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96 Maxima - 145k - P0174 - Fuel System Too Lean Left Bank

All,

The CEL set on my Max two weekends ago showing DTC 0210 (P0174). This indicates that the system detected the left bank was running lean.

Possible faults:

  1. MAF
  2. Injector(s)
  3. Air Intake leak
  4. Bad O2 sensor
  5. Exhaust leak

My diagnosis:

  1. MAF

-> Nope - would likely affect both banks - car runs and pulls fine.

  1. Injector(s)

-> Nope - listened to each injector (left bank is the front 3 cylinders on the VQ30DE) - each clicks normally and at the same frequency. Also, I didn't get any misfire code or feel any hestitation when driving - so I'm pretty sure it's not one or more injectors...

  1. Air Intake leak

-> Nope: I had the top of the engine off two years ago when replacing the valve cover spark plug seals and I replaced the upper-intake- manifold gasket as well as all other intake assembly gaskets. Also I'd expect this to affect both banks.

  1. Bad O2 sensor

-> Most likely. O2 sensors are 60k old - mileage has been down about

10% over the past few months (before CEL tripped)

  1. Exhaust leak

-> Nope: Didn't feel anything upstream of the O2 - no noise.

So before I order myself a new O2 sensor to swap in -> anyone else have any thoughts or comments on my reasoning, or experience with this fault? I'm too lazy to swap the two front O2 sensors around to see if I can move the fault to the other bank :)

I know on the 5th Gens, system lean codes for both banks would show up at the same time, and that was usually the MAF...

Note: Resetting the ECU (to clear CEL) keeps it off for sometimes a few days, sometimes a few hours.

Thanks, Nirav

Reply to
njmodi
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When I had my 98 Maxima, I put a performance catalyst into it, and I vaguely recall getting a similar CEL code. Putting the OEM cat back resolved it. So maybe there's something going on with your cat.

CD

Reply to
codifus

CD - I don't think this is the problem in my case since there is no way after the y-pipe for the ECU to know which bank is lean - there is a single shared O2 sensor after the catalytic converter - but no longer any differentiation per bank.

I still have the factory exhaust on the vehicle.

Thanks for the input.

Nirav

Reply to
njmodi

How about a leaking vacumm hose. Perhaps one that connects to left bank, or affects the left bank.

Al Moodie

Reply to
Al Moodie

That's the thing. It was a bizarre error. Even my situation should not have caused the CEL to come up, but it did. Sometimes computers set off the wrong or very closely related code.

CD

Reply to
codifus

CD - I don't think this is the problem in my case since there is no way after the y-pipe for the ECU to know which bank is lean - there is a single shared O2 sensor after the catalytic converter - but no longer any differentiation per bank.

I still have the factory exhaust on the vehicle.

Thanks for the input.

Nirav

Reply to
njmodi

Follow-up for the benefit of those that are interested:

Swapped out the O2 sensor over the weekend and all is well.

Cheers, Nirav

96 Max GLE, 144k
Reply to
njmodi

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