VC Output Circuit

3UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: VC Output Circuit

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 is short-circuited, the microprocessor in the ECM and sensors that are supplied power through the VC circuit are deactivated because the power is not supplied from the VC circuit. Under this condition, the system does not start up and the MIL does not illuminate even if the system malfunctions.
HINT: Under normal conditions, the MIL is illuminated for several seconds when the ignition switch is first turned ON. The MIL goes off when the engine is started.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK MIL
(a) Check that the MIL lights up when turning the ignition switch ON.
OK:
MIL lights up
OK -- SYSTEM OK
NG -- Continue to next step.
2. CHECK CONNECTION BETWEEN TECHSTREAM AND ECM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and tester ON.
(c) Check the communication between the Techstream and ECM.
Result:






B -- GO TO MIL CIRCUIT
A -- Continue to next step.
3. CHECK ECM (VC VOLTAGE)




(a) Turn the ignition switch ON.
(b) Measure the voltage of the ECM connector.
Result:
Voltage is not 5 V
NEXT -- Continue to next step.
4. CHECK MIL (THROTTLE POSITION SENSOR)
(a) Disconnect the T26 throttle body connector.
(b) Turn the ignition switch ON.
(c) Check the MIL.
Result:






B -- REPLACE THROTTLE BODY ASSEMBLY
A -- Continue to next step.
5. CHECK MIL (CANISTER PUMP MODULE)
(a) Disconnect the C12 canister pump module connector.
(b) Turn the ignition switch ON.
(c) Check the MIL.
Result:






B -- REPLACE CANISTER
A -- Continue to next step.
6. CHECK WIRE HARNESS (ECM - BODY GROUND)




(a) Disconnect the T26 throttle body connector.
(b) Disconnect the C12 canister pump module connector.
(c) Disconnect the E2 ECM connector.
(d) Measure the resistance of the wire harness connector.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS AND CONNECTOR
OK -- REPLACE ECM