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Home >> Chevrolet >> 2021 >> Trailblazer RS, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Automatic Transmission - VT40 (MRG) - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0641 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
    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 @ T12 Automatic Transmission Assembly
  3. Ignition - On / Vehicle - In Service Mode
  4. Test for 4.8 to 5.2 V between the test points: 5 V Reference circuit terminal 13 @ Component harness & Ground
    • If less than 4.8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 13 @ 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 ohms between the test points: 5 V Reference circuit terminal 13 @ Component harness & 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: K71 Transmission Control Module
    • If greater than 5.2 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: 5 V Reference circuit terminal 13 @ Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K71 Transmission Control Module
    • Go to next step: If between 4.8 and 5.2 V 
  5. Remove the component: Control Valve Body Cover
  6. Connect the electrical connector: X1 @ T12 Automatic Transmission Assembly
  7. Disconnect the electrical connector:
    • B12BA Transmission Fluid Pressure Sensor 1
    • B12BB Transmission Fluid Pressure Sensor 2
  8. Test for 4.8 to 5.2 V between the test points:
    • 5 V Reference circuit terminal 1 @ B12BA Transmission Fluid Pressure Sensor 1 & Ground
    • 5 V Reference circuit terminal 1 @ B12BB Transmission Fluid Pressure Sensor 2 & Ground
    • If not between 4.8 and 5.2 V 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If between 4.8 and 5.2 V 
  9. Test or replace the component:
    • B12BA Transmission Fluid Pressure Sensor 1
    • B12BB Transmission Fluid Pressure Sensor 2
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