Toyota Tundra Service Manual: ECM Power Source Circuit

DESCRIPTION

When the ignition switch is turned to ON, the battery voltage is applied to the IGSW terminal of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the integration relay (EFI relay) and supplying power to terminals +B and +B2 of the ECM.

WIRING DIAGRAM

PROCEDURE

1.

INSPECT FUSES (AM2, IG2 MAIN, EFI NO. 1, IGN)

(a) Remove the IG2 MAIN fuse, EFI NO. 1 fuse and IGN fuse from the engine room relay block.

(b) Remove the AM2 fuse from the driver side junction block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

AM2 fuse

Always

Below 1 Ω

IG2 MAIN fuse

Always

Below 1 Ω

EFI NO. 1 fuse

Always

Below 1 Ω

IGN fuse

Always

Below 1 Ω

NG

CHECK FOR SHORT IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE

OK

2.

INSPECT INTEGRATION RELAY (IG2, EFI)

(a) Remove the integration relay from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2C-1 - 2B-8

No battery voltage is applied to terminals 2B-6 and 2B-7

10 kΩ or higher

2C-1 - 2B-8

Battery voltage is applied to terminals 2B-6 and 2B-7

Below 1 Ω

2C-1 - 2B-4

No battery voltage is applied to terminals 2B-2 and 2B-3

10 kΩ or higher

2C-1 - 2B-4

Battery voltage is applied to terminals 2B-2 and 2B-3

Below 1 Ω

NG

REPLACE INTEGRATION RELAY

OK

3.

CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)

(a) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

D74-81 (E1) - Body ground

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

INSPECT ECM (IGSW VOLTAGE)

(a) Disconnect the ECM connectors.

(b) Turn the ignition switch to ON.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A24-28 (IGSW) - D74-81 (E1)

Ignition switch ON

11 to 14 V

OK

REPLACE ECM

NG

5.

CHECK HARNESS AND CONNECTOR (RELAY BLOCK - ECM, IGNITION SWITCH, BATTERY AND BODY GROUND)

(a) Disconnect the ECM connector.

(b) Disconnect the ignition switch connector.

(c) Disconnect the cable from the battery negative (-) terminal.

(d) Disconnect the cable from the battery positive (+) terminal.

(e) Remove the AM2 fuse and integration relay.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A24-28 (IGSW) - 2B-8

Always

Below 1 Ω

2B-7 - Body ground

Always

Below 1 Ω

Positive (+) battery cable - 2C-1

Always

Below 1 Ω

Positive (+) battery cable - AM2 fuse terminal 1

Always

Below 1 Ω

J9-5 (AM2) - AM2 fuse terminal 2

Always

Below 1 Ω

J9-6 (IG2) - 2B-6

Always

Below 1 Ω

A24-28 (IGSW) or 2B-8 - Body ground

Always

10 kΩ or higher

Positive (+) battery cable or 2C-1 - Body ground

Always

10 kΩ or higher

Positive (+) battery cable or AM2 fuse terminal 1 - Body ground

Always

10 kΩ or higher

J9-5 (AM2) or AM2 fuse terminal 2 - Body ground

Always

10 kΩ or higher

J9-6 (IG2) or 2B-6 - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

6.

INSPECT IGNITION SWITCH

(a) Inspect the ignition switch (See page ).

NG

REPLACE IGNITION SWITCH

OK

7.

CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - ECM, BATTERY AND BODY GROUND)

(a) Disconnect the ECM connector.

(b) Disconnect the cable from the battery negative (-) terminal.

(c) Disconnect the cable from the battery positive (+) terminal.

(d) Remove the integration relay from the engine room relay block.

(e) Disconnect the integration relay connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

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

Always

Below 1 Ω

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

Always

Below 1 Ω

A24-34 (MREL) - 2B-2

Always

Below 1 Ω

2C-1 - Positive (+) battery cable

Always

Below 1 Ω

2B-3 - Body ground

Always

Below 1 Ω

A24-3 (+B) or 2B-4 - Body ground

Always

10 kΩ or higher

A24-2 (+B2) or 2B-4 - Body ground

Always

10 kΩ or higher

A24-34 (MREL) or 2B-2 - Body ground

Always

10 kΩ or higher

2C-1 or Positive (+) battery cable - Body ground

Always

10 kΩ or higher

OK

REPAIR OR REPLACE ENGINE ROOM RELAY BLOCK

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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