P0420

[Chris81]

P0420 fault code. Has anyone ever had this problem on their Yaris and what did you do to fix it?

I know I've posted this before but the problem still lingers on with my friends mark 1, 1.0 vvti Yaris. It's had a new cat which cleared the code for 4-5 months, then it came back on again, switched it off and it stayed off for a couple of months, now the MIL is on all the time. Turn it off and it comes on again within a few miles.

Oxygen sensors aren't exactly cheap but is that the best way to go next? Garage have checked exhaust system for leaks and none found. Oh, and p0420 means the engine's running lean. What harm would it cause to leave it as is? Its still running ok.

[gaz9759]

Hi P0420 system too lean, Check for air intake leaks at the pipe from the air filter to the throttle body.

Also check the rocker cover breather pipe, it's under the air filter housing.

Clean the maf sensor, Check that all clamps are tight

Hope this helps

[lc man]

P0420 fault code. Has anyone ever had this problem on their Yaris and what did you do to fix it?

I know I've posted this before but the problem still lingers on with my friends mark 1, 1.0 vvti Yaris. It's had a new cat which cleared the code for 4-5 months, then it came back on again, switched it off and it stayed off for a couple of months, now the MIL is on all the time. Turn it off and it comes on again within a few miles.

Oxygen sensors aren't exactly cheap but is that the best way to go next? Garage have checked exhaust system for leaks and none found. Oh, and p0420 means the engine's running lean. What harm would it cause to leave it as is? Its still running ok.

Hi p0420 unfortunatly its is most likely to be your cat, the 05 3 cylinder yaris suffered from this problem, the cats were replaced and also the spark plugs were changed for a modified ones,p0420 means that the cat efficency is below threshold, i hope this is helpful.