Circuit/System Testing

Single Outside Mirror Defogger Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate A9 Outside Rearview Mirror. 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 5 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. Engine running, connect a test lamp between the control circuit terminal 4 and the ground circuit terminal 5.
4. Verify the test lamp turns ON when commanding the Rear Defogger On with a scan tool.
   • If the test lamp is always OFF 
   1. Ignition OFF, remove the test lamp, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
   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 X50A Fuse Block - Underhood.
   • If the test lamp turns ON  
5. Test or replace the E17 Outside Rearview Mirror Glass.

Both Outside Mirror Defogger Malfunction

1. Ignition OFF, disconnect the harness connector at the appropriate A9 Outside Rearview Mirror. Engine running
2. Connect a test lamp between the control circuit terminal 4 and ground.
3. Verify the test lamp turns ON and OFF when commanding the Rear Defogger On and Off with a scan tool.
   • If the lamp is always ON 
   1. Ignition OFF, remove the test lamp, disconnect the X2 harness connector at X50A Fuse Block - Underhood, 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, refer to Rear Window Defogger Malfunction .
   • If the lamp is always OFF 
   1. Ignition OFF, remove the test lamp, disconnect the X2 harness connector at X50A Fuse Block - Underhood, ignition ON.
   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, refer to Rear Window Defogger Malfunction
   • If the lamp turns on and off 
4. Replace the E17 Outside Rearview Mirror Glass.