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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 57 (Automatic Transmission - 8L90 (M5U) - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P182A, P1838, P18B5, P18BA, or P18BF >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition/Vehicle - Off
    2. 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.

  3. Disconnect the electrical connector: x175 @ T12 Automatic Transmission Assembly
  4. Test for 8. 3 to 9. 3 V between the test points: 9 V Reference terminal 29 @ X175
    • If less than 8. 3 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: 9 V Reference terminal 29 @ X175 & 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 1 ohms between the test points: 9 V Reference terminal 29 @ X175 & The other end of the circuit
      • If 1 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 1 ohms - Replace the component: K71 Transmission Control Module
    • If greater than 9. 3 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K71 Transmission Control Module
    3. Ignition/Vehicle - On
    4. Test for less than 1 V between the test points: 9 V Reference terminal 29 @ X175 & 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 8. 3 and 9. 3 V 
  5. Ignition/Vehicle - Off
  6. Connect a 3 A fused jumper wire between the test points: 9 V Reference terminal 29 & Signal circuit terminal 22 @ X175
  7. Ignition/Vehicle - On
  8. Verify the scan tool parameter: Internal Mode Switch A = 4. 8-5. 2
    • If greater than 5. 2 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K71 Transmission Control Module
    3. Ignition/Vehicle - On
    4. Test for less than 1 V between the test points: Signal circuit terminal 22 @ X175 & 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
    • If less than 4. 8 V 
    1. Ignition/Vehicle - Off
    2. Disconnect the appropriate electrical connector: K71 Transmission Control Module
    3. Test for infinite resistance between the test points: Signal circuit terminal 22 @ X175 & 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 1 ohms between the test points: Signal circuit terminal 22 @ X175 & The other end of the circuit
      • If 1 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 1 ohms - Replace the component: K71 Transmission Control Module
    5. Test for infinite resistance between the test points: Signal circuit terminal 22 &
      • Signal circuit terminal 21 @ X175
      • Signal circuit terminal 23 @ X175
      • Signal circuit terminal 24 @ X175
      • Signal circuit terminal 28 @ X175
      • Signal circuit terminal 34 @ X175
      • If less than infinite resistance - Repair the short between the circuits.
      • If infinite resistance - Replace the component: K71 Transmission Control Module
    • Go to next step: If between 4. 8 and 5. 2 V 
  9. Test or replace the component: B15 Transmission Internal Mode Switch
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