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Home >> Cadillac >> 2017 >> CTS Base, AWD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Wiper/Washer Systems >> Wiper System And Washer System >> Diagnostic Information and Procedures >> DTC B370A: Rain Sensor >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, all vehicle systems OFF, disconnect the harness connector at the B177 Rain/Ambient Light Sensor Module. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 3 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.
  4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF, remove the test lamp.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, remove the test lamp.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the B177 Rain/Ambient Light Sensor Module.
    • If the test lamp illuminates 
  5. Test for 5.0-10.0 V between the serial data circuit terminal 2 and ground.
    • If less than 5.0 V 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module and the harness connector at the M79 Windshield Wiper Motor Module.
    2. Test for infinite resistance between the serial data circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the serial data circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If greater than 10.0 V 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the serial data circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If between 5.0-10.0 V 
  6. Test or replace the B177 Rain/Ambient Light Sensor Module.
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