P0161 B2S2 After Magnaflow Exhaust Install

Hey All,

So I just replaced my 2002 exhaust with a complete Magnaflow system from down pipe cats through tail pipe. Truck has nice purr and everything went smooth. Only issue is now I'm throwing a P0161 on bank 2 sensor 2. The O2 sensor looked fine and reinstall was no problem on a new pipe.

An important thing to mention is my truck is an east coast vehicle with 2 cats and a resonator. I unknowingly installed the intermediate pipe from Magnaflow (Only one they make) that apparently is also now a third cat as opposed to the resonator. I guess I thought the original was also a cat as opposed to just a resonator. So, can introducing a third cat cause this issue - anyone also have this happen?

I have no problem buying a new O2 sensor but just want to be sure this is not going to be a continuous issue with the third cat. I will probably also ask Magnaflow this week.

Thanks for any help you could lend,
Steve

 

No, it shouldn’t. My truck is a two CAT truck from NH when I bought it new. A third CAT only affects emissions after the O2 sensors, so no worry. IIRC the P0161 is for the heater circuit on the O2 sensor. It might have been right on the edge of failing before you did the work. Replacing the sensor should fix it. Just make sure you get genuine Denso replacements, the OE manufacturer. You can buy them cheap on Rockauto.com. Many here already have.

 

Thanks for the quick reply! That makes sense I will go for the sensor then. On Rockauto it looks like both bank's sensor 2 (rear) are the same part?
-Steve

 

Yes, they are. Typically you replace them in pairs unless you like doing it once at a a time since the other side being the same age will probably fail in a couple of years.

 

First off, be careful with sensor brand. Only Denso, or if you absolutely can't get Denso, Bosch can work, but Denso is preferred.

Second, if your truck has 4.7L. your sensor part number varies depending whether you're 2WD or 4WD. In your truck info, you failed to include which engine and which drivetrain you have. RockAuto may not tell you that, but I am, because Denso clearly indicates this below.

Here are your part numbers. Because the part numbers are identical down downstream (just differ based on drivetrain), if you want to do a quick test, swap the driver and passenger side downstream sensors and clear codes. If the code changes to P0141, you know the sensor (that's now on the driver downstream) is bad.

However, ideally, you want to change sensors in pairs (upstream/downstream). Or, if you just want to fire and forget for another 20 years, just replace all four.

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