My 2004 S10 Blazer is throwing these codes. Which I don't know what these are. Any ideas guys??

PO128 Coolant Thermostat ( Coolant Temperature Below Thermostat Regulating Temperature)

PO155 O2 Sensor Heater Circuit Malfunction ( Bank 2 Sensor 1 )

PO446 Evaporative Emission Control System Vent Control Circuit Malfunction

Please Help.

 

They can all be found in this section:
Diagnostic Trouble Codes (DTCs)

 

If that's the exact order that the DTC's were retrieved, check the coolant level and coolant temperature after the engine has been running for 15 or 20 minutes. Check it with an infra red thermometer at the thermostat housing and check the ECT voltage on a capable scan tool. They should both be approximately 195F. If both temp readings are low, replace the thermostat. Then clear the DTC's and perform a drive cycle. If any DTC's return, troubleshoot them in the order they are retrieved. http://www.obdii.com/drivecycle.html

 

How the hell can it throw these codes, and the repair garage says it's the O2 Sensor? They fixed the problem so they say. This is a family members vehicle that I was trying to help them fix. The codes it threw were totally unrelated to the O2 Sensor to my knowledge.

 

DTC's must be diagnosed and repaired in the order that they are retrieved. After the repair, perform a drive cycle to confirm the repair. Whenever there is more than one DTC, any subsequent DTC's can be caused by the first one.

P0128 is low coolant temperature: If the engine takes an excessive amount of time to reach operating temperature, it's possible that oxygen sensor DTC's could be set. They depend on heat to operate correctly, which is one of the reasons they have heaters in them. Not quite sure how an oxygen sensor could affect coolant temperature Might want to ask them, I'd be curious to hear the explanation!

The P0155 indicates a problem with the heater circuit in the oxygen sensor closest to the right exhaust manifold. This DTC may or may not be related to the P0128. Circuits would need to be checked to diagnose the problem, only if it shows up after repairing the P0128.