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Home >> GMC >> 2018 >> Terrain Denali, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (Automatic Transmission - 6T40 (MNH MNK) Or 6T45 (MHG) - Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P0850, P0851, Or P0852: Park/Neutral Position Switch Circuit >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
    NOTE:

    Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Remove the component:Control Valve Body Cover
  3. Connect the electrical connector:Q8 Control Solenoid Valve Assembly
  4. Disconnect the electrical connector:B15 Transmission Internal Mode Switch
    5. NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  5. Test for less than 10 ohms between the test points:Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly & Ground
    • If 10 ohms or greater 

      Replace the component:Q8 Control Solenoid Valve Assembly

    • Go to next step: If less than 10 ohms 
  6. Verify the scan tool parameter:Internal Mode Switch A/B/C/P=High High High High
    • If not the specified state 

      Replace the component:Q8 Control Solenoid Valve Assembly

    • Go to next step: If the specified state 
  7. Connect a 3 A fused jumper wire between each of the following circuit pairs, one at a time:
    • Signal circuit terminal B & Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly
    • Signal circuit terminal C & Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly
    • Signal circuit terminal D & Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly
    • Signal circuit terminal E & Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly

      Verify the scan tool parameter:Internal Mode Switch A/B/C/P=3 High and 1 Low

    • If not the specified state 

      Replace the component:Q8 Control Solenoid Valve Assembly

    • Go to next step: If the specified state 
  8. Verify the scan tool parameter:Park/Neutral Position Switch =In Gear
    • If not the specified state 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the electrical connector: X1 @K20 Engine Control Module
    3. Test for infinite resistance between the test points:Signal circuit terminal A @Q8 Control Solenoid Valve Assembly & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component:K20 Engine Control Module
    • Go to next step: If the specified state 
  9. Connect a 3 A fused jumper wire between the test points:Signal circuit terminal A & Low Reference circuit terminal F @Q8 Control Solenoid Valve Assembly
  10. Verify the scan tool parameter:Park/Neutral Position Switch=Park/Neutral
    • If not the specified state 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector: X1@K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points:Signal circuit terminal A @Q8 Control Solenoid Valve Assembly & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points:Signal circuit terminal A @Q8 Control Solenoid Valve Assembly & The other end of the circuit @Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component:K20 Engine Control Module
    • Go to next step: If the specified state 
  11. Test or replace the component:B15 Transmission Internal Mode Switch
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