Mitsubishi Grandis. Manual - part 1036

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-196

CAUTION

If diagnosis code B1570, B1571, B1572, B1573,
B1574, B1575, B1576, B1577, B1578, B1579 or
B1581 are set in the SRS-ECU, always diagnose
the CAN bus lines.

OPERATION

According to the passenger’s air bag cut off switch
connecting position, the SRS-ECU judges the
deployment and non-deployment of passenger’s
(front) air bag.

DIAGNOSIS CODE SET CONDITIONS

Diagnosis code is set when the resistance between
input terminals of the passenger’s air bag cut off
switch in the SRS-ECU is without the standard value.
Cause of trouble in each diagnosis code is as
follows.

PROBABLE CAUSES

• Malfunction of the passenger’s air bag cut off

switch

• Damaged wiring harnesses or connectors

• Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. MUT-III CAN bus diagnostics
Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 3.

NO :

Repair the CAN bus line (Refer to GROUP
54D, Diagnosis

P.54D-16

). Then go to Step

STEP 2. Check whether the diagnosis code is
reset.
Check again if the diagnosis code is set.
(1) Erase the diagnosis code.
(2) Ignition: LOCK (OFF) position to ON
(3) On completion, check that the diagnosis code is

not reset.

Q: Is the diagnosis code set?

YES :

Go to Step 3.

NO :

There is an intermittent malfunction such as
poor engaged connector(s) or open circuit
(Refer to GROUP 00, How to Cope with
Intermittent Malfunction

P.00-5

Code No.

Symptom

B1570

Malfunction of passenger’s air bag cut off switch

B1571

Malfunction of the Normal/Close terminal or short circuit in its harness

B1572

Short to body earth in the Normal/Close terminal harness

B1573

Short to the power supply in the Normal/Close terminal harness

B1574

Malfunction of the Normal/Open terminal or short circuit in its harness

B1575

Short to body earth in the Normal/Open terminal harness

B1576

Short to the power supply in the Normal/Open terminal harness

B1577

Malfunction of the COM terminal or short circuit in its harness

B1578

Short to body earth in the COM terminal harness

B1579

Short to the power supply in the COM terminal harness

B1581

Detection of passenger’s air bag cut off switch misconecton

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-197

STEP 3. Connector check: C-107 passenger’s air
bag cut off switch connector

Q: Is the check result normal?

YES :

Go to Step 4.

NO :

Repair the defective connector.

STEP 4. Check the passenger’s air bag cut off
switch.
Refer to

P.52B-246

Q: Is the check result normal?

YES :

Go to Step 5.

NO :

Replace passenger’s air bag cut off switch.
(Refer to

P.52B-244

STEP 5. Check the passenger’s air bag cut off
switch circuit. Resistance measurement at
SRS-ECU connector C-119.

(1) Disconnect SRS-ECU connector C-119.

CAUTION

Do not insert a test probe into the terminal from
its front side directly as the connector contact
pressure may be weakened.
(2) Measure the resistance between terminal 29 and

terminal 35.

OK: Less than 10m

Ω

(3) Switch the passenger’s air bag cut off switch to

AC311374AB

Connector: C-107 <LHD>

Harness side
(front view)

AC311376AB

Connector: C-107 <RHD>

Harness side
(front view)

AC311438 AD

C-119 (Y)

Connector: C-119

Harness side
(front view)

AC313360

C-119 Harness side
connector (rear view)

AC313364

PASSENGER

AIRBAG

OFF

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-198

air bag OFF side.

CAUTION

Do not insert a test probe into the terminal from
its front side directly as the connector contact
pressure may be weakened.
(4) Measure the resistance between terminal 41 and

terminal 35.

OK: Less than 10m

Ω

Q: Is the check result normal?

YES :

Go to Step 6.

NO :

Repair the harness wires between
SRS-ECU connector C-119 (terminal No.29,
35 and 41) and passenger’s air bag cut off
switch connector C-107 (terminal No.1, 2
and 4).

STEP 6. Check whether the diagnosis code is
reset.

Q: Is diagnosis code B1570, B1571, B1572, B1573,

B1574, B1575, B1576, B1577, B1578, B1579 or
B1581 set?

YES :

Replace the SRS-ECU. (Refer to

P.52B-223

NO :

An intermittent malfunction is suspected
(Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points

P.00-5

Code No.U1073: Bus Off

CAUTION

If diagnosis code U1073 is set in the SRS-ECU,
diagnose the CAN main bus line.

CAUTION

Whenever the ECU is replaced, ensure that the
input and output signal circuits are normal.

TROUBLE JUDGMENT

Diagnosis code No.U1073 will be stored when the
SRS-ECU ceases CAN communication (bus off) and
then resumes the communication by turning the
ignition switch to the "LOCK" (OFF) position

COMMENTS ON TROUBLE SYMPTOM

The wiring harness wire or connectors may have
loose, corroded, or damage terminals, or terminals
pushed back in the connector, or the SRS-ECU may
be defective.

PROBABLE CAUSES

• Defective connector(s) or wiring harness

• Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. MUT-III CAN bus diagnostics
Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES :

Go to Step 2.

NO :

Repair the CAN bus line (Refer to GROUP
54D, Diagnosis

P.54D-16

not reset.