Isuzu N-Series. Manual - part 1195

SRS CONTROL SYSTEM 9C-27

Data Display
Move the connector or harness by hand. If the display
changes from fix to release, connection of connector is
faulty, pin tip length is uneven, or open or short circuit in
the harness exists where you have moved. Therefore,
repair is necessary. When asterisk mark (*) is displayed
in place of numeric display; Problem of Tech 2.
If asterisk mark (*) is found any of the data, PCMCIA
card must be version upgraded.

Snapshot (Graph Plotting)

• The snapshot can record the data list menu and

plot a graph.

• Utilizing this mode, reproduce and record the con-

ditions claimed by the customer to identify the en-
gine data fault.

• The stored data can be replayed with a domestic

power supply.

Programming

• Before replacing SRS control unit, be sure to

check/save the vehicle information. After replace-
ment, input it.

List of Diagnostic Trouble Code

Caution:

• Trouble codes No. 21, 25, 71 cannot be cleared.
• Code No. 12 indicates that the system is normal.

F0 : Read the DTC in the order of priority.

F1 : Clear the DTC.

Application menu

N9A0075E

Trouble code 

No.

Item to be detected

“SRS” warning lamp ON

14

Connector is half-connected

ON

21

Resistance of SRS airbag deployment circuit is large

ON

22

Resistance of SRS airbag deployment circuit is small

ON

24

SRS airbag deployment circuit is shorted to ground

ON

25

SRS airbag deployment circuit is shorted to ignition voltage

ON

26

SRS airbag deployment circuit is open

ON

51

SRS airbag deployment current had output

ON

53

Specific trouble when SRS airbag deployment current had output

ON

54

Deployment output by onboard deployment system communica-

tion

55

Vehicle type error

ON

61

Warning lamp circuit trouble

ON

63

Power supply voltage failure

ON

71

SRS control unit internal trouble

ON

9C-28 SRS CONTROL SYSTEM

DTC: 14  Connector is Half-connected

Outline

Description of Circuit
Turn the starter switch to “ON”. SRS control unit checks
the condition of half-connection detection terminal.

Condition when DTC is set
The half-connection detection terminals “a” and “b” are
not connected via connector.

Action to be taken
SRS control unit turns the warning lamp ON and set the
code 14.

Condition when DTC is cleared
Connector is connected completely, and the half-con-
nected terminal has continuity.

B

ACC

ON

ST

STARTER SWITCH

METER

AIRBAG

SRS CONTROL UNIT

DATA LINK CONNECTOR

16 15 14 13 12 11 10 9

8 7 6 5 4 3 2 1

0.5

B

0.5

GY

0.5

SB

0.5

GY

0.5

SB

16

4

19

15

18

7

8

20

6

5

0.85B

0.85B

0.5

B/R

0.5

B/R

0.5

W/R

0.5

B/R

0.5

B/R

0.5

W/R

0.5

B

1.25

B

2L

3
B/Y

2

14

3W/L

8B

3W/L

40A
KEY SW

10A
SRS

AIRBAG

SRS COIL

ASSEMBLY

1

2

2

1

0.5

Y

0.5

Y/B

3

10A
METER

0.5
B/Y

18

OFF

N9A0086E

SRS CONTROL SYSTEM 9C-29

Step

Action

Value

YES

NO

1

Has the “SRS system check” been per-
formed?

—

Go to Step2

Go to “SRS sys-

tem check”.

2

1. Turn the starter switch to OFF.
2. Check if the connector of the SRS control

unit is connected securely.

Is the connector of the SRS control unit con-
nected securely?

—

Go to Step3

Insert the SRS 

control unit con-

nector 

securely.Go to 

Step4

3

Temporarily disconnect the SRS control unit
connector, and check the half-connection
detection terminal for faulty such as bent and
dirt.

Is there any fault?

—

Replace either of 

the SRS control 

unit or SRS har-

ness whichever is 

faulty.Go to Step4

Go to Chart A 

SRS control unit 

function check.

4

1. Reconnect all the parts, and check that

those are installed properly.

2. Clear the DTC.

Is this step completed?

—

Check the repair.

Go to Step4

9C-30 SRS CONTROL SYSTEM

DTC: 21  Resistance of SRS Airbag Deployment Circuit is Large

Outline

Description of Circuit
Turn the starter switch to “ON”. SRS control unit per-
forms the tests to diagnose critical function fault inside
the SRS control unit. Upon completion of the tests, when
the results are pass, “Ignition” voltage and deployment
circuit voltage will be measured to check they are within
the normal range. Then, the SRS control unit performs
“Resistance measurement test”. SRS control unit flows
a minimal known amount of current between the termi-
nals “7” and “8”, and measures the voltage difference
between the two, and then calculates the combined re-
sistance in the SRS airbag, SRS coil assembly, SRS
airbag deployment circuit, and connector terminal con-
tact point.

Condition when DTC is Set
When combined resistance of SRS airbag, SRS coil as-
sembly, SRS airbag deployment circuit, and connector
terminal contact point exceeds the specified value. This
test is performed constantly after elapse of six seconds
from the “Ignition” voltage exceeds 10V.

Action to be Taken
SRS control unit turns the “SRS” warning lamp ON and
set the DTC 21.

Condition when DTC is Cleared
When the resistance goes back to less than specified
value.

Description of DTC Chart Test
Numbers below indicate step numbers in the diagnostic
chart.
2. This test is to check if the location of function fault is
in the SRS control unit.
3. This test is to check if the 2-pole connector (yellow)
located in the lower portion of steering column is proper-
ly connected.
4. This test is to check the 2-pole connector (yellow) ter-
minal located in the lower portion of steering column for
secure contact and/or corrosion.
5. This test is to check if the location of function fault is
up to the 2-pole connector (yellow) located in the lower
portion of steering column.
6. This test is to check the function fault is caused by
high resistance value in the wiring.
7. This test is to check if the location of function fault is
in the SRS coil assembly or SRS airbag.

SRS CONTROL UNIT

AIRBAG

SRS COIL

ASSEMBLY

1

2

2

1

0.5

Y

0.5

Y/B

8

7

N9A0076E