Take the 2-minute tour ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.

2003 Ford Crown Victoria
V8 Engine
Dual exhaust
2 cats & O2 sensors per side

Since some time last year I've been getting an error code throw up, with seemingly no regularity:

P2197 - O2 stuck lean - Bank 2 Sensor 1

First thought was to replace the sensor, so that's new but didn't fix the problem. It doesn't happen much when it's hot and dry, primarily when it's cold and/or damp out.

I recently picked up a bluetooth OBD-II live scanner, and looking at the values as I drive, I've learned that, when it does happen, the O2 voltages are pretty much normal, though they'll kind of "stick" on B2-S1 to a number (different each time) whereas B1-S1 will fluctuate normally. I've seen anywhere from .06v to .94v

At the same time, the short-term fuel trim will lock even tighter to a number, and stay that way until it all clears. Most common is 32.8%, but there is some variance from about 30% - 55%.

It'll start normally, then within about 10-30 seconds lock onto these numbers, stay that way for about a minute, then return to normal ranges for both voltage and trim. If the car is started cold then it won't throw a code, but if it's still warm then it will often trigger the MIL and store the freeze-frame data.

Any ideas on what's actually wrong, how to fix it, or more diagnostics to do?

My #1 thought is a vacuum leak somewhere, and I have an idea of which chunk of hose it might be, but I haven't had a chance to find a new one to replace it with. My other thought is the computer having some values stored wrong that I would need to reset (just disconnect the battery). I only thought of this one a day ago and haven't had the time to do it yet and still go on a long enough drive to relearn shift points.

share|improve this question
add comment

1 Answer 1

From everything I see in this paper, it seems that it may be related to a vacuum leak.

tl;dr - Check your vacuum lines and make sure none of them are cracked.

P2197 Page 1 P2197 Page 2 P2197 Page 3

Here are some more ideas from here:

P2197

Lack of HO2S-21 Switch, Sensor Indicates Lean Detailed Description A heated oxygen sensor (HO2S) indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.

Possible Causes:

Electrical:

  • Short to VPWR in the harness or HO2S.
  • Water in the harness connector.
  • Open/shorted HO2S circuit.
  • Corrosion or poor mating terminals and wiring.
  • Damaged HO2S.
  • Damaged powertrain control module (PCM).

Fuel System:

  • Excessive fuel pressure.
  • Leaking/contaminated fuel injectors.
  • Leaking fuel pressure regulator.
  • Low fuel pressure or running out of fuel.
  • Vapor recovery system. Induction System:
  • Air leaks after the mass air flow (MAF) sensor.
  • Vacuum Leaks.
  • PCV system.
  • Improperly seated engine oil dipstick.

EGR System:

  • Leaking gasket.
  • Stuck EGR valve.
  • Leaking diaphragm or EVR.

Base Engine:

  • Oil overfill.
  • Cam Timing.
  • Cylinder compression.
  • Exhaust leaks before or near the HO2S(s)
share|improve this answer
    
If it's just on a single bank, vacuum leak is the first place to look for sure. –  Brian Knoblauch Oct 31 '12 at 16:38
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.