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Home >> Cadillac >> 2021 >> CT5 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 6 (Engine Controls And Fuel - 3.0L (LGY) - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> DTC P135A or P135B >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle - Off
  2. Disconnect the appropriate electrical connector: K20 Engine Control Module
  3. Connect a 3 A fused jumper wire between the test points: Control circuit terminal 9 X1 & Ground
  4. Ignition - On / Vehicle - In Service Mode
  5. Verify a test lamp turns On between the test points:
    • { P135A } Ignition circuit terminal 32 X1 & Ground
    • { P135B } Ignition circuit terminal 44 X4 & Ground
    • If the test lamp does not turn On and the circuit fuse is OK 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Test for less than 2 Ω between the test points: Ignition circuit terminal 32/44 @ Control module harness & Output terminal @ Fuse
      • If 2 Ω or greater - Repair the open/high resistance in the circuit.
      • If less than 2 Ω - Verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not turn On and the circuit fuse is open 
    1. Ignition/Vehicle - Off
    2. Replace the component: Fuse
    3. Ignition - On / Vehicle - In Service Mode
    4. Verify the fuse does not open.
      • If the fuse opens and there are components connected to the circuit - Disconnect a component and repeat procedure starting at step 5.1
      • If the fuse opens with all components disconnected from the circuit - Repair the short to ground on the circuit.
      • If the fuse does not open after disconnecting a component from the circuit - Replace the component disconnected last.
      • Go to next step: If the fuse does not open with all components connected, except the following component: K20 Engine Control Module
    5. Ignition/Vehicle - Off
    6. Connect the electrical connector: K20 Engine Control Module
    7. Replace the component: Fuse
    8. Ignition - On / Vehicle - In Service Mode
    9. Verify the fuse does not open.
      • If the fuse is open - Replace the component: K20 Engine Control Module
      • Go to next step: If the fuse does not open.
    10. Verify the fuse does not open when any of the components are activated.
      • If the fuse opens - Replace the component that caused the fuse to open when activated.
      • Go to next step: If the fuse does not open.
    11. All OK.
    • Go to next step: If the test lamp turns On 
  6. Replace the component: K20 Engine Control Module
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