpose of the downstream, after converter, sensors is to monitor the quantities of harmful exhaust gases flowing into and out of the catalytic converter to ensure the converter is working properly.

Why does my O2 sensor read 0 volts Silverado?

Either the O2 sensor is bad or you're running too lean. The fact that fuel trims haven't updated just means the ECU hasn't gone into closed loop yet...which makes sense given the lack of an O2 reading. Try richening your injector compensation and see if you can get the O2 sensor to move.

What voltage should O2 sensor be?

The Downstream Oxygen Sensor (Oxygen Sensor 2)

Therefore, the downstream oxygen sensor (sensor 2) should produce a steady voltage of approximately 0.45 volts.

How do you test a downstream oxygen sensor?

Oxygen Sensor Test

  1. Identify the specific o2 sensor that you want to do the oxygen sensor test on. ...
  2. You will need a 10-megaohm impedance digital voltmeter for testing the o2 sensor. ...
  3. Now start the car and let it run until it reaches operating temperature. ...
  4. Once you have reached operating temperature, turn off the engine.

Which O2 sensor goes bad first upstream or downstream?

The upstream oxygen sensor is situated before the catalytic converter whereas the downstream oxygen sensor is located after the catalytic converter. Knowing the location of the oxygen sensor at fault is important. The number and location of the oxygen sensors are specific to every vehicle's year, make and model.

Does downstream O2 sensor affect performance?

If the downstream O2 sensor has a tendancy to stay above center, the PCM will set a low goal voltage which results in a lean fuel mix which can cause the engine to run hotter and aggravate a spark knock condition.

Can I drive without downstream O2 sensor?

Short answer... yes. The rear O2 sensors are emissions related only. You will have an error light but it won't harm anything.

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