TEST 2: Inducing A Lean Condition
In this test section, you'll induce a Lean air/fuel mixture to see if th O2 sensor reacts to it.
What you're looking for is for the O2 sensor to report a voltage as close to 0.100 as possible.
Alright, this is what you'll need to do:
- 1
Start your vehicle and let it idle for about 15 minutes. This will allow the engine to warm up and activate the O2 sensor.
- 2
Connect your scan tool and get to its Live Data mode.
- 3
Scroll down to the PID that's labeled O2S11. This PID will show you the oxygen sensor voltage activity.
- 4
You should see the O2 sensor voltage numbers moving between 0.100 and 0.900 Volts constantly.
If the voltage value stays fixed, don't worry about this yet, continue to the next step. - 5
With the engine running, slightly disconnect the vacuum hose the connects to the brake vacuum booster while observing the scan tool.
You don't need to remove the vacuum hose completely or you'll make the engine stall. - 6
You should see the O2S11 voltage values immediately drop to 0.100 Volts.
- 7
Reconnect the vacuum hose and let the engine idle for about 1 minute.
- 8
The O2 sensor values should start to oscillate between 0.100 Volts to 0.900 Volts.
OK, the test is done, let's take a look at what your test results mean:
CASE 1: O2S11 voltage numbers dropped to 0.100 Volts. This is the correct and expected test result and it lets you know that the O2 sensor is reacting to the Lean condition you induced.
If the O2 sensor passed TEST 1 and TEST 2 you can conclude that the O2 sensor is good. Some other component is causing the PCM to think the O2 sensor is fried.
Go to the section: Oxygen Sensor Codes Keep Coming Back.
CASE 2: O2S11 voltage numbers DID NOT drop to 0.100 Volts. This confirms that Bank 1 Oxygen Sensor 1 has failed. You can replace the oxygen sensor.
Oxygen Sensor Codes Keep Coming Back
So you tested the oxygen sensor and they tested good or you have already replace one or both and yet the PCM keeps accusing them as being bad (which also means that the check engine light is back on).
When this happens, it's usually due to either a Rich condition or Lean condition that's being caused by some other component on the engine.
What sucks about this, is that whatever is causing the Rich or Lean condition is not present all of the time (specially when you're conducting the tests). This happens quite a bit. The strategy here is to wait a few days for the condition (that's causing the O2 sensor issues) to get worse. When this occurs, you'll be able to test it and solve it.
More Test Articles
I've written quite a few 2.4L ‘how to’ tutorials that may help you troubleshoot the issues on your 2.4L Nissan Altima, Xterra, Frontier. You can find the complete list at: Nissan 2.4L Index Of Articles.
Here's a sample of the Nissan 2.4L articles you'll find:
- How To Test Engine Compression (Nissan 2.4L, 2.5L).
- How To Test The Fuel Injectors (Nissan 2.4L).
- How To Troubleshoot A Blown Head Gasket (Nissan 2.4L, 2.5L).
- How To Test The Ignition System: 2.4L Nissan Altima (1993-1997) (at easyautodiagnostics.com).
If this info saved the day, buy me a beer!
