Codes P0120 and P0420

This forum was recommened by a mechanic. He recommended I ask here about codes: p0120 and p0420. Can anyone help me out.

 

Welcome from SoCal

 

Be patient, hopefully someone will know the answer.

 

Thanks

 

...year...trim level, etc might be helpful?

 

p0120 looks to be a TPS error.
p0420 looks to be a catalytic converter error.

For the TPS, I would at least clean out the Throttle Body first. This is cheap and easy. It may also fix the latter code.

If the TPS is still throwing a code, you can buy a new one. For 2001-2002, the Throttle Body is not really considered to be "serviceable" by the dealer, but you can get the TPS from PartsGeek now.

 

I have a 1999 4Runner that I bought 4 yrs ago. It already had 135,000 miles on it and now it's at 190,000. I'm not sure what TPS is. I did get some advice from a friend to try running a bottle of Cataclean to see if that might help. Someone said they thought one of the codes was for a catalytic converter issue, so I thought it couldn't hurt. How much does a new TPS run?

 

TPS = Throttle Position Sensor. It is connected to the Throttle Body (TB). For your car, it's probably $40. Not sure if I would trust the $10-18 ones I see on Amazon. FWIW, I only buy TOYOTA parts if it's not too crazy expensive. TOYOTA parts run 150k-200k miles...I think they're a good deal.

At your mileage, you really should remove the TB and clean it really well. Then I would replace the TPS and reassemble things with NEW gaskets. Check all hoses in an out of the TB and replace them as needed. I bet you have some vacuum hoses that feel rock hard. They only last so many years (mine went 18). I would also replace the IAC (Idle Air Control) on that car since it is connected to the TB too and because I hear they tend to go (probably another $40 part).

Additionally, when were the plugs and wires replaced? Air filter?

All these things will affect the way the car burns fuel. If it's not burning fuel correctly, then the CAT gets clogged and you get codes thrown. I would fix the first code by doing the above. Clear the codes and drive it for a month. If the cat code p0420 comes back, I would clear it again and see. Sometimes it takes time for the exhaust to come back to normal after fixing the intake.

While I don't think the Cataclean will hurt anything...it's probably not going to do much.

 

P0420 is usually one of three things:

1. Exhaust leak
2. O2 sensors need to replace
3. Catalytic converter(s) need to replace

 

Thanks so much for the much needed advice. I will share it with my mechanic friend and see what he can do to help. Have a great weekend.