Lexus NX: Rear Motor High-voltage Circuit
DESCRIPTION
The cause of this malfunction may be the high-voltage circuit of the rear motor.
Check the rear motor internal resistance and the connection condition of the high-voltage line between the inverter and rear motor to check whether there is an open or short circuit.
Related Parts Check| Area | Inspection | Step |
|---|---|---|
| Rear motor cable connection check | Check for open circuit in the connection condition of the cable from the inverter to the rear motor. | 1, 3 |
| Rear motor, rear motor cable, extension wire | Check the rear motor (including cable) internal resistance and the insulation resistance with body ground to check for an open or short circuit. | 2 |
| Rear motor cable | Check for open or short in rear motor cable. | 4 |
| Extension wire | Check for open or short circuit in extension wire. | 5 |
WIRING DIAGRAM
CAUTION / NOTICE / HINT
This step is referenced from the procedures for each DTC.
If the inspection results below are normal, perform the next procedure for the referenced DTC.
CAUTION:
- Before inspecting the high-voltage system or disconnecting the low voltage connector of the inverter with converter assembly, take safety precautions such as wearing insulated gloves and removing the service plug grip to prevent electrical shocks. After removing the service plug grip, put it in your pocket to prevent other technicians from accidentally reconnecting it while you are working on the high-voltage system.
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After removing the service plug grip, wait for at least 10 minutes before touching any of the high-voltage connectors or terminals. After waiting for 10 minutes, check the voltage at the terminals in the inspection point in the inverter with converter assembly. The voltage should be 0 V before beginning work.
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HINT:
Waiting for at least 10 minutes is required to discharge the high-voltage capacitor inside the inverter with converter assembly.
NOTICE:
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.
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PROCEDURE
| 1. | CHECK INVERTER WITH CONVERTER ASSEMBLY (NO. 2 FRAME WIRE (REAR MOTOR CABLE) CONNECTION CONDITION) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
| (b) Remove the inverter cover UPR from the inverter with converter assembly. |
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| (c) Check that the bolts for the No. 2 frame wire (rear motor cable) are tightened to the specified torque, the No. 2 frame wire (rear motor cable) is connected securely, and there are no contact problems. Specified Condition: T = 8.0 N*m (82 kgf*cm, 71 in.*lbf) NOTICE: Make sure that the tightening torque of the bolt is between 6.4 and 9.6 N*m (65 and 98 kgf*cm, 57 and 85 in.*lbf). |
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(d) Disconnect the No. 2 frame wire (rear motor cable) from the inverter with converter assembly.
(e) Check for arc marks at the terminals for the generator cable.
| Result | Proceed to | |
|---|---|---|
| The terminals are connected securely and there are no contact problems. | There are no arc marks. | A |
| The terminals are not connected securely and there is a contact problem. | There are arc marks. | B |
| The terminals are not connected securely and there is a contact problem. | There are no arc marks. | C |
| The terminals are connected securely and there are no contact problems. | There are arc marks. | B |
(f) Connect the No. 2 frame wire (rear motor cable) to the inverter with converter assembly.
(g) Install the inverter cover UPR.
| B | .gif) | REPLACE MALFUNCTIONING PARTS |
| C | | CONNECT SECURELY |
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| 2. | CHECK REAR TRACTION MOTOR WITH TRANSAXLE ASSEMBLY (REAR MOTOR (MGR)) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
| (b) Remove the inverter cover UPR from the inverter with converter assembly. |
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| (c) Disconnect the No. 2 frame wire (rear motor cable) from the inverter with converter assembly. |
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| (d) Check the rear motor (MGR) for an interphase short using a milliohmmeter. (1) Using a milliohmmeter, measure the resistance according to the value(s) in the table below. HINT: If the rear motor (MGR) temperature is high, the resistance will vary greatly from the specification. Therefore, measure the resistance at least 8 hours after the vehicle is stopped. Standard Resistance:
HINT: To correct the variation of the measured resistance due to temperature, use the following formula to calculate the resistance at 20°C (68°F). R20 = Rt / {1 + 0.00393 X (T - 20)} The calculation is based on the following: R20: Resistance at 20°C (68°F) (mΩ) Rt: Measured resistance (mΩ) T: Temperature when the resistance is measured (°C (°F).) |
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(e) When checking for a short circuit between rear motor phases without using a milliohmmeter.
NOTICE:
The rear motor generates current when wheels are rotated by hand. Before performing the inspection, wrap the rear motor cable terminals with tape (non-residue type) or equivalent.
HINT:
A short circuit between the rear motor phases can be checked simply without using a milliohmmeter.
(1) Connect the cable to the negative (-) auxiliary battery terminal.
(2) Turn the power switch on (IG).
NOTICE:
Turning the power switch on (IG) with the service plug grip removed causes other DTCs to be stored. Clear the DTCs after performing this inspection.
(3) Move the shift lever to N.
(4) Lift up the vehicle.
(5) Rotate the rear wheels in the same direction simultaneously by hand.
Standard:
Left and right wheels rotate smoothly (No short circuit between phases)
HINT:
If a short circuit exists between the rear motor phases, the rear wheels do not rotate smoothly (some resistance is felt).
(6) Lower the vehicle.
(7) Move the shift lever to P.
(8) Turn the power switch off.
(9) Disconnect the cable from the negative (-) auxiliary battery terminal.
(f) Using a megohmmeter set to 500 V, measure the resistance according to the value(s) in the table below.
NOTICE:
Be sure to set the megohmmeter to 500 V when performing this test. Using a setting higher than 500 V can result in damage to the component being inspected.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| t1-1 (R-W) - Body ground and shield ground | Power switch off | 100 MΩ or higher |
| t1-2 (R-V) - Body ground and shield ground | Power switch off | 100 MΩ or higher |
| t1-3 (R-U) - Body ground and shield ground | Power switch off | 100 MΩ or higher |
(g) Measure the resistance according to the value(s) in the table below.
HINT:
Perform this procedure only when checking for a short circuit between rear motor phases without using a milliohmmeter.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| t1-1 (R-W) - t1-2 (R-V) | Power switch off | Below 1 Ω |
| t1-2 (R-V) - t1-3 (R-U) | Power switch off | Below 1 Ω |
(h) Reconnect the No. 2 frame wire (rear motor cable).
(i) Install the inverter cover UPR.
| OK | | REAR MOTOR HIGH-VOLTAGE CIRCUIT NORMAL (PERFORM NEXT STEP FOR REFERENCED DTC) |
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| 3. | CHECK REAR TRACTION MOTOR WITH TRANSAXLE ASSEMBLY (NO. 2 FRAME WIRE (REAR MOTOR CABLE) CONNECTION CONDITION) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
| (b) Check that the bolts for the No. 2 frame wire (rear motor cable) are tightened to the specified torque, the No. 2 frame wire (rear motor cable) is connected securely, and there are no contact problems. Specified Condition: T = 15 N*m (153 kgf*cm, 11 ft.*lbf) NOTICE: Make sure that the tightening torque of the bolt is between 12 and 18 N*m (122 and 184 kgf*cm, 9 and 13 ft.*lbf). |
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(c) Disconnect the No. 2 frame wire (rear motor cable) from the rear traction motor with transaxle assembly
(d) Check for arc marks at the bolts for the No. 2 frame wire (rear motor cable).
| Result | Proceed to | |
|---|---|---|
| The terminals are connected securely and there are no contact problems. | There are no arc marks. | A |
| The terminals are not connected securely and there is a contact problem. | There are arc marks. | B |
| The terminals are not connected securely and there is a contact problem. | There are no arc marks. | C |
| The terminals are connected securely and there are no contact problems. | There are arc marks. | B |
(e) Connect the No. 2 frame wire (rear motor cable).
| B | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
| C | | CONNECT SECURELY |
|
| 4. | CHECK NO. 2 FRAME WIRE (REAR MOTOR CABLE) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
| (b) Remove the inverter cover UPR from the inverter with converter assembly. |
|
| (c) Disconnect the No. 2 frame wire (rear motor cable) from the inverter with converter assembly. |
|
| (d) Disconnect the No. 2 frame wire (rear motor cable) from the rear traction motor with transaxle assembly. |
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| (e) Using a megohmmeter set to 500 V, measure the resistance according to the value(s) in the table below. NOTICE: Be sure to set the megohmmeter to 500 V when performing this test. Using a setting higher than 500 V can result in damage to the component being inspected. Standard Resistance:
NOTICE: Wrap the terminals of three-phase AC cable with insulating tape to avoid them coming into contact with body ground. |
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| (f) Measure the resistance according to the value(s) in the table below. Standard Resistance:
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(g) Connect the No. 2 frame wire (rear motor cable) to the rear traction motor with transaxle assembly.
(h) Connect the No. 2 frame wire (rear motor cable) to the inverter with converter assembly.
(i) Install the inverter cover UPR.
| NG | | REPLACE NO. 2 FRAME WIRE |
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| 5. | CHECK EXTENSION WIRE ASSEMBLY |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
(b) Remove the extension wire assembly from the rear traction motor with transaxle assembly.
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| (c) Using a megohmmeter set to 500 V, measure the resistance according to the value(s) in the table below. NOTICE: Be sure to set the megohmmeter to 500 V when performing this test. Using a setting higher than 500 V can result in damage to the component being inspected. Standard Resistance:
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(d) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| R-U - R-U | Power switch off | Below 1 Ω |
| R-V - R-V | Power switch off | Below 1 Ω |
| R-W - R-W | Power switch off | Below 1 Ω |
| R-U - R-V | Power switch off | 100 kΩ or higher |
| R-V - R-W | Power switch off | 100 kΩ or higher |
| R-W - R-U | Power switch off | 100 kΩ or higher |
(e) Install the extension wire.
| OK | | REPLACE REAR TRACTION MOTOR WITH TRANSAXLE ASSEMBLY |
| NG | | REPLACE EXTENSION WIRE ASSEMBLY |
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