Pinpoint Test R: Park Does Not Engage

• Gear Shift Module (GSM) 
  • If any diagnostic trouble codes (DTCs) are present in the GSM, resolve those first.
  • Using a diagnostic scan tool, access the GSM and monitor PID GEAR_CMD. Move the selector lever through all gear positions and make sure PID GEAR_CMD matches each selector lever position. If PID GEAR_CMD does not change with the position of the selector lever, INSTALL a new GSM. REFER to: Gear Shift Module (GSM) - Vehicles With: Column Shift .

• Park is manually released 
  • Verify park is not manually released. REFER to: Transmission Park by Wire Manual Release .

• Internal transmission components 
  • Once out of park, the shift-by-wire variant of the 10R transmission uses hydraulic pressure from the A, B, C, D or F clutches to hold the system out of park. If any other observable symptoms indicate one of those clutches is stuck on, RESOLVE those symptoms first. REFER to: Diagnosis By Symptom .
  • Check the park lock pawl solenoid pin for being stuck extended. REFER to: Park Lock Pawl Solenoid .
  • Inspect the park pawl, park pawl actuator rod, TR sensor and park return spring for damage or binding. Make sure all park components are properly installed and connected. REPAIR or INSTALL new components as necessary. REFER to: Transmission .
  • Remove and inspect the park lock pawl valve. If the valve or bore is damaged, INSTALL a new main control valve body. REFER to: Main Control Valve Body .
  • Disassemble the main control valve body and inspect the park lock pawl valve hydraulic circuits for damage, leaks or blockage. CLEAN or INSTALL new components as necessary. REFER to: Main Control Valve Body .

Possible Sources 

• GSM fault
• Park is manually released
• Internal transmission park components
• Clutch fault

Diagnostic steps are not provided for this symptom or DTC. REFER to: Diagnostic Methods