Mitsubishi Grandis. Manual - part 996

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-36

STEP 5. Check the driver’s air bag module 
circuit. Voltage measurement at the SRS-ECU 
connector C-119.

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

DANGER

To prevent the air bag from deploying 
unintentionally, disconnect the clock spring 
connector C-309 to short the squib circuit.

(2) Disconnect the clock spring connector C-309.

(3) Turn the ignition switch to the "ON" position.

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 voltage between C-119 harness 

side connector terminals 36 and 37 <1st squib> 
or 33 and 34 <2nd squib> and body earth.

OK: 0 V

Q: Is the measured voltage within the specified 

range?

YES : 

Erase the diagnosis code memory, and 

check the diagnosis code. If diagnosis code 
B1403 <1st squib> or B1483 <2nd squib> 
sets, replace the SRS-ECU. (Refer to 

P.52B-223

). Then go to Step 7.

NO : 

Go to Step 6.

AC311438 AD

C-119 (Y)

Connector: C-119

Harness side
(front view)

AC310153AH

Connectors: C-309 <LHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC310183

AH

Connector: C-309 <RHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC301587

42

31

38

27

21

41

28

39

22

30

25

47

36

33

44

34

45

37

48

26

29

23

40

32

43

35

46

24

B

A

C-119 Harness side
connector (rear view)

<1st squib>

AE

AC308148

42

31

38

27

21

41

28

39

22

30

25

47

36

33

44

34

45

37

48

26

29

23

40

32

43

35

46

24

B

A

C-119 Harness side
connector (rear view)

<2nd squib>

AD

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-37

STEP 6. Check the harness for short circuit to 
power supply between SRS-ECU connector 
C-119 (terminal No.36 and 37 <1st squib> or 
terminal No.33 and 34 <2nd squib>) and clock 
spring connector C-309 (terminal No.3 and 4 <1st 
squib> or terminal No.1 and 2 <2nd squib>).

Q: Are harness wires between the SRS-ECU 

connector C-119 (terminal No.36 and 37 <1st 

squib> or terminal No.33 and 34 <2nd squib>) and 
clock spring connector C-309 (terminal No.3 and 4 
<1st squib> or terminal No.1 and 2 <2nd squib>) in 
good condition?

YES : 

Go to Step 7.

NO : 

Replace the harness wires between 
SRS-ECU connector C-119 and clock spring 
connector C-309. Then go to Step 7.

STEP 7. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code B1403 <1st squib> or B1483 

<2nd squib> set?

YES : 

Return to Step 1.

NO : 

The procedure is complete.

Code No.B1406: Front Impact Sensor (RH) System for Fault 1
Code No.B1416: Front Impact Sensor (LH) System for Fault 1

CAUTION

If diagnosis code B1406 or B1416 is set in the 
SRS-ECU, always diagnose the CAN main bus 
line.

DIAGNOSIS CODE SET CONDITIONS

These diagnosis codes are set if the following 
conditions are detected from the analogue G-sensor 

inside the front impact sensor output:

• Analogue G-sensor is not operating.

• Analogue G-sensor characteristics are abnormal.

• Analogue G-sensor output is abnormal.

AC311438 AD

C-119 (Y)

Connector: C-119

Harness side
(front view)

AC310153AH

Connectors: C-309 <LHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC310183

AH

Connector: C-309 <RHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-38

PROBABLE CAUSES

Malfunction of front impact sensor (RH) (for 
diagnosis code B1406) and front impact sensor (LH) 
(for diagnosis code B1416)

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

).

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

).

STEP 3. Check the front impact sensor. (MUT-III 
diagnosis code.)

Replace front impact sensor (RH) and front impact 
sensor (LH) (for diagnosis code B1416) (Refer to 

P.52B-220

).

Check the diagnosis code.

Q: Is either diagnosis code B1406 or B1416 set?

YES : 

Replace the SRS-ECU (Refer to 

P.52B-223

).

NO : 

The procedure is complete.

Code No.B1407: Front Impact Sensor (RH) Power Supply Circuit System

Wire colour code
B : Black     LG : Light green     G : Green     L : Blue     W : White     Y : Yellow     SB : Sky blue
BR : Brown     O : Orange     GR : Gray     R : Red     P : Pink     V : Violet

SRS-ECU

FRONT IMPACT
SENSOR (LH)

FRONT IMPACT
SENSOR (RH)

Front Impact Sensor Circuit

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-39

CAUTION

If diagnosis code B1407 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

OPERATION

The front impact sensor includes an analogue G 
sensor and CPU, etc. The CPU monitors the 
analogue G sensor output signal. If the CPU judges 
that the front air bags should be deployed, it sends a 
fire signal to the SRS-ECU to deploy the front air 
bags. In addition, the CPU diagnoses the internal 
components of the front impact sensor. If a 
malfunction occurs, it requests the SRS-ECU to set a 
diagnosis code.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code will set when the power supply 
voltage to the front impact sensor (RH) remains less 
than a predetermined value for five seconds. 
However, if the system returns to normal condition, 
code number B1407 will be erased automatically and 
the SRS warning lamp will go out.

PROBABLE CAUSES

• Damaged wiring harness or connectors

• Malfunction of the front impact sensor (RH)

• 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

).

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

).

STEP 3. Check the front impact sensor (RH) 
power supply circuit. Voltage measurement at the 
front impact sensor (RH) connector A-30.
(1) Disconnect the negative battery terminal.

(2) Disconnect front impact sensor (RH) connector 

A-30, and measure at the wiring harness side.

(3) Connect the negative battery terminal.
(4) Turn the ignition switch to the "ON" position.

CAUTION

Do not insert a test probe into the terminal from 
its front side directly, as the connector contact 
pressure may be weakened.
(5) Measure the voltage between A-30 harness side 

connector terminal 1 and the body earth.

OK: 9 V or more

Q: Is the check result normal?

YES : 

Replace the front impact sensor (RH). 

(Refer to 

P.52B-220

). Then go to Step 5.

NO : 

Go to Step 4.

AC311404 AB

A-30 (Y)

Connector: A-30

Harness side
(front view)

AC311097

A-30 Harness side
connector
(rear view)

AD