Rough Running Engine in Extreme Cold Temperatures

A 2020 Silverado HD or Sierra HD equipped with the 6.6L V8 engine (RPO L8T) may have a rough idle or reduced engine power in very cold climates (-10°F or -23°C). The Check Engine lamp may be illuminated along with DTCs P0123 (Throttle Position Sensor 1 Circuit High Voltage) and P0222 (Throttle Position Sensor 2 Circuit Low Voltage) set. These engine performance conditions may be caused by an internal circuit fault within the throttle body.

If these conditions are found on a vehicle exposed to extreme cold, replace the throttle body assembly following the service procedure in the appropriate Service Information. (Fig. 10) In addition, add a ground wire using two 8 mm ring terminals and one 8-inch piece of 14-gauge wire.


Fig. 10


To install the ground wire, remove the oil cap and engine cover from the rocker cover on the left bank of the engine. Attach one end of the ground wire to the lower-right throttle body fastener with the crimp side of the ring terminal facing the bolt head. (Fig. 11)


Fig. 11


Attach the other end to the rocker cover fastener with the crimp side of the ring terminal facing the bolt head. (Fig. 12)


Fig. 12


Once the ground wire is installed and secure (Fig. 13), clear any DTCs and road test the vehicle to verify the repair.


Fig. 13


Refer to #PIP5706 for additional information.


– Thanks to Tim Lightfoot

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