ECM Power Source Circuit

2TR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: ECM Power Source Circuit
- ECM Power Source Circuit

DESCRIPTION

When the ignition switch is turned to ON, the battery voltage is applied to terminal IGSW of the ECM. The ECM MREL output signal causes current to flow to the coil, closing the contacts of the EFI relay and supplying power to terminal +B of the ECM.

WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
After turning ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work Service Precautions.

PROCEDURE

1. INSPECT ECM (+B VOLTAGE)





(a) Turn the ignition switch to ON.

(b) Measure the voltage between the terminals of the ECM connectors.

Standard Voltage:





NG -- CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)

OK -- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Symptom Related Diagnostic Procedures

2. CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)





(a) Disconnect the cable from the negative battery terminal.

(b) Disconnect the E4 ECM connector.

(c) Check the resistance.

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. INSPECT ECM (IGSW VOLTAGE)





(a) Turn the ignition switch to ON.

(b) Measure the voltage between the terminals of the ECM connectors.

Standard Voltage:





Result





B -- INSPECT ECM (MREL VOLTAGE)
A -- Continue to next step.

4. CHECK FUSE (AM2 AND IGN)





(a) Check the AM2 fuse.

(1) Remove the AM2 fuse from the engine room R/B.

(2) Check the AM2 fuse resistance.

Standard resistance:

Below 1 Ohms

(b) Check the IGN fuse.

(1) Remove the IGN fuse from the driver side J/B.

(2) Check the IGN fuse resistance.

Standard resistance:

Below 1 Ohms

NG -- CHECK FOR SHORT IN ALL HARNESSES AND COMPONENTS CONNECTED TO FUSE
OK -- Continue to next step.

5. INSPECT IGNITION SWITCH ASSEMBLY





(a) Disconnect the I7 ignition switch assembly connector.

(b) Check the resistance.

Standard Resistance:





NG -- REPLACE IGNITION SWITCH ASSEMBLY

OK -- CHECK AND REPAIR HARNESS OR CONNECTOR (BATTERY - IGNITION SWITCH ASSEMBLY - ECM)

6. INSPECT ECM (MREL VOLTAGE)





(a) Turn the ignition switch to ON.

(b) Measure the voltage between the terminals of the ECM connectors.

Standard Voltage:





NG -- REPLACE ECM Removal
OK -- Continue to next step.

7. CHECK FUSE (EFI)





(a) Remove the EFI fuse from the engine room R/B.

(b) Check the EFI fuse resistance.

Standard resistance:

Below 1 Ohms

NG -- CHECK FOR SHORT IN ALL HARNESSES AND COMPONENTS CONNECTED TO FUSE
OK -- Continue to next step.

8. INSPECT EFI RELAY





(a) Remove the EFI relay from the engine room R/B.

(b) Check the EFI relay resistance.

Standard Resistance:





NG -- REPLACE EFI RELAY
OK -- Continue to next step.

9. CHECK HARNESS AND CONNECTOR (EFI RELAY - ECM, EFI RELAY - BODY GROUND)





(a) Check the harness and connector between the EFI relay and ECM.

(1) Remove the EFI relay from the engine room R/B.

(2) Disconnect the E8 ECM connector.

(3) Check the resistance.

Standard Resistance (Check for open):





Standard Resistance (Check for short):





(b) Check the harness and connector between the EFI relay and body ground.

(1) Remove the EFI relay from the engine room R/B.

(2) Check the resistance.

Standard Resistance (Check for open):





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- CHECK AND REPLACE HARNESS OR CONNECTOR (TERMINAL 5 OF EFI RELAY - BATTERY POSITIVE TERMINAL)