Need some advice...

[cobhobaroblobie]

Check engine light on.


2000 3.4L V6 4x2 4runner

CODES: P0171 lean bank 1. P420 Cat Low.

Things I've done: Replace spark plugs, Cleaned out Air Filter, Cleaned M.A.F. sensor. Compression test on cylinders all within 10 psi, Checked resistance on ignition coils & spark plug wires, all within specs. I've been treating the fuel system with LUCAS.

The check engine light has come off and on 2xs the past 600 miles.

Though I was able to pass smog by pulling my computers fuse out for a couple seconds. Just annoying to see that its burning an orange image into my eyes.


Any Ideas...

 

[4-Ripcord]

Front O2 sensor. Almost always the cause of those codes iirc.

Oxygen / AFR Sensors - Underdog Racing Development

 

[fish0281]

Changing the O2 sensors is relatively cheap and easy, so it's worth a shot. I would not be surprised if your CCs have bitten the dust though (especially if you've got higher mileage).

 

[T4R_Finally]

For a straight p0420 code, i would say try changing the rear o2 sensor. Given that code with another from the upstream sensor, maybe bad cat system or exhaust leak. Sensors are easy and cheap enough to change and see what happens though. Replacing the rear one with a $62 denso from ebay got rid of my p0420.