Circuit/System Testing

Rear Window Defogger System Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the X3 harness connector at the S34 HVAC Controls Switch Assembly. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal C 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 A and ground.
   • If the test lamp does not illuminate and the circuit fuse is good 
   1. Ignition OFF.
   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.
   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 S34 HVAC Controls Switch Assembly.
   • If the test lamp illuminates 
5. Verify a test lamp illuminates between the ignition circuit terminal B and ground.
   • If the test lamp does not illuminate and the circuit fuse is good 
   1. Ignition OFF.
   2. Test for less than 2 Ω in the ignition 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.
   2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the S34 HVAC Controls Switch Assembly.
   • If the test lamp illuminates 
6. Ignition OFF and all vehicle systems OFF, connect the X3 harness connector at the S34 HVAC Controls Switch Assembly and disconnect the KR5 Rear Defogger Relay. It may take up to 2 minutes for all vehicle systems to power down.
7. Test for less than 10 Ω between the ground circuit terminal 85 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 
8. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85, Ignition ON.
9. Verify the test lamp turns ON and OFF when pressing the rear window defogger switch.
   • If the test lamp is always OFF 
   1. Ignition OFF, remove the test lamp, disconnect the X3 harness connector at the S34 HVAC Controls Switch Assembly.
   2. Test for infinite resistance between the control 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 control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S34 HVAC Controls Switch Assembly.
   • If the test lamp is always ON 
   1. Ignition OFF, disconnect the X3 harness connector at the S34 HVAC Controls Switch Assembly, Ignition ON.
   2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S34 HVAC Controls Switch Assembly.
   • If the test lamp turns ON and OFF 
10. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
11. Verify both E18L Rear Defogger Grid-Left and E18R Rear Defogger Grid-Right are activated.
    • If both E18L Rear Defogger Grid-Left and E18R Rear Defogger Grid-Right are not activate 
    1. Ignition OFF, remove the 10 A fused jumper wire, disconnect the harness connectors at the E18L Rear Defogger Grid-Left and E18R Rear Defogger Grid-Right.
    2. Test for infinite resistance between the control circuit and ground.
       • If less than infinite resistance, repair the short to ground on the circuit.
       • If infinite resistance, replace the E18L Rear Defogger Grid-Left and E18R Rear Defogger Grid-Right.
    • If both E18L Rear Defogger Grid-Left and E18R Rear Defogger Grid-Right are activated 
12. Test or replace the KR5 Rear Defogger Relay.

Single Defogger Grid Malfunction

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate E18 Rear Defogger Grid. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal listed below and ground.
   • E18L Rear Defogger Grid-Left - ground circuit terminal A X2 (A12)
   • E18L Rear Defogger Grid-Left - ground circuit terminal B (A18)
   • E18R Rear Defogger Grid-Right - ground circuit terminal A X2 (A12)
   • E18R Rear Defogger Grid-Right - ground circuit terminal B (A18)
   • 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. Connect the harness connector at the E18 Rear Defogger Grid and disconnect the KR5 Rear Defogger Relay.
5. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
   • If the test lamp illuminates 

     Repair the short to voltage on the control circuit

   • If the test lamp does not illuminate 
6. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
7. Verify the E18 Rear Defogger Grid is activated.
   • If the E18 Rear Defogger Grid does not activate 
   1. Ignition OFF, remove the 10 A fused jumper wire, disconnect the harness connector at the E18 Rear Defogger Grid.
   2. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the E18 Rear Defogger Grid.
   • If the E18 Rear Defogger Grid activates 
8. Test or replace the KR5 Rear Defogger Relay.