Aura L4-2.4L (2008)
Control Module References (See: Testing and Inspection/Programming and Relearning)for Scan Tool Information
Circuit/System Verification
1. Ignition ON, observe the scan tool Manual HVAC Rear Defog Sw parameter while pressing the Defog Switch. The reading should change
between ON and OFF.
‹› If the reading does not change between the commanded states, refer to HVAC Control Module Malfunction.
2. Command the rear window defogger ON and OFF with the scan tool. The rear window defogger and Defog Indicator should turn ON and OFF
when changing between the commanded states.
‹› If the rear window defogger does not turn ON and OFF when changing between the commanded states, refer to Rear Defogger Malfunction.
‹› If the Defog Indicator does not illuminate or continuously illuminates, refer to Rear Defogger Indicator Malfunction.
Circuit/System Testing
HVAC Control Module Malfunction
1. Ignition OFF, disconnect the harness connector C1 at the HVAC control module.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal B5 and ground.
‹› If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Manual HVAC Rear Defog Sw parameter is OFF.
‹› If not the specified value, test the signal circuit terminal A8 for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3-amp fused jumper wire between the signal circuit terminal A8 and ground. Verify the scan tool Manual HVAC Rear Defog Sw
parameter is ON.
‹› If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the HVAC control module.
Rear Defog Indicator Malfunction
1. Ignition OFF, disconnect the harness connector C1 at the HVAC control module.
2. Disconnect the R/WDO DEFOG relay.
3. Connect a test lamp between the control circuit terminal B8 and ground.
4. Ignition ON, command the Rear Defog Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the
commanded states.
‹› If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
‹› If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the
BCM.
5. If all circuits test normal, test or replace the HVAC control module.
Rear Defogger Malfunction
1. Ignition OFF, disconnect the R/WDO DEFOG relay.
2. Ignition OFF, test for less than 1 ohm of resistance between the relay coil ground circuit and ground.
‹› If greater than the specified range, test the relay coil ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit and ground.
‹› If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.
4. Verify that a test lamp illuminates between the relay switch side B+ circuit and ground.
‹› If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal
and the fuse is open, test the relay controlled output circuit for a short to ground.
5. Ignition OFF, disconnect the harness connector at the rear window defogger grid.
6. Ignition OFF, test for less than 1 ohm of resistance between the rear window defogger grid ground circuit terminal A and ground
