Toyota 4Runner manuals

Toyota 4Runner: Lost Communication with ECM / PCM "A" (U0100)

Toyota 4Runner Service Manual / Power Source / Network / Networking / Can Communication System / Lost Communication with ECM / PCM "A" (U0100)

DESCRIPTION

DTC Code

DTC Detection Condition

Trouble Area

U0100

There is no communication from the ECM.

  • Power source or inside ECM
  • ECM main wire or connector
  • ECM

HINT:

For vehicles with a smart key system only.

WIRING DIAGRAM


CAUTION / NOTICE / HINT

NOTICE:

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

HINT:

Operating the ignition switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.

PROCEDURE

1.

DISCONNECT CABLE FROM NEGATIVE BATTERY TERMINAL

(a) Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the main wire and branch wire.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

NOTICE:

When disconnecting the cable, some systems need to be initialized after the cable is reconnected (See page ).



NEXT

2.

CHECK FOR OPEN IN CAN BUS MAIN WIRE (ECM MAIN WIRE)

(a) Disconnect the F50 ECM connector.


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

Standard Resistance:

Tester Connection

Switch Condition

Specified Condition

F50-34 (CANP) - F50-33 (CANN)

Ignition switch off

108 to 132 Ω

Text in Illustration

*a

Rear view of wire harness connector

(to ECM)


NG

REPAIR OR REPLACE ECM MAIN WIRE OR CONNECTOR (CANP, CANN)


OK

3.

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

(a) Connect the cable to the negative (-) battery terminal.

NOTICE:

When disconnecting the cable, some systems need to be initialized after the cable is reconnected (See page ).


Text in Illustration

*a

Front view of wire harness connector

(to ECM)

-

-

(b) Disconnect the B38, B39 and F51 ECM connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

B38-12 (E1) - Body ground

Always

Below 1 Ω

B39-14 (E01) - Body ground

Always

Below 1 Ω

B39-15 (E02) - Body ground

Always

Below 1 Ω

B39-10 (ME01) - Body ground

Always

Below 1 Ω

F51-12 (EC) - Body ground

Always

Below 1 Ω

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

F51-24 (BATT) - Body ground

Always

11 to 14 V

F51-23 (+B2) - Body ground

Battery positive (+) voltage applied to terminal F51-9 (MREL)

11 to 14 V

F51-22 (+B) - Body ground

Battery positive (+) voltage applied to terminal F51-9 (MREL)

11 to 14 V


OK

REPLACE ECM


NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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