Question about Chevrolet TrailBlazer
You don't mention any vehicle specific info, but the codes read as follows:
P0420 - "Catalyst Efficiency Below Threshold (Bank 1)"
P0128 - "Coolant Temp Below Thermostat Regulating Temp"
I'd guess you basic problem is the engine isn't getting hot enough in normal operation.
Try replacing the thermostat. Do be aware that you have to purge the cooling system of any trapped air for proper cooling system function. Some vehicles have 1 or more air bleed screws in the system to aid in this process.
I suspect that if you resolve the P0128 DTC, the other will go away (might have to clear the code and go thru requisite drive cycle.
Posted on Jan 02, 2011
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Posted on Jan 02, 2017
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