Emissions failed at high Idle

KRISHNA1927

MEMBER
2006 TOYOTA YARIS
1.0L
MANUAL
43,000 MILES

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?

3 Replies

JIS001

MECHANIC
3,408 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.

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Sunday, October 22nd, 2017 AT 2:38 PM

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?

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Monday, October 23rd, 2017 AT 3:54 AM

JIS001

MECHANIC
3,408 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.

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Monday, October 23rd, 2017 AT 7:09 AM