Toyota Tundra. Manual — part 21

Fig. 60: Identifying Open Circuit In Wire Harness
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

b. Check the resistance.

1. Disconnect connectors A and C and measure the resistance between them.

Standard resistance (Fig. 61)

RESISTANCE SPECIFIED CONDITIONS

Fig. 61: Measuring Resistance Between Connector A And C
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

HINT:

Measure the resistance while lightly shaking the wire harness vertically and horizontally.

If the results match the examples above, an open circuit exists between terminal 1 of
connector A and terminal 1 of connector C.

2. Disconnect connector B and measure the resistance between the connectors.

Standard resistance (Fig. 62)

Tester Connection

Specified Condition

Connector A terminal 1 - Connector C terminal 1 10 kohms or higher
Connector A terminal 2 - Connector C terminal 2

Below 1 ohms

2009 Toyota Tundra

2009 GENERAL INFORMATION Introduction - Tundra

RESISTANCE SPECIFIED CONDITIONS

If the results match the examples above, an open circuit exists between terminal 1 of
connector B2 and terminal 1 of connector C.

Fig. 62: Measuring Resistance Between Terminal 1 Of Connector B2 And Terminal 1
Of Connector C
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

c. Check the voltage.

1. In a circuit in which voltage is applied to the ECU connector terminal, an open circuit can be

checked by conducting a voltage check. With each connector still connected, measure the
voltage between the body ground and these terminals (in this order): 1) terminal 1 of
connector A; 2) terminal 1 of connector B; and 3) terminal 1 of connector C.

Fig. 63: Checking Voltage Between Connectors
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Standard voltage (Fig. 63)

VOLTAGE SPECIFIED CONDITIONS

Tester Connection

Specified Condition

Connector A terminal 1 - Connector B1 terminal 1

Below 1 ohms

Connector B2 terminal 1 - Connector C terminal 1 10 kohms or higher

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

5V

2009 Toyota Tundra

2009 GENERAL INFORMATION Introduction - Tundra

If the results match the examples above, an open circuit exists in the wire harness between
terminal 1 of connector B and terminal 1 of connector C.

3. CHECK FOR SHORT CIRCUIT

a. If the wire harness is ground shorted (Fig. 64), locate the section by conducting a resistance check

with the body ground (below).

Fig. 64: Checking For Short Circuit With Body Ground
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

b. Check the resistance with the body ground.

1. Disconnect connectors A and C and measure the resistance.

Fig. 65: Checking Resistance With Body Ground
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Standard resistance (Fig. 65)

RESISTANCE SPECIFIED CONDITIONS

Connector B terminal 1 - Body ground

5V

Connector C terminal 1 - Body ground

Below 1 V

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

Below 1 ohms

Connector A terminal 2 - Body ground 10 kohms or higher

2009 Toyota Tundra

2009 GENERAL INFORMATION Introduction - Tundra

HINT:

Measure the resistance while lightly shaking the wire harness vertically and horizontally.

If your results match the examples above, a short circuit exists between terminal 1 of
connector A and terminal 1 of connector C.

2. Disconnect connector B and measure the resistance.

Standard resistance (Fig. 66)

RESISTANCE SPECIFIED CONDITION

If the results match the examples above, a short circuit exists between terminal 1 of
connector B2 and terminal 1 of connector C.

Fig. 66: Measuring Resistance Between Connectors
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

4. CHECK AND REPLACE ECU

a. First, check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty.

Temporarily replace the ECU with a normally functioning one and check if the symptoms occur. If
the trouble symptoms disappear, replace the original ECU.

Tester Connection

Specified Condition

Connector A terminal 1 - Body ground

10 kohms or higher

Connector B2 terminal 1 - Body ground

Below 1 ohms

NOTE:



The connector should not be disconnected from the ECU. Perform
the inspection from the backside of the connector on the wire
harness side.



When no measuring condition is specified, perform the inspection
with the engine stopped and the ignition switch ON.



Check that the connectors are fully seated. Check for loose, corroded
or broken wires.

2009 Toyota Tundra

2009 GENERAL INFORMATION Introduction - Tundra