P0171 help

[Blaine07GT]

07 GT. I was driving along yesterday and my check engine light came on. My x4 said I have the P0171 error code. The guy at AutoZone said either the MAF is bad or i have bad gas. I took off my CAI and removed the MAF and everything appeared to be fine. My car has 120k miles and also has an offroad x pipe. I have also noticed my gas mileage has dropped dramatically (10mpg sometimes) I'm just looking for some more input before I go out and replace the sensor.

 

[BruceH]

It's probably a bad o2 sensor. It's reading lean so the ecu is dumping more gas in. It could also be a loose exhaust manifold but it's unlikely because the stock studs aren't known for loosening up.

P0171 is only for one cylinder bank, a defective maf would affect both.

 

[Blaine07GT]

We also noticed the red tab on the back of the sensor was pulled out

I also recently made my own off road x pipe. We cut the cats off and replaced them with straight pipes. There's a small leak at the bottom of where the stock cats were underneath bank 1. Could the exhaust leak be the problem? It seems like it is far enough away from that 02 sensor but I could be wrong

It's probably a bad o2 sensor. It's reading lean so the ecu is dumping more gas in. It could also be a loose exhaust manifold but it's unlikely because the stock studs aren't known for loosening up.

P0171 is only for one cylinder bank, a defective maf would affect both.

I also recently made my own off road x pipe. We cut the cats off and replaced them with straight pipes. There's a small leak at the bottom of where the stock cats were underneath bank 1. Could the exhaust leak be the problem? It seems like it is far enough away from that 02 sensor but I could be wrong. And it's been working fine for the last month or 2 sense we did that.

 

[BruceH]

We also noticed the red tab on the back of the sensor was pulled out

The maf sensor? That's only a lock, as long as the connector is plugged in it wouldn't make any difference. If the maf was unplugged you would know it.

I also recently made my own off road x pipe. We cut the cats off and replaced them with straight pipes. There's a small leak at the bottom of where the stock cats were underneath bank 1. Could the exhaust leak be the problem? It seems like it is far enough away from that 02 sensor but I could be wrong

I don't think so, it would have to be a pre sensor leak to affect the sensor. You should look up the code to see which bank it's for. If it's for the same cylinder bank as the passenger side it could be that the o2 sensor at the top of the pipe was damaged during your off road pipe conversion.

Did you take the top green o2 sensor out before doing the work?

 

[Dino Dino Bambino]

My x4 said I have the P0171 error code. The guy at AutoZone said either the MAF is bad or i have bad gas.

That's a lean code for bank 1 (passenger side) which, coincidentally, is where you have an exhaust leak. I doubt that the leak is responsible 'cause it's downstream of the sensor but you'll have to seal the leak and see.
If you still have the original factory O2 sensors, they're probably overdue for replacement after 120k miles anyway.
As for the bad gas, could be the hot curry you ate last night.

 

[06redgt]

It's probably a bad o2 sensor. It's reading lean so the ecu is dumping more gas in. It could also be a loose exhaust manifold but it's unlikely because the stock studs aren't known for loosening up.

P0171 is only for one cylinder bank, a defective maf would affect both.

I agree on it probably being the O2 sensor. You could try swapping the sensors putting the left on the right side and vise versa. If the lean code follows the sensor there ya go.

 

[Blaine07GT]

Problem fixed it was the o2 sensor