[slk230mb]

P0174 Fuel Trim System Lean Bank 2

Been getting a PO174 on and off for a few weeks, sometimes with a couple hundred miles in between.

I'm going to change the air filter, but was wondering if anyone had the GM part numbers for the front O2 sensor and MAF in case I need to get those too. I'm off warranty and want to avoid a trip to the dealership if I can.

Oh, and is Bank 2 the left or right?

 

[TimmyC]

Bank 2 is left (driver's side)

Check for leaks in the ducting between the air filter and the throttle body. That would be my guess.

 

[slk230mb]

Thanks. I'm going to replace the filter tomorrow and check for leaks. It shouldn't be rainy tomorrow.

 

[Frnkbooth]

Agreed with TimmyC. This is a leak. Getting extra air in somewhere causing ECU to increase fuel trim. Same code on a 98 lincoln years ago. Leak in the vac
line due to a cracked plastic T connector hidden under a cover. Hard to find as it comes and goes.

 

[SQPL seville]

I had the same issue as you. It was a broken pipe fitting at the intake.

 

[06WhiteDiamond]

Just had the car in at dealer for the same code. I believe they replaced both o2 sensors.

 

[PORGUY]

Bank 2 is left (driver's side)

Check for leaks in the ducting between the air filter and the throttle body. That would be my guess.

^^^^^^ what he said...

 

[Rboughne1]

Just got this code yesterday. Finally hit 80 degrees here around the PHL/NYC area, and when the car got up to temp, the code popped. Figured it was the expansion/contraction of the boot on the TimmyC intake to the pipe, as I installed it in 40 degree weather. Reinstalled it, tightened everything up, touched the positive cable to the black terminal to clear the codes, and success, no code when I re-ran the absolute SH!T out of it. Funny though, how it comes up lean bank 2. Why wouldn't Bank 1 scream lean as well?

 

[TimmyC]

Bank 2 (left) always runs leaner than Bank 1.

 

[Rboughne1]

Bank 2 (left) always runs leaner than Bank 1.

Any idea why Timmy? Everything's port injection, so why would the banks differ?

 

[TimmyC]

Don't know. I've seen it on many LC3 motors.