SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2018TAHOE FL, 4WD, GASREPAIR AND DIAGNOSISBODY & FRAMEWINDOWSFIXED AND MOVEABLE WINDOW SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESREAR WINDOW DEFOGGER MALFUNCTIONCIRCUIT/SYSTEM TESTING
2018 Chevrolet Tahoe FL, 4WD, Gas

Circuit/System Testing

2018 Chevrolet Tahoe FL, 4WD, GasSECTION 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 60 & Ground
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points:Ground circuit terminal 60 & 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 65 & Ground circuit terminal 60
  5. Ignition - On / Vehicle - In Service Mode
  6. Perform the scan tool control function:Rear Defogger - On and Off

    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 65 @Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance
    4. Test for less than 2 ohms between the test points:Control circuit terminal 65 @Relay Socket & Terminal 19 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 65 @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. Verify a test lamp turns On between the test points:B+ circuit terminal 30 & 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:B+ circuit terminal 30 @Relay Socket & Output terminal@ F24RA Fuse
      • 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:B+ circuit terminal 30 & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance
    3. Remove the component: F24RAFuse
    4. Test for infinite resistance between the test points:Control circuit terminal 62 @Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Test or replace the component:KR5 Rear Defogger Relay
    • Go to next step: If the test lamp turns On 
  8. Momentarily connect a 30 A fused jumper wire between the test points:B+ circuit terminal 30 & Control circuit terminal 62

    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 
  9. Ignition/Vehicle & All vehicle systems - Off
  10. Install the component:KR5 Rear Defogger Relay
  11. Disconnect the electrical connector:X1 & X2 @E18 Rear Defogger Grid
  12. Test for less than 10 ohms between the test points:Ground circuit terminal 1 X1 & 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 X1 @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 
  13. Connect a test lamp between the test points:Ground circuit terminal 1 X2 & Ground circuit terminal 1 X1
  14. Ignition - On / Vehicle - In Service Mode
  15. Perform the scan tool control function:Rear Defogger - On and Off

    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 
  16. Test or replace the component:E18 Rear Defogger Grid
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.