OBD code

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Previously posted under "Light Duty" general section:

 

My "service engine soon" light came on a couple of days ago. Took the truck ('01 GMC Sierra 5.3L) to Autozone to have the code read.

Code was a P1416 which I understand indicates the problem to be a Secondary Air System port side check valve.

Is there a way to check the valve is failing? Could it not also be an oxygen sensor??

Do I have to take the truck into the dealer to have the code cleared or can I just disconnect the wire from the neg battery terminal?

ANY help will be greatly appreciated! thumb.gif

[GM-Tech]

Could it not also be an oxygen sensor??

 

Not at all likely that it's an oxygen sensor. If the sensor was not responsive during the SAI check, it would also be unresponsive at other times, setting an O2 DTC.

 

The check valve is easy enough to check. See if it passes air through one way, but not the other. Lung pressure should be enough to tell. You could also take the hose off and while it's running, see if exhaust is coming out, but if exhaust was leaking back through it, it usually cooks the hose or related components.

 

No, disconnecting the battery won't clear it. Needs to be reset with a scanner.

[p3tweet]

Could it not also be an oxygen sensor??

 

Not at all likely that it's an oxygen sensor. If the sensor was not responsive during the SAI check, it would also be unresponsive at other times, setting an O2 DTC.

 

The check valve is easy enough to check. See if it passes air through one way, but not the other. Lung pressure should be enough to tell. You could also take the hose off and while it's running, see if exhaust is coming out, but if exhaust was leaking back through it, it usually cooks the hose or related components.

 

No, disconnecting the battery won't clear it. Needs to be reset with a scanner.

 

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Thanks for the info. Wasn't sure how the system would know if the check valve was working unless a sensor downstream was sensing it.

[GM-Tech]

Thanks for the info. Wasn't sure how the system would know if the check valve was working unless a sensor downstream was sensing it.

 

That is how it knows. The PCM turns on the air pump and looks for a change in the o2 sensors.

[p3tweet]

Thanks for the info. Wasn't sure how the system would know if the check valve was working unless a sensor downstream was sensing it.

 

That is how it knows. The PCM turns on the air pump and looks for a change in the o2 sensors.

 

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Well if the O2 sensor was bad/faulty could it not appear that something else was bad when in fact the measurment device is the "at fault" part??

How else does the OBD know that the O2 sensor isn't bad?

Don't get me wrong, I'd much rather pay for a check valve than an O2 sensor!!

[GM-Tech]

Well if the O2 sensor was bad/faulty could it not appear that something else was bad when in fact the measurment device is the "at fault" part??

 

The PCM is always monitoring the oxygen sensors, not just when the air pump is commanded on. If you had an o2 problem, you'd get one of several different o2 DTC's, not an air pump DTC. I guess you'll just have to trust me on this one. It ain't an o2 problem.

[p3tweet]

Well if the O2 sensor was bad/faulty could it not appear that something else was bad when in fact the measurment device is the "at fault" part??

 

The PCM is always monitoring the oxygen sensors, not just when the air pump is commanded on. If you had an o2 problem, you'd get one of several different o2 DTC's, not an air pump DTC. I guess you'll just have to trust me on this one. It ain't an o2 problem.

 

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Oh, I trust you. Just trying to understand how the system identifies problems.

Thanks for you help.