Lexus NX manuals

Lexus NX: Low or High Power Supply Voltage (C1241,C1242)

Lexus NX Service Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System / Low or High Power Supply Voltage (C1241,C1242)

DESCRIPTION

If a malfunction is detected in the power supply circuit, the skid control ECU (brake booster with master cylinder assembly) power source voltage drops, or there is insufficient voltage to operate the ABS main relay, the skid control ECU (brake booster with master cylinder assembly) will store these DTCs.

These DTCs may also be stored if the auxiliary battery voltage drops below 9.5 V.

HINT:

DTC C1256 (Accumulator Low Pressure) may also be memorized if there is a drop in power source voltage.

DTC No.

Detection Item

INF Code

DTC Detection Condition

Trouble Area

Note

C1241

Low or High Power Supply Voltage

101

102

551

552

553
  • INF Code: 101
    • Any of the following is detected when the BS terminal voltage is 9.3 V or less:
      1. Vehicle not decelerated (brake pedal is not depressed) for 3 seconds or more.
      2. While depressing the brake pedal, linear solenoid current does not satisfy 1.34 A.
      3. Vehicle decelerated (brake pedal is depressed) for 0.06 seconds.
  • INF Code: 102
    • Any of the following is detected when the ECU internal voltage is 6.8 V or less:
      1. When main relay ON is requested, voltage of the relay connection does not exceed 3.5 V for 0.22 seconds or more.
      2. Sensor supply voltage is 4.75 V or less, or 5.25 V or more for 0.06 seconds.
      3. Accumulator pressure sensor output voltage is 4.54 V or less, or 5.46 V or more for 0.06 seconds.
  • INF Code: 551
    • When driving at 3 km/h (1.9 mph) or more, IG1 terminal voltage is 9.5 V or less, or VM1 voltage is 8.6 V or less for 10 seconds or more.
  • INF Code: 552
    • When VM1 voltage is 8.6 V or less, sensor supply voltage is low for 60 seconds or more.
  • INF Code: 553
    • VM1 voltage is 16.6 V or more for 0.8 seconds.
  • Improperly connected connector, deformation or corrosion of terminals
  • Auxiliary battery
  • Hybrid control system (Charging circuit)
  • Skid control ECU (Brake booster with master cylinder assembly)

-

C1242

Open Circuit in IG1/IG2 Power Source Circuit

111

112
  • INF Code: 111
    • Voltage is not applied to the IG1 terminal (less than 3.5 V), and applied to the IG2 terminal (9.5 V or more) for 4 seconds or more.
  • INF Code: 112
    • Voltage is not applied to the IG2 terminal (less than 3.5 V), and applied to the IG1 terminal (9.5 V or more) for 4 seconds or more.
  • INF Code: 111
    • Open or short in IG1 circuit
    • Improperly connected connector, deformation or corrosion of terminals
    • Smart access system with push-button start (IG start circuit)
    • Auxiliary battery
    • Hybrid control system (Charging circuit)
    • Skid control ECU (Brake booster with master cylinder assembly)
  • INF Code: 112
    • Open or short in IG2 circuit
    • Improperly connected connector, deformation or corrosion of terminals
    • Smart access system with push-button start (IG start circuit)
    • Auxiliary battery
    • Hybrid control system (Charging circuit)
    • Skid control ECU (Brake booster with master cylinder assembly)

-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When replacing the skid control ECU (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

CHECK SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function)

(a) Check if smart access system with push-button start (for start function) DTCs are output.

Click here

Body Electrical > Smart Access > Trouble Codes

Result

Proceed to

DTCs are not output.

A

DTCs are output.

B
B

INSPECT SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function)

A

2.

CHECK HYBRID CONTROL SYSTEM

(a) Check if hybrid control system DTCs are output.

Click here

Powertrain > Hybrid Control > Trouble Codes

Result

Proceed to

DTCs are not output.

A

DTCs are output.

B
B

INSPECT HYBRID CONTROL SYSTEM

A

3.

CHECK DTC

(a) Check that no main relay malfunction DTCs are output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result

Proceed to

Main relay malfunction DTCs are not output.

A

Main relay malfunction DTCs are output.

B
B

REPAIR CIRCUITS INDICATED BY OUTPUT DTCS

A

4.

CHECK AUXILIARY BATTERY

(a) Check the auxiliary battery voltage.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

Auxiliary battery

Power switch on (IG)

11 to 14 V

Auxiliary battery

Power switch on (READY)

11 to 15.5 V
NG

CHARGE OR REPLACE AUXILIARY BATTERY
OK

5.

CHECK HARNESS AND CONNECTOR (POWER SOURCE TERMINAL)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connector.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

(b) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A57-14 (BI) - Body ground

Always

11 to 14 V

A57-15 (BS) - Body ground

Always

11 to 14 V

A57-16 (IG1) - Body ground

Power switch on (IG)

11 to 14 V

A57-12 (IG2) - Body ground

Power switch on (IG)

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
OK

6.

CHECK HARNESS AND CONNECTOR (GND TERMINAL)

(a) Turn the power switch off.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A57-28 (GND) - Body ground

Always

Below 1 Ω

A57-27 (GND2) - Body ground

Always

Below 1 Ω

A57-26 (GND3) - Body ground

Always

Below 1 Ω

A57-25 (GND4) - Body ground

Always

Below 1 Ω

A57-24 (GND5) - Body ground

Always

Below 1 Ω

A57-23 (GND6) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)
OK

7.

RECONFIRM DTC

(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(c) Turn the power switch off.

(d) Turn the power switch on (READY).

(e) Perform a road test.

(f) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result

Proceed to

DTCs C1241 and C1242 are not output.

A

DTCs C1241 and/or C1242 are output.

B

HINT:

If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.

Click here

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

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