Would a cracked header throw an o2 code?

P0171 and P0132. Thanks.

I've had a cracked manifold and soon there after had to replace the O2 sensor (replaced the manifold at the same time).

Yes, anytime unmetered air gets in the exhaust system you will get funky 02 things happening, of course the p0132 code is most likely a bad 02 sensor

It certainly could. Outside air could come inside the header through the crack and mess up the *read* o2 ratio. Also, the relatively cool air coming in through the crack could eventually cause the o2 sensors to crack.

An air leak would also explain why they're reading too lean.

a cracked header will cause p0171 o2 too lean. a p0132 is an open in the heater cicuit of the sensor. replace the craked header and o2 sensor

Thanks!

OnorOffroad said:

P0171 and P0132. Thanks.

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Do you have a cracked header?

Milford Cubicle II said:

It certainly could. Outside air could come inside the header through the crack and mess up the *read* o2 ratio. Also, the relatively cool air coming in through the crack could eventually cause the o2 sensors to crack.

An air leak would also explain why they're reading too lean.

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Could you explain to me (I'm kind of slow) how outside air (ambient pressure) would get into the exhaust through a crack when the air pressure inside the exhaust is higher than that of the outside air...oh yes, with the engine running .

Sidewinder CC said:

Could you explain to me (I'm kind of slow) how outside air (ambient pressure) would get into the exhaust through a crack when the air pressure inside the exhaust is higher than that of the outside air...oh yes, with the engine running .

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It is a time domain issue. The air goes through the exhaust pipe in pulse waves, as the exhaust valves open and close. That high pressure pulse moves through the exhaust pipe like an ocean wave on the beach, but like an ocean wave, it reverses course at some point......

As that pulse moves down the pipe, and as the pressure in the exhaust stroke of the piston falls towards ambient, the pulse has enough momentum to actually draw a vacuum on the combustion chamber near the end of the exhaust stroke. That low pressure part of the wave front in the exhaust pipe is when ambient air can be sucked into the exhaust manifold.

Also, the O2 sensor measures the difference in O2 concentration between the inside and outside of the exhaust pipe, so if the high pressure wave pulse blows exhaust air out the crack near the outside of the O2 sensor it will change the outside of the pipe concentration and screw up the measurement as well.