4Runner4Christ

I have a 99 4runner (84K miles) and my check engine light came on after a recent drive to Chicago. Upon getting home I had the dealer diagnose it as a code po-420. They turned off the light thinking it could possibly been some bad gas, but it came back on reletively quickly. I took it back again and this is what they said:

The scan found code po-420, catalyst system efficiency below threshold. Truck needs catalytic converter and both O2 sensors replaced. Total cost $1687.20. Yikes!

I really dont want to fork out that kind of cash. What do you guys think? Some other options I can think of:

1. Assuming the part numbers are the same...go to the junkyard and find a '01 or '02 Runner and buy that.
2. Buy an aftermarket cat-back system. Do they include the cat?

Any input or other options would be appreciated!

MTL_4runner

The P0420 is usually a bad cat converter. They become inefficient and do not register properly thru the rear o2 sensor. The cat/cats are 8yr/80k mileage warranty. I would take it to the dealer and have it looked at and replaced. If you have more than 80K miles. Have it replaced anyway, it will eventually cause problems. Most reputable exh shops have replacement cats at a reasonable price.

Your code is P0420 Catalyst System Efficiency Below Threshold (Bank 1) so your choices would be:
1) Go to the junkyard and get the parts from a 99-02 4runner (verify parts interchange at the dealer)
2) Get an aftermarket CAT for your truck (available from a few sources)

I did read one person say it was a MAF sensor causing that code too but I would start with the converter first, the MAF usually throws a P0171 code when it needs cleaning. Most of the time cleaning the MAF sensor will take care of the p0171 code.

4Runner4Christ

I wanted to post an update to this thread. Based on various recommendations I decided to start with replacing the air/fuel ratio sensor that goes in front of the first cat (part# 89467-35011 which cost me $202) and the oxygen sensor that goes in after the second cat (part# 89465-49105 which set me back $108). I had the check engine light shut off after replacing these sensors and it has been three days now and the light has not come back on. I am keeping my fingers crossed that my issue is resolved with this $300 repair. Like I mentioned above the dealer wanted $1600 to replace the whole system.

Gadget

The next time you need replacement O2 sensors you might want to check out the kick ass prices on real DENSO sensors at

www.URDUSA.com

Gadget

yamarocket630

P0420 is set by a failed catalyst, but the catalyst rarely fails for no reason. It was usually poisoned by comtamination, or overheated by a rich air/fuel mixture. The bad news is that the DTC will come back. If it failed once, it will fail again. Think about it this way, cats are expensive, so you can be sure that Toyota made that diagnostic really reliable.