Lexus NX: Steering Wheel does not Heat Up When Heated Steering Wheel Switch is Pressed
DESCRIPTION
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WIRING DIAGRAM
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CAUTION / NOTICE / HINT
HINT:
- Inspect the fuses for circuits related to this system before performing the following inspection procedure.
- The steering wheel heater unit is built into the steering wheel assembly which cannot be disassembled. Therefore, when the steering wheel heater unit has a malfunction, replace the steering wheel assembly.
PROCEDURE
| 1. | INSPECT STEERING WHEEL HEATER UNIT (THERMISTOR/HEATER/THERMOSTAT) |
| (a) Disconnect the B steering vibration and heater ECU connector. |
|
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| B-3 (TH1) - B-2 (TH2) | 10 to 30°C (50 to 86°F) | 8.132 to 18.43 kΩ |
| B-5 (SH1) - B-1 (SH2) | 20°C (68°F) | 1.91 to 2.25 Ω |
| NG | .gif) | REPLACE STEERING WHEEL ASSEMBLY |
|
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| 2. | INSPECT SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY |
(a) Check the connectors and cables of the spiral cable with sensor sub-assembly.
OK:
There are no defects such as scratches, cracks, dents or damage on the connectors or cables.
(b) Disconnect the I156 and z18 spiral cable with sensor sub-assembly connectors.
(c) Measure the resistance according to the value(s) in the table below.
| *a | Component without harness connected (Spiral Cable with Sensor Sub-assembly) | - | - |
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| z18-2 - I156-1 (BTM) | Always | 3 Ω or less |
| z18-3 - I156-3 (ETM) | Always | 3 Ω or less |
| z18-1 - I156-2 (EHT) | Always | 0.02 to 0.28 Ω |
| z18-4 - I156-4 (BHT) | Always | 0.02 to 0.28 Ω |
| NG | | REPLACE SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY |
|
| 3. | INSPECT NO. 2 COMBINATION SWITCH ASSEMBLY (STEERING HEATER SWITCH) |
(a) Remove the No. 2 combination switch assembly.
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(b) Inspect the No. 2 combination switch assembly (steering heater switch).
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| NG | | REPLACE NO. 2 COMBINATION SWITCH ASSEMBLY |
|
| 4. | CHECK STEERING HEATER RELAY |
| (a) Remove the STRG HTR relay from the No. 2 engine room relay block. |
|
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 3 - 5 | Voltage is not applied between terminals 1 and 2 | 10 kΩ or higher |
| 3 - 5 | Voltage is applied between terminals 1 and 2 | Below 1 Ω |
| NG | | REPLACE STEERING HEATER RELAY |
|
| 5. | CHECK HARNESS AND CONNECTOR (NO. 2 COMBINATION SWITCH ASSEMBLY - SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY) |
(a) Disconnect the I37 No. 2 combination switch assembly connector.
(b) Disconnect the I156 spiral with sensor cable sub-assembly connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| I37-16 (ECU) - I156-3 (ETM) | Always | Below 1 Ω |
| I37-9 (IND) - I156-1 (BTM) | Always | Below 1 Ω |
| I37-16 (ECU) or I156-3 (ETM) - Body ground | Always | 10 kΩ or higher |
| I37-9 (IND) or I156-1 (BTM) - Body ground | Always | 10 kΩ or higher |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 6. | CHECK HARNESS AND CONNECTOR (STRG HTR RELAY - SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY) |
(a) Remove the STRG HTR relay from the No. 2 engine room relay block.
(b) Disconnect the I156 spiral with sensor cable sub-assembly connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 5 - I156-4 (BHT) | Always | Below 1 Ω |
| 5 or I156-4 (BHT) - Body ground | Always | 10 kΩ or higher |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 7. | CHECK HARNESS AND CONNECTOR (NO. 2 COMBINATION SWITCH ASSEMBLY POWER SOURCE) |
| (a) Disconnect the I37 No. 2 combination switch assembly connector. |
|
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Switch Condition | Specified Condition |
|---|---|---|
| I37-4 (IG1) - Body ground | Power switch on (IG) | 11 to 14 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 8. | CHECK HARNESS AND CONNECTOR (STRG HTR RELAY POWER SOURCE) |
(a) Remove the STRG HTR relay from the No. 2 engine room relay block.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 3 - Body ground | Always | 11 to 14 V |
| 1 - Body ground | Power switch on (IG) | 11 to 14 V |
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| 2 - Body ground | Always | Below 1 Ω |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 9. | CHECK HARNESS AND CONNECTOR (SPIRAL WITH SENSOR CABLE SUB-ASSEMBLY BODY GROUND) |
(a) Disconnect the I156 spiral with sensor cable sub-assembly connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| I156-2 (EHT) - Body ground | Always | Below 1 Ω |
| OK | | REPLACE STEERING VIBRATION AND HEATER ECU |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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