Toyota Tundra Service Manual: Power Supply Voltage Circuit (C1241)

Toyota Tundra Service Manual / Brake / Brake Control / Dynamic Control Systems / Trailer Brake Control System / Power Supply Voltage Circuit (C1241)

DESCRIPTION

If a malfunction is detected in the power supply circuit, the trailer brake control ECU (brake control with bracket relay) stores this DTC.

DTC No.

Detection Item

INF Code

DTC Detection Condition

Trouble Area

C1241

Power Supply Voltage Circuit

81

82
  • INF Code: 81 (Low power supply voltage malfaunction)
    • At a vehicle speed of 3 km/h or higher, the IG terminal voltage is continuously below 7.9 V for 5 seconds or more
  • INF Code: 82 (High power supply voltage malfaunction)
    • The IG terminal voltage continuously exceeds 17.8 V for 5 seconds or more with the ignition switch on
  • Trailer brake control ECU (Brake control with bracket relay)
  • Harness or connector
  • ECU-IG1 NO.2 fuse

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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

PROCEDURE

1.

CHECK BATTERY

(a) Check the battery voltage.

Standard Voltage:

Tester Connection

Condition

Specified Condition

Positive (+) terminal - Negative (-) terminal

Ignition switch off

11 to 14 V
NG

CHECK OR REPLACE CHARGING SYSTEM COMPONENT OR BATTERY

OK

2.

CHECK TERMINAL VOLTAGE (IG TERMINAL)

(a) Turn the ignition switch off.

*a

Front view of wire harness connector

(to Trailer Brake Control ECU (Brake Control with Bracket Relay))

(b) Disconnect the J172 trailer brake control ECU (brake control with bracket relay) connector.

(c) Inspect both the connector case and the terminal for deformation and corrosion.

OK:

No deformation or corrosion.

(d) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

J172-13 (IG) - Body ground

Ignition switch ON

11 to 14 V
NG

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

3.

CHECK HARNESS AND CONNECTOR (GND TERMINAL)

(a) Turn the ignition switch off.

*a

Front view of wire harness connector

(to Trailer Brake Control ECU (Brake Control with Bracket Relay))

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J172-20 (GND) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)
OK

4.

RECONFIRM DTC

(a) Reconnect the J172 trailer brake control ECU (brake control with bracket relay) connector.

(b) Clear the DTCs.

Click here

(c) Turn the ignition switch off.

(d) Turn the ignition switch to ON.

(e) Perform a road test.

(f) Check if the same DTC is output.

Click here

Result

Proceed to

DTCs C1241 is not output.

A

DTCs C1241 is output.

B
A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE CONTROL WITH BRACKET RELAY

    ECU Malfunction (C14A7)

    Acceleration Sensor Output Malfunction (C1245)

    See More:

    Toyota Tundra Service Manual > Cruise Control System: Fail-safe Chart
    FAIL-SAFE CHART HINT: If any of the following conditions are detected while the cruise control system is controlling vehicle speed, the system clears the vehicle speed stored in the ECM and cancels control of vehicle speed by the cruise control system. Auto Cancel Condition Warning Fail-safe Deactiv ...

    Toyota Tundra Owners Manual

    Toyota Tundra Service Manual

    © 2025 Copyright www.ttundra.com
    0.0378