Diagnosis Item 21: Diagnose when the M.U.T.-III cannot receive the data sent by engine-ECU.


caution When servicing a CAN bus line, earth yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.

FUNCTION


The diagnostic result demonstrates that "the M.U.T.-III cannot receive the sent data from the engine-ECU" when the M.U.T.-III checks the periodically sent data from each ECU and cannot receive the engine-ECU data only.

TROUBLE JUDGEMENT CONDITIONS


M.U.T.-III judges the trouble when the periodically sent data from engine-ECU cannot be received.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Connector check: joint connector (CAN1), joint connector (CAN3), D-26 intermediate connector and engine-ECU connector
caution The strand end of the twist wire should be within 10 cm from the connector. For details refer to .
When checking the joint connector, ensure that its wiring harness side and its short pins are not damaged.

Q. Is the check result normal?
Go to Step 2.
Repair the defective connector. Replace the joint connector as necessary.

STEP 2. Resistance measurement at joint connector (CAN1) and D-26 intermediate connector.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Disconnect the joint connector (CAN1) and D-26 intermediate connector, and measure at the wiring harness side.
(2)Turn the ignition switch to the "LOCK" (OFF) position.
(3)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(4)Continuity between joint connector (CAN1) terminal No.11 and D-26 intermediate connector terminal No.19.
OK: Continuity (2 Ω or less)
(5)Continuity between joint connector (CAN1) terminal No.22 and D-26 intermediate connector terminal No.18.
OK: Continuity (2 Ω or less)
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?
<All the resistances measure 2 Ω or less> Go to Step 3 .
NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN1) and D-26 intermediate connector.

STEP 3. Resistance measurement at D-26 intermediate connector and joint connector (CAN3).
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Disconnect the D-26 intermediate connector and joint connector (CAN3), and measure at the wiring harness side.
(2)Turn the ignition switch to the "LOCK" (OFF) position.
(3)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(4)Continuity between D-26 intermediate connector terminal No.19 and joint connector (CAN3) terminal No.10.
OK: Continuity (2 Ω or less)
(5)Continuity between D-26 intermediate connector terminal No.18 and joint connector (CAN3) terminal No.21.
OK: Continuity (2 Ω or less)
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?
<All the resistances measure 2 Ω or less> Go to Step 4 .
NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between D-26 intermediate connector and joint connector (CAN3).

STEP 4. Resistance measurement at joint connector (CAN3) and engine-ECU connector.
caution A digital multimeter should be used. For details refer to .
caution The test wiring harness should be used. For details refer to .
(1)Disconnect the joint connector (CAN3) and the engine-ECU connector, and measure at the wiring harness side.
(2)Turn the ignition switch to the "LOCK" (OFF) position.
(3)
caution When measuring the resistance, disconnect the negative battery terminal. For details refer to .
Ensure that the negative battery terminal is disconnected.
(4)Continuity between joint connector (CAN3) terminal No.11 and engine-ECU connector terminal No.101 <4G64, 6B31>, 108 <4N15>.
OK: Continuity (2 Ω or less)
(5)Continuity between joint connector (CAN3) terminal No.22 and engine-ECU connector terminal No.102 <4G64, 6B31>, 109 <4N15>.
OK: Continuity (2 Ω or less)
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?
<All the resistances measure 2 Ω or less> Go to Step 5 .
NO : <Either or all of the resistances measure more than 2 Ω> Repair the wiring harness between joint connector (CAN3) and the engine-ECU.

STEP 5. Resistance measurement at engine-ECU connector.
caution A digital multimeter should be used. For details refer to .
(1)Remove the engine-ECU, and measure at the equipment side.
(2)Resistance between engine-ECU connector terminal Nos.101 and 102 <4G64, 6B31> or 108 and 109 <4N15>.
OK: 120 ± 20 Ω
caution Strictly observe the specified wiring harness repair procedure. For details refer to .

Q. Is the check result normal?
<Within 120 ± 20 Ω> Power supply to the engine-ECU may be suspected. Diagnose the fuel system (Refer to GROUP 13A - Troubleshooting <4G64>, GROUP 13B - Troubleshooting <6B31> or GROUP 13C - Troubleshooting <4N15>).
<Not within 120 ± 20 Ω> Replace the engine-ECU (Refer to GROUP 13A - Engine-ECU <4G64>, GROUP 13B - Engine-ECU <6B31> or GROUP 13C - Engine-ECU <4N15>).