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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 226 (Driver Assistance Systems - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC B1270 or B1271 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE:

    Make sure to use a high impedance test lamp like special tool EL-35616-210.

  1. Ignition OFF and all vehicle systems OFF, disconnect the in-line harness connector for the appropriate A9 Outside Rearview Mirror. It may take up to 2 min for all vehicle systems to power down.
    • Driver Door Harness to Outside Rearview Mirror
    • Passenger Door Harness to Outside Rearview Mirror
  2. Test for less than 10 Ω between the ground circuit terminal 5 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Ignition ON, connect a test lamp between the control circuit terminal 15 and the ground circuit terminal 5.
  4. Verify the test lamp turns ON and OFF when commanding the Object Detection Alert Indicators On and Off with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the harness connector at the appropriate S79 Front Side Door Window Control Switch.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79 Front Side Door Window Control Switch.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the harness connector at the S79 Front Side Door Window Control Switch, ignition ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79 Front Side Door Window Control Switch.
    • Go to next step: If the test lamp turns ON and OFF 
  5. Test or replace the A9 Outside Rearview Mirror Glass.
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