98 IS GIVING ME P0420 AND P0125

1998 GMC Savana



April, 9, 2012 AT 6:27 AM

98 GMC savana is giving me P0420 and P0125 is there one thing that can give both codes or are there different things wrongs with it. Given the year / model what are the most probable causes.

Thank You

1 Answer



April, 9, 2012 AT 6:49 AM

P0125 coolant temp to low for closed loop mode. P0420 catalyst efficiency below threshold. I would fix the first and see if the second goes away. Could be your thermostat or the temp sensor.

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