emmission codes on 1997 Chevrolet Monte Carlo

do u know what the code po121 means for 97 monte carlo 3.1 v6? or po420 on 98 merury sable?

by in La Porte, TX on January 22, 2011
1 answer
ANSWER by on January 27, 2011
The p0121 on the monte carlo is a throttle position fault. More testing would be needed to determine if the sensor is actually bad. The p0420 on the mercury is a catalytic converter fault. Most likely indicating the converter should be replaced.
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my monte carlo check engine light came on and it stayed on. i'm trying to figure out what is wrong because i had got my oil changed last sat on time and i keep the maintence up on my car.