Question about 2001 Mitsubishi Eclipse

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01 eclipse i took my car to get it fixed and these are the problem codes that came up: PO421 PO455 PO506 PO123 what does this mean?

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P0 421= Catalytic Converter(s) Below normal flow
P0 455= Evap system leak .. Gas Cap or Carbon cannister or possibly evap lines
P0 123=Drive cycle Incomplete ( no Biggy )
P0506= Idle air control motor..
Doesnt sound like that big of a deal. at our shop.., we'd replace the converter(s) Check the gas Cap for the evap code.. And replace the Idle control motor. The code P0123 should be cleared By ODB2 at that point and should be good to go.. Lemmie know.. Thanks

Posted on Mar 11, 2009


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1 Answer

What dose the code PO421 on misubishi Eclipse 2003 mean

Best Answer: PO 421 is for the heater in the Front O2 sensor for Bank 1. If you have a 6 cylinder it would be the O2 sensor on the side with the number 1 plug wire. If it's a 4 cylinder it's just the front sensor.
I'd buy the sensor from a Mitsubishi dealer, take the VIN number so they can look up the right part. After market O2 sensors are at best a 50/50 chance for the right part.

The ecm compares the outputs of the 02 sensors. 1 is in front of the converter and the other is behind it. When both sensors have somewhat matching readings for 70 seconds PO421 will be set. you have 2 possibilities here- 1- the converter has deteriorated thus the readings are the same. 2-one of the 02s has a bad heater circuit. Have a shop do a converter test and or scan the o2s for proper operations.
Source(s): Mitsubishi Master Tech

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you have the same engine as my 2003 Galant, this should help...

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