Insufficient Heating Performance Due to Exhaust Manifold Outlet Pipe

Some 2020-2021 Encore GX and Trailblazer models equipped with the 1.3L turbo engine (RPO L3T) may have insufficient heat or no heat in the cabin after driving for several minutes.

During diagnosis, GDS 2 Engine Cooling and HVAC Data may show that the temperature difference between the heater inlet (ECT sensor 3) and heater outlet (ECT sensor 4) is over 30°C (86°F) when the engine is warmed fully. If this temperature difference between the heater inlet (ECT sensor 3) and heater outlet (ECT sensor 4) is found, use a general boroscope to check for a blocked exhaust manifold outlet pipe. (Fig. 9) Allow enough time for the engine cooling system to cool before opening.

 

Fig. 9

 

An internal blockage of the exhaust manifold outlet pipe may result in insufficient heating performance. If the pipe is blocked, replace the pipe. (Fig. 10) Refer to Exhaust Manifold Outlet Pipe Replacement in the appropriate Service Information.

 

Fig. 10

 

After the new exhaust manifold outlet pipe is installed, run the engine to raise the engine coolant temperature and check the GDS 2 Engine Cooing and HVAC Data menu. The temperature of the heater inlet (ECT sensor 3) and heater outlet (ECT sensor 4) should be similar.

For additional information and part numbers, refer to Bulletin #21-NA-223.

 

– Thanks to Frank Jakubiec

Engine Wiring Harness Chafing Repairs
HVAC Temperature Actuator Operation at Low Temperatures

2 Comments

  1. The Exhaust Manifold Outlet Pipe is the coolant pipe connected to the outlet side of the Integrated Exhaust Manifold, as such it’s named the Exhaust Manifold Outlet Pipe Assembly.

  2. Brian Hooser says:

    Why is this heater pipe called “Exhaust Manifold Outlet Pipe”? An exhaust manifold has historically been used to allow combustion gasses to be directed out of the combustion chamber.

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