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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 89 (Driver Assistance Systems) >> Diagnostic Information and Procedures >> Forward Collision Alert System Malfunction >> 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.

Test 1

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector:S155 Lane Departure Warning Switch
  3. Verify a test lamp turns On between the test points:Ground circuit terminal 8 & B+
    • If the test lamp does not turn On 
    1. Test for less than 2 ohms between the test points:Ground circuit terminal 8 & Ground Connection
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • Go to next step: If the test lamp turns On 
  4. Connect the electrical connector:S155 Lane Departure Warning Switch
  5. Disconnect the electrical connector:B174W Frontview Camera - Windshield
  6. Test for less than infinite resistance between the test points: Signal circuit terminal 10 & Ground.
    • If infinite resistance 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector:S155 Lane Departure Warning Switch
    3. Test for less than 2 ohms between the test points:Signal circuit terminal 4@Component harness & Signal circuit terminal 10@Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component:S155 Lane Departure Warning Switch
    • Go to next step: If less than infinite resistance 
  7. Connect a DMM between the test points:Signal circuit terminal 10 & Ground
  8. Press and release the switch:Lane Departure Warning Switch

    Verify resistance on the DMM changes when pressing and releasing the switch.

    • If resistance does not change 
    1. Disconnect the electrical connector:S155 Lane Departure Warning Switch
    2. Test for less than 1 V between the test points:Signal circuit terminal 4@Component harness & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Test for infinite resistance between the test points:Signal circuit terminal 4@Component harness & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If less than 2 ohms - Replace the component:S155 Lane Departure Warning Switch
    • Go to next step: If resistance changes 
  9. Test or replace the component:B174W Frontview Camera - Windshield

Test 2

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Disconnect the electrical connector:P43 Collision Alert Indicators
  3. Verify a test lamp turns On between the test points:Ground circuit terminal 4 & B+
    • If the test lamp does not turn On 
    1. Test for less than 2 ohms between the test points:Ground circuit terminal 4 & Ground terminal
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • Go to next step: If the test lamp turns On 
  4. Ignition - On / Vehicle - In Service Mode
  5. Verify a test lamp turns On between the test points:Ignition circuit terminal 1 & 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 ohms between the test points:Ignition circuit terminal 1@P43 Collision Alert Indicators & The other end of the circuit
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - 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 & Remove - Test lamp
    2. Test for infinite resistance between the test points:Ignition circuit terminal 1 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Test or replace the component:P43 Collision Alert Indicators
    • Go to next step: If the test lamp turns On 
  6. Ignition/Vehicle - Off
  7. Disconnect the electrical connector:P16 Instrument Cluster
  8. Ignition - On / Vehicle - In Service Mode
  9. Test for less than 1 V between the test points:
    • Control circuit terminal 8@P16 Instrument Cluster & Ground
    • Control circuit terminal 6@P16 Instrument Cluster & Ground
    • If 1 V or greater 

      Repair the short to voltage on the circuit.

    • Go to next step: If less than 1 V 
  10. Ignition/Vehicle - Off
  11. Test for infinite resistance between the test points:
    • Control circuit terminal 8@P16 Instrument Cluster & Ground
    • Control circuit terminal 6@P16 Instrument Cluster & Ground
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
  12. Test for less than 2 ohms between the test points:
    • Control circuit terminal 8@P16 Instrument Cluster & Control circuit terminal 3@P43 Collision Alert Indicators
    • Control circuit terminal 6@P16 Instrument Cluster & Control circuit terminal 2@P43 Collision Alert Indicators
    • If 2 ohms or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 
  13. Replace the component:P43 Collision Alert Indicators
  14. Ignition - On / Vehicle - In Service Mode
  15. Perform the appropriate scan tool control function:All Indicators

    Verify the component activates:Collision Alert - Indicators

    • If the component does not work as specified 

      Replace the component:P16 Instrument Cluster

    • Go to next step: If the component works as specified 
  16. All OK.
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