Toyota Tundra Service Manual: VC Output Circuit

DESCRIPTION

The ECM constantly generates 5 V power from the battery voltage supplied to the +B (BATT) terminal to operate the microprocessor. The ECM also provides this power to the sensors through the VC output circuit.

When the VC circuit has a short circuit, the microprocessor in the ECM and sensors that are supplied power through the VC circuit are deactivated because power is not supplied from the VC circuit. When the system is in this condition, it will not start.

WIRING DIAGRAM

  • For the circuit diagram of the ECM power source circuit.

    Click here

  • VC Power Source Circuit

CAUTION / NOTICE / HINT

HINT:

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

PROCEDURE

1.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

B

2.

CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI NO. 2)

(a) Turn the ignition switch to ON.

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

Standard voltage:

Tester Connection

Switch Condition

Specified Condition

EFI NO. 2 fuse terminal - Body ground

Ignition switch ON

11 to 14 V

HINT:

Check the fuse with it installed to the engine room relay block and junction block assembly.

NG

GO TO ECM POWER SOURCE CIRCUIT

OK

3.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (THROTTLE POSITION SENSOR)

(a) Disconnect the throttle with motor body assembly connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

HINT:

Perform "Inspection After Repair" after replacing the throttle with motor body assembly (See page ).

A

REPLACE THROTTLE WITH MOTOR BODY ASSEMBLY

B

4.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (ACCELERATOR PEDAL POSITION SENSOR)

(a) Disconnect the accelerator pedal sensor assembly connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE ACCELERATOR PEDAL SENSOR ASSEMBLY

B

5.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (CANISTER PUMP MODULE)

(a) Disconnect the canister pump module connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE CANISTER PUMP MODULE

B

6.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (AIR SWITCHING VALVE for Bank 1)

(a) Disconnect the air switching valve assembly connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE AIR SWITCHING VALVE ASSEMBLY (FOR BANK 1)

B

7.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (AIR SWITCHING VALVE for Bank 2)

(a) Disconnect the air switching valve assembly connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE AIR SWITCHING VALVE ASSEMBLY (FOR BANK 2)

B

8.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (POWER STEERING OIL PRESSURE SENSOR)

(a) Disconnect the power steering oil pressure sensor connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE POWER STEERING OIL PRESSURE SENSOR

B

9.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (CAMSHAFT POSITION SENSOR)

(a) Disconnect the camshaft position sensor connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE CAMSHAFT POSITION SENSOR

B

10.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (CRANKSHAFT POSITION SENSOR)

(a) Disconnect the crankshaft position sensor connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE CRANKSHAFT POSITION SENSOR

B

11.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (VVT SENSOR FOR INTAKE SIDE OF BANK 1)

(a) Disconnect the VVT sensor (for Intake Side of Bank 1) connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE VVT SENSOR (FOR INTAKE SIDE OF BANK 1)

B

12.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (VVT SENSOR FOR EXHAUST SIDE OF BANK 1)

(a) Disconnect the VVT sensor (for Exhaust Side of Bank 1) connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE VVT SENSOR (FOR EXHAUST SIDE OF BANK 1)

B

13.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (VVT SENSOR FOR INTAKE SIDE OF BANK 2)

(a) Disconnect the VVT sensor (for Intake Side of Bank 2) connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE VVT SENSOR (FOR INTAKE SIDE OF BANK 2)

B

14.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (VVT SENSOR FOR EXHAUST SIDE OF BANK 2)

(a) Disconnect the VVT sensor (for Exhaust Side of Bank 2) connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE VVT SENSOR (FOR EXHAUST SIDE OF BANK 2)

B

15.

CHECK COMMUNICATION BETWEEN TECHSTREAM AND ECM (MANIFOLD ABSOLUTE PRESSURE SENSOR)

(a) Disconnect the manifold absolute pressure sensor connector.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Check the communication between the Techstream and ECM.

HINT:

It can be checked using the "Engine and ECT" item of the Data List.

Result

Result

Proceed to

Communication is possible

A

Communication is not possible

B

A

REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR

B

16.

CHECK HARNESS AND CONNECTOR

(a) Disconnect the throttle with motor body assembly connector.

(b) Disconnect the accelerator pedal sensor assembly connector.

(c) Disconnect the canister pump module connector.

(d) Disconnect the air switching valve assembly (for Bank 1) connector.

(e) Disconnect the air switching valve assembly (for Bank 2) connector.

(f) Disconnect the power steering oil pressure sensor connector.

(g) Disconnect the camshaft position sensor connector.

(h) Disconnect the crankshaft position sensor connector.

(i) Disconnect the VVT sensor (for Intake Side of Bank 1) connector.

(j) Disconnect the VVT sensor (for Exhaust Side of Bank 1) connector.

(k) Disconnect the VVT sensor (for Intake Side of Bank 2) connector.

(l) Disconnect the VVT sensor (for Exhaust Side of Bank 2) connector.

(m) Disconnect the manifold absolute pressure sensor connector.

(n) Disconnect the integration relay connector.

(o) Disconnect the ECM connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

D74-80 (VCTA) - Body ground

Always

10 kΩ or higher

A24-57 (VCPA) - Body ground

Always

10 kΩ or higher

A24-59 (VCP2) - Body ground

Always

10 kΩ or higher

D74-66 (VCV2) - Body ground

Always

10 kΩ or higher

D74-67 (VCV1) - Body ground

Always

10 kΩ or higher

A24-3 (+B) - Body ground

Always

10 kΩ or higher

A24-2 (+B2) - Body ground

Always

10 kΩ or higher

A24-3 (+B) - 2B-4

Always

Below 1 Ω

A24-2 (+B2) - 2B-4

Always

Below 1 Ω

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

    Terminals Of Ecm

    Throttle Body

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