Emissions failed at high Idle

2006 TOYOTA YARIS
43,000 MILES • 1.0L • MANUAL
Avatar
KRISHNA1927
  • MEMBER
  • 2 POSTS
Hi all, my car listed above (NCT) failed for CO emissions high at high Idle, everything is fine except CO emission. CO emission at low idle is passed. As per Toyota dealer mechanic recommendation Exhaust back box and air filters were replaced with new one, but CO emission test failed again for same reason. Can anyone suggest what might be the reason for this issue. following are the test results.

First time test results:
Low Idle (779 rpm): CO: 0.23%
HC: 66 ppm

High idle (2780 rpm): Lambda: 0.99
CO: 0.55%
HC: 102 ppm

Second time test results:
Low Idle (780 rpm): CO: 0.02%
HC: 36 ppm

High idle (2680 rpm): Lambda: 1.02
CO: 0.51%
HC: 114 ppm

Can anyone suggest what might be the reason for this issue?
Oct 22, 2017 at 5:29 AM
Advertisement
Avatar
JIS001
  • CERTIFIED EXPERT
  • 3,412 POSTS
Has the check engine light come on? If it has scan it for codes even if the light is not on and post them on here. If no light and codes then you could have a faulty air fuel ratio sensor/oxygen sensor. You will need to have an advance scan tool to read live data and propane to test the sensor.
Oct 22, 2017 at 2:38 PM
Avatar
KRISHNA1927
  • MEMBER
  • 2 POSTS
I verified fault codes using OBD2 scanner, code shown as P0420, but no engine light displayed on dashboard and emission readiness shown as Cata - Incomplete and Oxygen sensor - Incomplete.

Is this means to replace catalytic converter? or oxygen sensor?
Oct 23, 2017 at 3:54 AM
Advertisement
Avatar
JIS001
  • CERTIFIED EXPERT
  • 3,412 POSTS
Very low miles to have a bad catalytic converter already. If you had a bad misfire at some time then yes, sounds like a bad catalytic converter. You should still test the oxygen sensors first to make sure they are okay before replacing the catalytic converter.
Oct 23, 2017 at 7:09 AM