Circuit/System Verification

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Ignition - On / Vehicle - In Service Mode & Engine - Off
Verify DTC P0502, P0503, P0721, P0722, P0723, P077C, P077D, P2160 or P2161 is not set.
- If any of the DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle
- Go to next step: If none of the DTCs are set
Ignition On - Engine Running - Greater than 1 min
Ignition OFF for greater than 2?min, key out of the ignition/keyless start transmitter 1 m (3 ft) away from the vehicle, and all vehicle systems OFF.
Ignition ON/Vehicle in Service Mode
Verify DTC P17D4, P185F, P279A, P279B, P279C is only set as a history DTC.
- If any of the DTCs are set Refer to Circuit/System Testing
- If any of the DTCs are set as history Refer to Diagnostic Aids before proceeding with Circuit/System Testing.
- Go to next step: If none of the DTCs are set
Clear All Vehicle DTCs
Drive the vehicle at a speed greater than 10?km/h (6?mph) and verify the following parameters match the actual vehicle speed and each other. Both parameters should show a smooth/steady curve when viewed in graph form:
- Transmission OSS scan too parameter in the Transmission Control Module scan tool data list
- Transfer Case OSS scan too parameter in the Engine Control Module scan tool data list
- If the above parameters do not match or are not smooth
  A fault exists with the B14S Transmission Output Shaft Speed Sensor or the B115 Vehicle Speed Sensor. Refer to Diagnostic Trouble Code (DTC) List - Vehicle
- If the above parameters match and are smooth
All OK.