Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1700

9J1–11

RESTRAINT CONTROL SYSTEM

System Schematic

D09R100002

SRS Diagnostic System Check

The diagnostic procedures used in this section are
designed to find and repair Supplemental Restraint
System (SRS) malfunctions.   To get the best results, it is
important to use the diagnostic charts and follow the
sequence listed below:
A. Perform the “SRS Diagnostic System Check.”

The “SRS Diagnostic System Check” must be the
starting point of any SRS diagnostics.   The “SRS
Diagnostic System Check” checks for proper “AIR
BAG” warning lamp operation,  the ability of the
Sensing and Diagnostic Module (SDM) to
communicate through the “Serial Data” line and
whether SRS diagnostic trouble codes exist.

B. Refer to the proper diagnostic chart as directed by the

“SRS Diagnostic System Check.”
The “SRS Diagnostic System Check” will lead you to
the correct chart to diagnose any SRS malfunctions.
 Bypassing these procedures may result in extended

diagnostic time, incorrect diagnosis and incorrect
parts replacement.

C. Repeat the “SRS Diagnostic System Check” after any

repair or diagnostic procedures have been
performed.
Performing the “SRS Diagnostic System Check” after
all repair or diagnostic procedures will ensure that the
repair  has been made correctly and that no other
malfunctions exist

Circuit Description

When the ignition switch is first turned “ON”, “ignition 1”
voltage is applied from the “SRS” fuse to the SDM at the
“ignition 1” input terminals “12”.  The SDM responds by
flashing the “AIR BAG” warning lamp seven  times while
performing tests on the SRS.

RESTRAINT CONTROL SYSTEM

9J1–12

Notes On System Check Chart:

Number(s) below refer to step number(s) on the
“Supplemental Restraint System Diagnostic System
Check” chart.
1. The “AIR BAG” warning lamp should flash seven

times after ignition is first turned “ON.”

2. After the “AIR BAG” warning lamp flashes seven

times, it should turn “OFF.”

3. Improper operation of the “AIR BAG” warning lamp

is indicated.  This test differentiates a warning lamp
stays “ON” condition from a warning lamp does not
come “ON” condition. 

4. This test checks for the proper operation of the

“Serial Data” line.  This test will also determine
whether history diagnostic trouble codes are stored
and, if so, identify them.

5. This test checks for proper operation of the “Serial

Data” line.  This test will also identify the stored
diagnostic trouble codes and whether they are
current or history.

Diagnostic Aids:

The order in which diagnostic trouble codes are
diagnosed is very important.  Failure to diagnose the
diagnostic trouble codes in the order specified may result
in extended diagnostic time, incorrect diagnosis and
incorrect parts Replacement.

9J1–13

RESTRAINT CONTROL SYSTEM

SRS Diagnostic System Check

Step

Action

Yes

No

1

Note the “AIR BAG” warning lamp when ignition switch is turned
“ON.”

Does the “AIR BAG” warning lamp flash seven (7) times?

Go to 

Step 2 

Go to 

Step 3

2

Note the “AIR BAG” warning lamp after it flashed 7 times.

Does the “AIR BAG” warning lamp go “OFF”?

Go to 

Step 4

Go to 

Step 5

3

Note the “AIR BAG” warning lamp when ignition switch is turned
“ON.”

Does the “AIR BAG” warning lamp come “ON” steady?

Go to 

Chart B

Go to 

Chart C.

4

1. Ignition switch “OFF.”
2. Connect a scan tool to data link connector.
3. Follow direction given in the scan tool instruction manual.
4. Ignition switch “ON.”
5. Request the SRS diagnostic trouble code display recode all

history diagnostic trouble code(s) specify as such, on repair
order.

Is diagnostic trouble code(s) displayed?

Ignition switch

“OFF.”

When DTC 71 is

set, go to DTC 71

chart.

For all other

history codes

refer to

“Diagnostics

Aids” for that

specific DTC.

A history DTC

indicates the

malfunction has

been repaired or

is intermittent.

SRS is functional

and free of

malfunctions, no

further diagnosis

is required.

If scan tool

indicates “No

Data Received,”

refer to chassis

electrical section.

5

1. Ignition switch “OFF.”
2. Connect a scan tool to data link connector.
3. Follow directions as given in the scan tool instruction manual.
4. Ignition switch “ON.”
5. Request the SRS diagnostic trouble code display, recode all

diagnostic trouble code(s), specifying as current or history on
repair order.

Is diagnostic trouble code(s) displayed?

Ignition switch

“OFF.”

When DTC 53 is

set, go to DTC 53

chart.

When DTC 51 is

set, go to DTC 51

chart.

When DTC 19 is

set, go to DTC 19

chart.

When DTC 25 is

set, go to DTC 25

chart.

Diagnose

remaining current

DTCs from

lowest to

highest.When

only history DTCs

exist, Refer to

“Diagnostics

Aids” for that

specific DTC.

A history DTC

indicates the

malfunction has

been repaired or

is intermittent.

If scan tool

indicates “No

Data Received,”

refer to chassis

electrical section.

RESTRAINT CONTROL SYSTEM

9J1–14

Chart A  SDM Integrity Check

D09R100002

Circuit Description:

When the Sensing and Diagnostic Module (SDM)
recognizes “ignition 1” voltage, applied to terminals “12”,
is greater than 9  volts, the “AIR BAG” warning lamp is
flashed 7 times to verify operation.  At this time the  SDM
performs “Turn–ON” tests followed by “Continuous
Monitoring” tests.  When a malfunction  is detected, the
SDM sets a current diagnostic trouble code and
illuminates the “AIR BAG”  warning lamp. The SDM will
clear current diagnostic trouble codes and move them to
a history  file when the malfunction is no longer detected
and/or the ignition switch is cycled, except  for Diagnostic
Trouble Codes (DTCs) 51, 53 and 71.  DTC 71 can only be
cleared using a scan tool “Clear Codes”  command in
case that the malfunction on DTC 71 has been solved and
no DTCs 51 and 53 were remained.  DTCs 51, 53 and 71
can not be cleared after a “Clear Codes” command is
issued.

Chart Test Description:

Number(s) below refer to step number(s) on the
diagnostic chart:
1. This test confirms a current malfunction.  If no

current  malfunction is occurring (history DTC set)
the “Diagnostic Aids” for the appropriate  diagnostic
trouble code should be referenced.  The SDM
should not be replaced for a history  diagnostic
trouble code.

2. This test checks for a malfunction introduced into the

SRS during  the diagnostic process.  It is extremely
unlikely that a malfunctioning SDM would cause a
new malfunction to occur during the diagnostic
process.

3. When all circuitry outside the SDM has been found

to operate properly,  as indicated by the appropriate
diagnostic chart, then and only then should the SDM
be  replaced.