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Home >> Cadillac >> 2019 >> CTS Base, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 68 (Automatic Transmission - 8L45 (M5N) Or 8L90 (M5U) - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0658, P0659, P2670, or P2671 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2018 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
  2. Disconnect the electrical connector: X175@T12 Automatic Transmission Assembly
  3. Connect a test lamp between the test points:
    • { P0658, P0659 } Control circuit terminal 18 & Ground
    • { P2670, P2671 } Control circuit terminal 19 & Ground
  4. Ignition - On / Vehicle - In Service Mode
  5. Perform the scan tool control function:
    • { P0658, P0659 } High Side Driver 1 - On and Off
    • { P2670, P2671 } High Side Driver 2 - On and Off
    • Verify the test lamp turns On and Off.
    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points:
      • { P0658, P0659 } Control circuit terminal 18 & Ground
      • { P2670, P2671 } Control circuit terminal 19 & 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:
      • { P0658, P0659 } Control circuit terminal 18 @Component harness & Terminal 33@Control module harness
      • { P2670, P2671 } Control circuit terminal 19 @Component harness & Terminal 49@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 the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    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:
      • { P0658, P0659 } Control circuit terminal 18 @Component harness & Ground
      • { P2670, P2671 } Control circuit terminal 19 @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 the test lamp turns On and Off 
  6. Ignition/Vehicle - Off
  7. Connect the electrical connector: X175@T12 Automatic Transmission Assembly
  8. Remove the component: Automatic Transmission Fluid Pan
  9. Ignition - On / Vehicle - In Service Mode
  10. Disconnect the electrical connector: Q77 Transmission Control Solenoid Valve
  11. Verify the scan tool parameter:
    • High Side Driver 1, 2 Circuit High Voltage Test Status = OK or Not Run
    • High Side Driver 1, 2 Circuit Low Voltage Test Status = OK or Not Run
    • High Side Driver 1, 2 Circuit Open Test Status = OK or Not Run
    • If not the specified state and there are components connected to the circuit 

      Disconnect a component and repeat step 10.

    • If not the specified state with all components disconnected from the circuit 

      Replace the component: Automatic Transmission Wiring Harness

    • Go to next step: If the specified state 
  12. Test or replace the component: The component that was disconnected last.
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