WpgWelder

So I just recently bought (private sale) a minty 2001 Tacoma ext cab, automatic with the 3.4L V6.
after about 80 miles the engine light comes on, so I take it to my mechanic and scans it. Gives me this error code: "P0420B".
The truck is originally from California according to the guy I bought it from.
Now that it's in colder weather (Winnipeg MB, Canada) it seems to be acting up.
My mechanic says it's probably an o2 sensor, but reading everything on here says it's the Cat. Is this gonna affect my fuel mileage?
I'm getting real crappy mileage atm.
Is it the o2 sensor/sensors? or is it the cat?

wyoming9

iTrader: (1)

The sensor is much cheaper to try then the cat.

change the rear one see what happens.

WpgWelder

actually the upstream sensor is double the cost of the front cat.
I replaced the front cat and already I've doubled my fuel mileage.
Was getting 125 miles/tank, i'm at half tank now and just under 125 miles.
gonna see about rear cat and the 2 sensors. rear cat is not needed in Canada, but gotta keep it on for the sensor.

ahmad1

Error Code: P0420
Fault Location:
Catalytic Converter System, Bank 1 - Efficiency Below Threshold
Possible Cause:
Leakage in Intake and/or Exhaust System.
Catalyst faulty.
Oxygen Sensor(s) faulty.
Oxygen Sensor(s) Control faulty.

Possible Solutions:
Check Intake and Exhaust System for Leaks.
Check Catalyst.
Check Oxygen Sensor(s).
Check Oxygen Sensor(s) Control.
Perform Oxygen Sensor(s) Aging Check.

504runner

I have been having a surging problem for a while now to where the 4runner really struggles to get past 1700-2000 rpms. I can push it past 2000 rpms if i put the pedal down to the floor, there to where it sounds like the engine is running very loud and fast, but not making the car go faster. It's a classic 0420 code saying it's the cat, but like everyone says check the sensors first. My questions are:

1. can you use a used sensor salvaged from another truck, and if I try could this hurt anything else? Also, if this doesn't fix the problem, is the original sensor trash now that it has been removed?

2. If i need to purchase a new sensor, is it very important to buy OEM (like $90-130) or can I get a 3rd party for much cheaper. Basically how important is it to stay away from 3rd party with this particular product?

3. Would you suggest changing the front or back sensor first?

Thanks for reading, I appreciate anyone's help with this issue.

TheDurk

1. Yes, and no and no. Swap to your heart's content.

2. It is important to buy Denso ONLY, but it doesnt have to be from Toyota.Go to http://densoautoparts.com/find-my-pa...icle-selection to get your Denso part number, then get it from Amazon, RockAuto or wherever it is cheaper. Googling the Denso part number works well, but Amazon usually wins.

3. For a P0420, you would normally do the rear sensor first. However, since you have performance issues and a P0420, you may have a badly plugged cat, or it could be a bad front sensor. The rear sensor has no effect on performance. So, in your case, it's kind of a coin toss.

As far as the used sensor thing goes, any front or rear sensor off a 3G 4Runner that will bolt up and plug in will function for you; the only differences is wire length. If the plug doesn't fit in the rear, it's an A/f sensor and might work in front if you have Cali.-type emissions or an '01-'02. Very late 4Runners ('01-'02) used the screw-in rear o2 sensors instead of the flange type sensors.