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Home >> GMC >> 2018 >> Terrain SL >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Headlights >> Lighting System - Diagnostic Information And Procedures >> Diagnostic Information And Procedures >> DTC B3410 Or B3420: Headlamp Leveling Control Module Front/Rear Axle Sensor Signal Circuit >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate B51 Suspension Height Sensor, ignition ON.
  2. Verify a test lamp illuminates between the low reference circuit terminal 2 and B+.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K26 Headlamp Control Module.
    • Go to next step: If the test lamp illuminates 
  3. Ignition ON.
  4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 1 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for infinite resistance between the 5 V reference 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 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K26 Headlamp Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K26 Headlamp Control Module.
    • Go to next step: If between 4.8 - 5.2 V 
  5. Verify the appropriate scan tool Leveling Position Sensor Signal parameter is less than 1 mm.
    • If 1 mm or greater 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 3 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K26 Headlamp Control Module.
    • Go to next step: If less than 1 mm 
  6. Ignition OFF.
  7. Connect the red lead of the J-38522  Variable Signal Generator to the signal circuit terminal 3 and the black lead of the J-38522  Variable Signal Generator to the low reference circuit terminal 2.
  8. Adjust the J-38522  Variable Signal Generator to the settings listed below:
    • Signal control to 5 V
    • Frequency control to 250 Hz
    • Duty cycle control to the 60%
  9. Ignition ON, verify the appropriate scan tool Leveling Position Sensor parameter is 11 mm.
    • If not 11 mm 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for infinite resistance between the signal 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 signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K26 Headlamp Control Module.
    • Go to next step: If 11 mm 
  10. Test or replace the B51 Suspension Height Sensor.
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