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Home >> GMC >> 2021 >> Terrain SLT, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 247 (Automatic Transmission - 6T40 (MNH MNK) Or 6T45 (MHG) - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0851 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2021 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
    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.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector: X1 @ Q8 Control Solenoid Valve Assembly
  3. Ignition - On / Vehicle - In Service Mode
  4. Test for 11 to 13 V between the test points: Signal circuit terminal 3 @ Component harness & Ground
    • If not between 11 and 13 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 3 @ Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 Ω between the test points: Signal circuit terminal 3 @ Component harness & The other end of the circuit
    • If 2 Ω or greater - Repair the open/high resistance in the circuit.
    • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • Go to next step: If between 11 and 13 V 
  5. Ignition/Vehicle - Off
  6. Remove the component: Control Valve Body Cover
  7. Connect the electrical connector: X1 @ Q8 Control Solenoid Valve Assembly
  8. Disconnect the electrical connector: X2 @ Q8 Control Solenoid Valve Assembly - B15 Transmission Internal Mode Switch
  9. Ignition/Vehicle - On
  10. Verify the scan tool parameter: Park/Neutral Position Switch = In Gear
    • If not the specified state 
    1. Test for 11 to 13 V between the test points: Signal circuit terminal 3 & Ground
      • If not between 11 and 13 V - Replace the component: Q8 Control Solenoid Valve Assembly
      • Go to next step: If between 11 and 13 V
    2. Replace the component: K20 Engine Control Module
  11. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal A & Low Reference circuit terminal F
  12. 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 appropriate electrical connector: 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.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 Ω between the test points: Signal circuit terminal 3 @ Q8 Control Solenoid Valve Assembly & The other end of the circuit
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Replace the component: K20 Engine Control Module
    • Go to next step: If the specified state 
  13. Test or replace the component: B15 Transmission Internal Mode Switch
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