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HOMESERVICE MANUALSCHEVROLET2018SONIC LS, 1.8L ENG VIN H, AUTOMATIC TRANSREPAIR AND DIAGNOSISBODY & FRAMEWINDOWSFIXED AND MOVEABLE WINDOW SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESREAR WINDOW DEFOGGER MALFUNCTIONCIRCUIT/SYSTEM TESTING
2018 Chevrolet Sonic LS, 1.8L Eng VIN H, Automatic Trans

Circuit/System Testing

2018 Chevrolet Sonic LS, 1.8L Eng VIN H, Automatic TransSECTION Circuit/System Testing
    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Remove the component: KR5 Rear Defogger Relay
  3. Test for less than 10 ohms between the test points: Ground circuit terminal 85 & Ground
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points: Ground circuit terminal 85 & 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 less than 10 ohms 
  4. Connect a test lamp between the test points: Control circuit terminal 86 & Ground circuit terminal 85
  5. Ignition - On / Vehicle - In Service Mode
  6. Operate the component: Rear Defogger Switch - Pressed

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K33 HVAC Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 86 @ Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    4. Test for less than 2 ohms between the test points: Control circuit terminal 86 @ Relay Socket & Control circuit terminal 16 X2 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K33 HVAC Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K33 HVAC Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 86 @ Relay Socket & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V - Replace the component: K33 HVAC Control Module
    • Go to next step: If the test lamp turns On and Off 
  7. Momentarily connect a 30 A fused jumper wire between the test points: B+ circuit terminal 30 & Control circuit terminal 87

    Verify the component does not turn On and Off when connecting and disconnecting the jumper wire: E18 Rear Defogger Grid

    • If the component turns On and Off 

      Test or replace the component: KR5 Rear Defogger Relay

    • Go to next step: If the component does not turn On and Off 
  8. Ignition/Vehicle & All vehicle systems - Off
  9. Install the component: KR5 Rear Defogger Relay
  10. Disconnect the electrical connector: X1 & X2 @ E18 Rear Defogger Grid
  11. Test for less than 10 ohms between the test points: Ground circuit terminal 1 X2 & Ground
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points: Ground circuit terminal 1 X2 @ Component harness & 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 less than 10 ohms 
  12. Connect a test lamp between the test points: Control circuit terminal 1 X1 & Ground circuit terminal 1 X2
  13. Ignition - On / Vehicle - In Service Mode
  14. Operate the component: Rear Defogger Switch - Pressed

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 

      Repair the open/high resistance in the circuit: Control Circuit

    • If the test lamp is always On 

      Repair the short to voltage on the circuit: Control Circuit

    • Go to next step: If the test lamp turns On and Off 
  15. Test or replace the component: E18 Rear Defogger Grid
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.