Circuit/System Verification

Engine running.
Verify the scan tool Rear Defrost Switch parameter changes between Inactive and Active when pressing the rear window defogger switch.
- If the parameter does not change between On and Off
  Replace the K33 HVAC Control Module.
- If the parameter changes between On and Off
Verify the E18 Rear Defogger Grid turns ON and OFF when commanding the Rear Defog Request On and Off with a scan tool.
- If the E18 Rear Defogger Grid does not turn ON and OFF
  Refer to Circuit/System Testing
- If the E18 Rear Defogger Grid turns ON and OFF
Verify the rear window defogger indicator turns ON and OFF when pressing the rear window defogger switch.
- If the indicator does not turn ON and OFF
  Replace the K33 HVAC Control Module.
- If the indicator turns ON and OFF
All OK.