ECM Power Source Circuit
3MZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: ECM Power Source Circuit
ECM Power Source Circuit
DESCRIPTION
When the ignition switch is turned to the ON position, the battery voltage is applied to terminal IGSW of the ECM (Included in HV control ECU). The ECM MREL output signal causes a current to flow to the coil, closing the contacts of the IGCT relay and supplying power to terminal +B of the ECM.
If the ignition switch is turned off, the ECM holds the IGCT relay ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.
When the ignition switch is turned ON, voltage from the ECM's MREL terminal flows to the IGCT relay. This causes the contacts of the IGCT relay to close, which supplies power to terminal +B or +B1 of the ECM.
WIRING DIAGRAM
INSPECTION PROCEDURE
PROCEDURE
1. INSPECT HV CONTROL ECU (+B, +B1 VOLTAGE)
(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the H34 and H31 HV control ECU connectors.
Standard voltage:
OK -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
NG -- Continue to next step.
2. CHECK HARNESS AND CONNECTOR (HV CONTROL ECU - BODY GROUND)
(a) Disconnect the H31 HV control ECU connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
(c) Reconnect the HV control ECU connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
3. INSPECT HV CONTROL ECU (IGSW VOLTAGE)
(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the H29 and H31 HV control ECU connectors.
Standard voltage:
OK -- INSPECT HV CONTROL ECU (MREL VOLTAGE)
NG -- Continue to next step.
4. CHECK FUSE (IGN FUSE)
(a) Remove the IGN fuse from the instrument panel J/B.
(b) Measure the IGN fuse resistance.
Standard resistance:
Below 1 Ohms
(c) Reinstall the IGN fuse.
NG -- CHECK FOR SHORT IN ALL HARNESSES AND COMPONENTS CONNECTED TO FUSE
OK -- Continue to next step.
5. INSPECT IGNITION SWITCH ASSEMBLY
(a) Check for continuity between the connector terminals shown in the table below.
Standard:
NG -- REPLACE IGNITION SWITCH ASSEMBLY
OK -- CHECK AND REPLACE HARNESS AND CONNECTOR (IGNITION SWITCH ASSEMBLY - HV CONTROL ECU)
6. INSPECT HV CONTROL ECU (MREL VOLTAGE)
(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the H34 and H31 HV control ECU connectors.
Standard voltage:
NG -- REPLACE HV CONTROL ECU
OK -- Continue to next step.
7. CHECK FUSE (IGCT NO. 2 FUSE)
(a) Remove the IGCT No. 2 fuse from the R/B No. 3.
(b) Measure the IGCT No. 2 fuse resistance.
Standard resistance:
Below 1 Ohms
(c) Reinstall the IGCT No. 2 fuse.
NG -- CHECK FOR SHORT IN ALL HARNESSES AND COMPONENTS CONNECTED TO FUSE
OK -- Continue to next step.
8. INSPECT IGCT RELAY
(a) Remove the IGCT relay from the engine room R/B.
(b) Measure the IGCT relay resistance.
Standard resistance:
NG -- REPLACE IGCT RELAY
OK -- Continue to next step.
9. CHECK HARNESS AND CONNECTOR (IGCT RELAY- HV CONTROL ECU, IGCT RELAY - BODY GROUND)
(a) Check the harness and the connectors between the integration relay and the HV control ECU.
(1) Remove the IGCT relay from the engine room R/B.
(2) Disconnect the H34 HV control ECU connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
Standard resistance (Check for short):
(b) Check the harness and the connectors between the IGCT relay and body ground.
(1) Remove the IGCT relay from the engine room R/B.
(2) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK AND REPAIR HARNESS AND CONNECTOR (TERMINAL +B OF HV CONTROL ECU - BATTERY POSITIVE TERMINAL)