Strange Trouble code
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Strange Trouble code
I have a 2001 Mazda 626 4 cyl. auto 73K. Check engine light came on. code showed PO421. "Warm up catalyst efficiency for bank 1 below threshold for engine operating conditions. " Where do I go from here. Autozone suggested changing thermostat, but not a convincing opinion. Should I start there with the thermostat ?? Any suggestions would help. Thanks
Bill from Ohio
Bill from Ohio
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Originally Posted by irish81449
I have a 2001 Mazda 626 4 cyl. auto 73K. Check engine light came on. code showed PO421. "Warm up catalyst efficiency for bank 1 below threshold for engine operating conditions. " Where do I go from here. Autozone suggested changing thermostat, but not a convincing opinion. Should I start there with the thermostat ?? Any suggestions would help. Thanks
Bill from Ohio
Bill from Ohio
It's possible the EGR valve or something related to it has gone bad and set the code. It could be a simple as a bad temperature, pressure or other sensor. Perhaps your O2 sensors are acting up, they have a lot to do with catalytic efficiency. They are a maintainance item and should be replaced periodically.
Christopher