'07 TrailBlazer SS P2A01, P2A04, and P0420 codes
#1
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P2A01 - O2 Sensor Circuit Range/Performance Bank 1 Sensor 2
P2A04 - O2 Sensor Circuit Range/Performance Bank 2 Sensor 2
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
Replace both downstream/post cat/rear O2 sensors, and see if the code goes away?
P2A04 - O2 Sensor Circuit Range/Performance Bank 2 Sensor 2
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
Replace both downstream/post cat/rear O2 sensors, and see if the code goes away?