Isuzu N-Series. Manual - part 1196

SRS CONTROL SYSTEM 9C-31

Point of Diagnosis
In the situations that the trouble display appears inter-
mittently, it may be caused by improper connection be-
tween 2-pole connector terminals “1” and “2” of SRS coil
located in the lower portion of steering column, between
2-pole connector terminals “1” and “2” of SRS airbag lo-
cated in the upper portion of steering column, between
SRS control unit terminals “7” and “8”, or between the
wire and terminal in SRS airbag deployment circuit.

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. When measurement is required in this

chart, use 5-8840-0366-0 DMM and ap-
propriate terminal adapter in 5-8840-
0385-0 Connector test adapter kit.

2. Using the data list function of Tech 2,

read the resistance in airbag deployment
circuit and record it.

Does the resistance in airbag deployment cir-
cuit exceed specified value?

7.2

Ω

Go to Step3

Go to Chart A 

SRS control unit 

function check.

3

1. Turn the starter switch to OFF.
2. Check the 2-pole connector (yellow) of

SRS coil located in the lower portion of
steering column for proper connection.

Is the 2-pole connector connected properly?

—

Go to Step4

Connect the 2-

pole connector of 

SRS coil assem-

bly properly.Go to 

Step8

4

1. Remove the 2-pole connector (yellow) of

SRS coil located in the lower portion of
steering column for inspection.

2. If it is normal, reconnect the 2-pole con-

nector of SRS coil assembly properly.

3. Turn the starter switch to ON.

Is DTC 21 detected as current trouble?

—

Go to Step5

Go to Step8

5

1. Turn the starter switch to OFF.
2. Remove the 2-pole connector (yellow) of

SRS coil assembly located in the lower
portion of steering column.

3. Connect the 5-8840-2421-0 SRS substi-

tute load and an appropriate terminal
adapter in the 5-8840-0385-0 Connector
test adapter kit to the SRS harness side
connector which connects to SRS coil as-
sembly.

4. Turn the starter switch to ON.

Is DTC 21 detected as current trouble?

—

Go to Step6

Go to Step7

9C-32 SRS CONTROL SYSTEM

6

1. Turn the starter switch to OFF.
2. Resistance of all circuit in the driver’s

airbag deployment circuit is increasing.

3. Inspect the SRS airbag deployment cir-

cuit and SRS control unit connector ter-
minals “7” and “8”, and use high-
resolution resistance meter mode of
DMM to detect the cause.

Is the trouble detected?

—

Replace the SRS 

harness.Go to 

Step8

Go to Chart A 

SRS control unit 

function check.

7

1. Turn the starter switch to OFF.
2. Remove the 5-8840-2421-0 SRS substi-

tute load from SRS coil assembly har-
ness connector.

3. Connect the 5-8840-2421-0 SRS substi-

tute load to the upper portion of steering
column.

4. Reconnect the SRS coil assembly har-

ness connector to the lower portion of
steering column.

5. Turn the starter switch to ON.

Is DTC 21 detected as current trouble?

—

Turn the starter 

switch to OFF. 

Replace the SRS 

coil assembly by 

referring to “SRS 

Coil Assembly” in 

SRS section. Go 

to Step8

Turn the starter 

switch to OFF. 

Replace the SRS 

airbag. Go to 

Step8

8

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 Step8

Step

Action

Value

YES

NO

SRS CONTROL SYSTEM 9C-33

DTC: 22  Resistance of SRS Airbag Deployment Circuit is Small

Outline

Description of Circuit
Turn the starter switch to “ON”. SRS control unit per-
forms the tests to diagnose critical function fault in the
SRS control unit. Upon completion of the tests, when the
results are pass, “Ignition” voltage and deployment cir-
cuit 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 monitors the voltage difference be-
tween the two, and then calculates the combined
resistance 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 is less than the specified value.
This test is performed constantly after elapse of six sec-
onds from the “Ignition” voltage exceeds 10V.

Action to be Taken
Airbag SRS control unit turns the “SRS” warning lamp
ON and set the DTC 22.

Condition when DTC is Cleared
When the resistance goes back to more than the speci-
fied 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 if the shorting clip of 2-pole con-
nector (yellow) operates properly.
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 low
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.

Point of Diagnosis
In the situations that the trouble appears intermittently, it
may be caused by short circuit in the SRS airbag de-
ployment circuit, or function fault in the SRS airbag or in
the shorting clip of SRS coil assembly which requires
parts replacement.

SRS CONTROL UNIT

AIRBAG

SRS COIL

ASSEMBLY

1

2

2

1

0.5

Y

0.5

Y/B

8

7

N9A0076E

9C-34 SRS CONTROL SYSTEM

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. When measurement is required in this

chart, use 5-8840-0366-0 DMM and ap-
propriate terminal adapter in 5-8840-
0385-0 Connector test adapter kit.

2. Using the data list function of Tech 2,

read the resistance in SRS airbag de-
ployment circuit and record it.

Is the resistance in airbag deployment circuit
less than the specified value?

2.1

Ω

Go to Step3

Go to Chart A 

SRS control unit 

function check.

3

1. Turn the starter switch to OFF.
2. Check the 2-pole connector (yellow) of

SRS coil assembly located in the lower
portion of steering column for proper con-
nection.

Is the 2-pole connector connected properly?

—

Go to Step4

Connect the 2-

pole connector of 

SRS coil assem-

bly properly.Go to 

Step8

4

1. Remove the 2-pole connector (yellow) of

SRS coil assembly located in the lower
portion of steering column for inspection.

2. If it is normal, reconnect the 2-pole con-

nector of SRS coil assembly properly.

3. Turn the starter switch to ON.

Is DTC 22 detected as current trouble?

—

Go to Step5

Go to Step8

5

1. Turn the starter switch to OFF.
2. Remove the 2-pole connector (yellow) of

SRS coil assembly located in the lower
portion of steering column.

3. Connect the 5-8840-2421-0 SRS substi-

tute load and an appropriate terminal
adapter in 5-8840-0385-0 Connector test
adapter kit to the SRS harness side con-
nector which connects to SRS coil as-
sembly.

4. Turn the starter switch to ON.

Is DTC 22 detected as current trouble?

—

Go to Step6

Go to Step7

6

1. Turn the starter switch to OFF.
2. Resistance of all circuit in the SRS airbag

deployment circuit is decreasing.

3. Inspect the SRS airbag deployment cir-

cuit and SRS control unit connector ter-
minals “7” and “8”, and use high-
resolution resistance meter mode of 5-
8840-0366-0 DMM to detect the cause.

Is the trouble detected?

—

Replace the SRS 

harness.Go to 

Step8

Go to Chart A 

SRS control unit 

function check.