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• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Outside Wing Mirror Heater Relay B+ | 2 | 2 | -- | -- |
Rear Demist Relay B+ | 1 | 1 | -- | -- |
Outside Wing Mirror Heater Relay Control | B0283 02 | 2 | B0283 05 | -- |
Rear Demist Relay Control | B0283 02 | 1 | B0283 05 | -- |
Upper Rear Demister Grid Control | 2 | 2 | 2 | -- |
Lower Rear Demister Grid Control | 1 | 1 | 1 | -- |
Lower Rear Window Demister Grid Ground | -- | 2 | -- | -- |
Upper Rear Window Demister Grid Ground | -- | 1 | -- | -- |
Outside Wing Mirror Heater Relay Ground | -- | 2 | -- | -- |
Rear Demist Relay Ground | -- | 1 | -- | -- |
1. Upper Rear Demister Grid Malfunction 2. Lower Rear Demister Grid Malfunction |
When the HVAC control module receives a rear window demist request from the HVAC control faceplate, the HVAC control module will supply voltage to the relay coil. Battery positive voltage is supplied at all times to the relay switched input and the relay coil is always grounded. This allows battery positive voltage from the relay switched input to flow through the switch contacts and out the relay switched output to the rear window demister grid.
Rear window demister indicator will still function when the switch is pressed but any of the following conditions may cause the rear window demister not to function:
• | Ambient temperature at the HVAC control module must be less than 10°C (50°F). |
• | System voltage is out of range. |
• | A DTC is set that disables rear window demister functionality. |
Rear Window Demister Description and Operation
Control Module References for scan tool information
⇒ | If the value does not change, replace the A20 radio/HVAC control. |
⇒ | If the demister indicator is always ON or always OFF, replace the A20 radio/HVAC control. |
⇒ | If a single rear window demister grid does not turn ON and OFF when changing between the commanded states, refer to Single Rear Window Demist Grid Malfunction. |
⇒ | If both rear window demister grids do not turn ON and OFF when changing between the commanded states, refer to Rear Window Demister Malfunction. |
• | Terminal A E18B rear demister grid-lower. |
• | Terminal 1 E18A rear demister grid-upper |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
• | Terminal 40 KR5 rear demister relay. |
• | Terminal 86 KR4B outside wing mirror heater relay. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
• | B+ terminal 43 and control terminal 42 KR5 rear demister relay. |
• | B+ terminal 30 and control terminal 87 KR4B outside wing mirror heater relay. |
⇒ | If the rear demister grid does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the E18 rear window demister grid. |
⇒ | If the rear demister grid does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the E18 rear window demister grid. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC control module. |
⇒ | 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 K33 HVAC control module. |
⇒ | If the E18B rear demister grid-lower does not turn ON, test or replace the KR4B outside wing mirror heater relay. |
⇒ | If the test lamp remains bright at the middle of the grid line, test for an open between the test point and the ground side of the grid. |
⇒ | If the test lamp remains off at the middle of the grid line, test for an open between the test point and the voltage supply side of the grid |
⇒ | If the not within the specified range, replace the relay. |
• | 3 and 2 |
• | 3 and 5 |
• | 3 and 1 |
• | 1 and 5 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Relay Replacement : Within an Electrical Centre → Attached to Wire Harness |
• | Control Module References for HVAC control module and radio/HVAC control replacement, programming and setup |
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