Inspection
Procedure 1: Communication between M.U.T.-III and SRS-ECU cannot be established.
OPERATION
The auxiliary battery power supply is supplied from the electric motor switch to SRS-ECU. To SRS-ECU, the power is supplied from two independent auxiliary battery power supplies
(fuse No. 15 and 21) having fuses. The system can be checked by connecting the M.U.T.-III to the diagnosis connector.
TROUBLE JUDGEMENT
If communication with all other systems is not possible, there is a high possibility that
there is a malfunction of the diagnosis circuit. If communication with only the SRS air bag
is not possible, an open circuit may be present in the SRS-ECU diagnosis output circuit or the
power supply circuit (including earth circuit).
PROBABLE CAUSES
Damaged wiring harness and connectors
Malfunction of SRS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Check that the M.U.T.-III can communicate with
the other systems.
Q.
Can the M.U.T.-III communicate with the other systems?
Go to Step 2.
Check the communication lines for short to earth and open circuit.
STEP 2. Resistance measurement at B-112 SRS-ECU conenctor and B-20
diagnosis connector
(1)Check that the negative auxiliary battery termina is disconnected. If connected,
disconnect the negative auxiliary battery termina.
(2)Disconnect B-112 SRS-ECU connector.
(3)
caution
Do not insert a test probe into the terminal from
its front side directly as the connector contact pressure may be weakened.
Take the following measurements at B-112 SRS-ECU connector and B-16 diagnosis conenctor.
Continuity between B-112 SRS-ECU connector terminal No.
38 and B-20 diagnosis conenctor terminal No. 7.
OK: Continuity (Less than 2 Ω)
Q.
Is the check result normal?
Go to Step 3
Repair the wiring harness between B-112 SRS-ECU connector terminal No. 38 and
B-20 diagnosis connector terminal No. 7.
STEP 3. Resistance measurement at B-112 SRS-ECU connector
(1)Check that the negative auxiliary battery terminal is disconnected. If the negative
auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-112 SRS-ECU connector.
(3)
caution
Do not insert a test probe into the terminal from
its front side directly as the connector contact pressure may be weakened.
Take the measurements below at the B-112 harness side connector.
Continuity between terminal No. 41 and body earth
OK: Continuity (less than 2 Ω)
note
Before the wiring harness check, check B-11 <LHD> and B-25 earth connector, and repair
if necessary.
Q.
Is the check result normal?
Go to Step 4
Repair the harness wires between the B-112 SRS-ECU connector terminal No.41 and
earth.
STEP 4. Voltage measurement at the B-112 SRS-ECU connector.
(1)Check that the negative auxiliary battery terminal is disconnected. If the negative
auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-112 SRS-ECU connector.
(3)Connect the negative auxiliary battery terminal.
(4)Electric motor switch to the "ON" position.
(5)
caution
Do not insert a test probe into the terminal from
its front side directly as the connector contact pressure may be weakened.
Take the measurements below at the B-112 harness side connector.
Voltage between terminal No. 37/43 and body
earth
OK: 9 V or more
(6)Disconnect the negative auxiliary battery terminal.
Q.
Is the check result normal?
Go to Step 5
Repair the wiring harness between B-112 SRS-ECU connector terminal No. 37/43
and the electric motor switch.
STEP 5. Check of the troubles
Q.
Is the communication between M.U.T.-III and SRS-ECU possible?
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with
Intermittent Malfunction ).
)
)
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Go to Step 2.
Check the communication lines for short to earth and open circuit.
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