Lexus NX: Power Steering ECU Communication Stop Mode

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Power Steering ECU Communication Stop Mode

DESCRIPTION

Detection Item

Symptoms

Trouble Area

Power Steering ECU Communication Stop Mode

Any of the following conditions are met:

  • Communication stop for "Power Steering (EPS)" is indicated on "Communication Bus Check".

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  • Communication system DTCs (DTCs that start with U) that are output correspond to "Power Steering ECU Communication Stop Mode" in "DTC Combination Table".

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  • Power steering ECU assembly CAN branch wire or connector
  • Power source circuit of power steering ECU assembly
  • Power steering ECU assembly ground circuit
  • Power steering ECU assembly
  • ECU wire sub-assembly

WIRING DIAGRAM

for Power Tilt and Power Telescopic Steering Column: for Manual Tilt and Manual Telescopic Steering Column:

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.
  • Before measuring the resistance of the CAN bus, turn the power switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal.

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  • When disconnecting and reconnecting the auxiliary battery.

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    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

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  • Some parts must be initialized and set when replacing or removing and installing parts.

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  • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.

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  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

    DTC check procedure: Turn the power switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.

  • After the repair, perform CAN Bus Check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.

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HINT:

  • Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE

1.

CHECK VEHICLE TYPE

(a) Check vehicle type.

Result

Proceed to

for Power Tilt and Power Telescopic Steering Column

A

for Manual Tilt and Manual Telescopic Steering Column

B

B

GO TO STEP 7

A

2.

CHECK FOR OPEN IN CAN BUS WIRE (POWER STEERING ECU ASSEMBLY BRANCH WIRE)

(a) Disconnect the cable from the negative (-) auxiliary battery terminal.

(b) Disconnect the power steering ECU assembly connector.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

n2-7 (CANH) - n2-8 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω

NG

GO TO STEP 6

OK

3.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Reconnect the cable to the negative (-) auxiliary battery terminal.

*a

Front view of wire harness connector

(to ECU Wire Sub-assembly)

(b) Disconnect the ECU wire sub-assembly connector.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

An1-1 (PIG) - Body ground

Power switch off

9 to 16 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK

4.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the ECU wire sub-assembly connector.

*a

Front view of wire harness connector

(to ECU Wire Sub-assembly)

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

nl1-5 (IG) - Body ground

Power switch on (IG)

11 to 14 V

Power switch off

Below 1 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK

5.

CHECK ECU WIRE SUB-ASSEMBLY

(a) Reconnect the ECU wire sub-assembly connectors.

(b) Disconnect the power steering ECU assembly connectors.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

n2-1 (IG) - Body ground

Power switch on (IG)

8 to 16 V

Power switch off

Below 1 V

n1-1 (PIG) - Body ground

Power switch off

9 to 16 V

(d) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

n1-2 (PGND) - Body ground

Always

Below 1 Ω

OK

REPLACE POWER STEERING ECU ASSEMBLY

NG

REPLACE ECU WIRE SUB-ASSEMBLY

6.

CHECK FOR OPEN IN CAN BRANCH WIRE

(a) Disconnect the ECU wire sub-assembly connector.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

nl1-1 (CANH) - nl1-2 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω

OK

REPLACE ECU WIRE SUB-ASSEMBLY

NG

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR

7.

CHECK FOR OPEN IN CAN BUS WIRE (POWER STEERING ECU ASSEMBLY BRANCH WIRE)

(a) Disconnect the cable from the negative (-) auxiliary battery terminal.

(b) Disconnect the power steering ECU assembly connector.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

n3-4 (CANH) - n3-8 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω

NG

GO TO STEP 11

OK

8.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Reconnect the cable to the negative (-) auxiliary battery terminal.

*a

Front view of wire harness connector

(to ECU Wire Sub-assembly)

(b) Disconnect the ECU wire sub-assembly connector.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

An1-1 (PIG) - Body ground

Power switch off

9 to 16 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK

9.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the ECU wire sub-assembly connector.

*a

Front view of wire harness connector

(to ECU Wire Sub-assembly)

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

nl1-5 (IG) - Body ground

Power switch on (IG)

11 to 14 V

Power switch off

Below 1 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK

10.

CHECK ECU WIRE SUB-ASSEMBLY

(a) Reconnect the ECU wire sub-assembly connectors.

(b) Disconnect the power steering ECU assembly connectors.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

n3-1 (IG) - Body ground

Power switch on (IG)

8 to 16 V

Power switch off

Below 1 V

n1-1 (PIG) - Body ground

Power switch off

9 to 16 V

(d) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

n1-2 (PGND) - Body ground

Always

Below 1 Ω

OK

REPLACE POWER STEERING ECU ASSEMBLY

NG

REPLACE ECU WIRE SUB-ASSEMBLY

11.

CHECK FOR OPEN IN CAN BUS WIRE (POWER STEERING ECU ASSEMBLY BRANCH WIRE)

(a) Disconnect the ECU wire sub-assembly connector.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

nl1-1 (CANH) - nl1-2 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω

OK

REPLACE ECU WIRE SUB-ASSEMBLY

NG

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR

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