1999 Tahoe check engine light HELP!!!!!

[rdharley3]

My 99 Tahoe's computer is giving a trouble code of 420 Catalytic trouble bank 1. I was told to check the catalytic converter off the drivers side manafold, check the O2 sensors, tune-up, replace pcv valve, and run on premium fuel W/recommended additive (Sea foam).

I took the tahoe to a muffler shop they checked both converters (heat tested) and told me they were fine, they also stated that 420 was not the trouble code indicating bad O2 sensors so they feel like they were not the problem. I changed the plugs, plug wires, distributor cap, rotor button, air filter, pcv valve, and run high octane fuel w/ additive (sea foam) and still I have the same problem.

The Tahoe runs great the only problem is that we have to VET test our vehicles and reguardless of what your emmissions are with that code they will not pass it, and you cannot get a waiver after spending xxx amount of dollars trying to fix it, You fix it of no tags.

I don't know what else to do any suggestions would be greatly appreciated.

RDH

[GMMerlin]

Originally Posted by rdharley3

My 99 Tahoe's computer is giving a trouble code of 420 Catalytic trouble bank 1. I was told to check the catalytic converter off the drivers side manafold, check the O2 sensors, tune-up, replace pcv valve, and run on premium fuel W/recommended additive (Sea foam).

I took the tahoe to a muffler shop they checked both converters (heat tested) and told me they were fine, they also stated that 420 was not the trouble code indicating bad O2 sensors so they feel like they were not the problem. I changed the plugs, plug wires, distributor cap, rotor button, air filter, pcv valve, and run high octane fuel w/ additive (sea foam) and still I have the same problem.

The Tahoe runs great the only problem is that we have to VET test our vehicles and reguardless of what your emmissions are with that code they will not pass it, and you cannot get a waiver after spending xxx amount of dollars trying to fix it, You fix it of no tags.

I don't know what else to do any suggestions would be greatly appreciated.

RDH

First...DO NOT use high octane gas in your vehicle..it was designed to run on 87 octane and using higher octane could cause undesireable driveability concerns.
Read here for more info

Secondly, the code P0420 is for catalyst efficency, meaning that the catalyst cannot convert the HC and other pollutants. The only repair is to replace the converter (which is covered under a 8/80 warranty)
A heat test is NOT a valid test to determine whether or not a converter is working properly.

[maintainin76]

Merlin is right. It is a bad cat. Mine had the same code. If you have under 80k on the truck, take it to the dealer. They'll replace them at no cost to you.

[rdharley3]

Thanks for the info. I had the cat replaced and all is fine.


RDH