2007 MITSUBISHI LANCER EVOLUTION ECU

SRS -Troubleshooting52B-12
Code No.21 Driver’s air bag module (squib) systemPossible Cause
This code is output when short circuit occurs between terminals of the
SRS-ECU driver’s air bag module (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DConnector engagement faulty or short bar faulty*
DShort circuit in the clock spring
DShort circuit between terminals of the driver’s air
bag module (squib) circuit
DFaulty connector
DSRS-ECU inoperable
NOTE:
(1) *: The connector of the squib circuit contains a short bar (short-circuiting the positive (+) cable and
the negative ( - ) cable to avoid an erroneous deployment caused by static electricity when a connector
is not connected). Thus, when a connector is connected, the short bar may not be released due
to improper engagement of the connector or faulty connector as shown in the illustration below.
Disconnect the connector as shown in the illustration below, then reconnect it. Check that a diagnosis
code is output again after erasing the memory. If the diagnosis code is not output, the above-mentioned
code is output due to improper engagement of the connector.
C-204C-207
SRS-ECU
Clock spring
Driver’s air bag module C-21
(2) Two different types of driver’s air bag modules by model are featured. Thus, two types of air bag
module by model are described in the following flowchart.
RS: Steering wheel and air bag module separate type
RS-II: Steering wheel and air bag module incorporate type

SRS -Troubleshooting52B-13

NG
spring>
Measure at the SRS-ECU connector C - 21.
DDisconnect the SRS-ECU connector C-21.
DRelease the the clock spring connector C-204.
Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 11, 12 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 11 and 12
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuity
Check connector:C-21, C-204
MUT-II self-diag code
DRelease the clock spring connector (2 - pin) C-204.
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DInsert the resistor harness
(MB991866) behind the harness side connector C-204.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.21 output?
Resistor harness
(MB991866)
C - 204 clock spring
harness side connector
YES Dummy resistor
(MB991865)
resistance (3Ω)
Check the clock spring (Refer to P.52B-59.)
NOYES
Replace the clock spring.Replace the driver’s air bag module
(squib).NO
Check the harness between the clock spring and the
SRS-ECU, and repair if necessary.
Check the trouble
symptoms.Correct
OK
NG NG
Replace the SRS-ECU.
OK
Figure A
Terminal
Short bar
Front view of SRS-ECU
connector C-21
(harness side)
Cable band
and etc.Section
A-A
4 mm or more
A
AConnector C-21

SRS -Troubleshooting52B-15
OKNG
spring>
Measure at the SRS-ECU connector C - 21 .
DDisconnect the SRS-ECU connector C-21.
DRelease the the clock spring connector C-204.
Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 11, 12 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 11 and 12
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuity
Replace the SRS-ECU.
Figure A
Terminal
Short bar
Front view of SRS-ECU
connector C-21
(harness side)
Cable band and etc.Section
A-A
4 mm or more
A
A
Connector C-21
YES
From Previous Page
Check the harness between the clock spring and the
SRS-ECU, and repair if necessary.
Check connector: C - 21, C-204
Check the trouble
symptoms.
NG
CorrectOK
NG

SRS -Troubleshooting52B-16
Code No.22 Driver’s air bag module (squib) systemPossible Cause
This code is output when open circuit occurs in the SRS-ECU driver’s air bag
module (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DOpen in the clock spring
DHalf open in the circuit due to improper neutral
positioning of the clock spring
DOpen in the driver’s air bag module (squib) circuit
DDriver’s air bag module (squib) connector falling
out
DConnector improper contact
DSRS-ECU inoperable
NOTE:
Two different types of driver’s air bag modules by model are featured. Thus, two types of air bag module
by model are described in the following flowchart.
RS: Steering wheel and air bag module separate type
RS-II: Steering wheel and air bag module incorporate type

SRS -Troubleshooting52B-17

spring>
Measure at the SRS-ECU connector C-21 and the clock
spring connector C-204.
DDisconnect the SRS-ECU connector C-21 and the clock
spring connector C-204 and measure at the harness side.
DContinuity check between the following terminals
Connector C-21 Connector C-204
11 – 2
12 – 1
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:Continuity (2Ωor less)
NG
Correct
Check connector:C-21, C-204
OK
Check the trouble
symptoms.
NG
Check the harness between the clock spring and the
SRS-ECU, and repair if necessary. NG
Connector C-21Connector C-204
MUT-II self-diag code
DRelease the clock spring connector (2 - pin) C-204.
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DInsert the resistor harness
(MB991866) behind the harness side connector C-204.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.22 output?
YES
Check the clock spring (Refer to P.52B-59.)
NOYES
Replace the clock spring.Replace the driver’s air bag module
(squib).NO
Replace the SRS-ECU.
OK Resistor harness
(MB991866)
Clock spring harness
side connector C - 204 Dummy resistor
(MB991865)
resistance (3Ω)

SRS -Troubleshooting52B-19
spring>
Measure at the C-21 SRS-ECU connector and C-204 clock
spring connector.
DDisconnect the SRS-ECU connector C-21 and the clock
spring connector C-204 and measure at the harness side.
DContinuity check between the following terminals
C-21 connector C-204 connector
11 – 2
12 – 1
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:Continuity (2Ωor less)
NG
Correct
Check connector:C-21, C-204
OK
Check the trouble
symptoms.
NG
Check the harness between the clock spring and the
SRS-ECU, and repair if necessary.
YES
From Previous Page
NG
Connector C-21Connector C-204
Replace the SRS-ECU.
OK

SRS -Troubleshooting52B-20
Code No.24 Front passenger’s air bag module (squib)
systemPossible Cause
This code is output when short circuit occurs between terminals of the
SRS-ECU front passenger’s air bag (squib) circuit.
However, SRS warning lamp goes out when a normal operation is resumed
(diagnosis code is not cleared.)DConnector engagement faulty or short bar faulty*
DShort circuit between terminals of the front
passenger’s air bag (squib) circuit
DFaulty connector
DSRS-ECU inoperable
NOTE:
*: The connector of the squib circuit contains a short bar (short-circuiting the positive (+) cable and the
negative ( - ) cable to avoid an erroneous deployment caused by static electricity when a connector is
not connected). Thus, when a connector is connected, the short bar may not be released due to improper
engagement of the connector or faulty connector as shown in the illustration below. Disconnect the connector
as shown in the illustration below, then reconnect it. Check that a diagnosis code is output again after
erasing the memory. If the diagnosis code is not output, the above-mentioned code is output due to
improper engagement of the connector.
C-21
SRS-ECUC-109
Front passenger’s air bag module

SRS -Troubleshooting52B-21
OK
passenger’s air bag module>
Measure at the C-21 SRS-ECU connector.
DDisconnect the SRS-ECU connector C-21.
DDisconnect the front passenger’s air bag module connector
C-109.
Caution
Disconnect the connector and short-circuit the squib
circuit before releasing the short bar of the SRS-ECU
connector in the following operation.
DCable bands between terminals 9, 10 and the short bar
(width:3 mm, thickness:0.5 mm) between terminals 11 and
12 and the short bar, and release the short bar.
(See Figure A.)
Caution
As the short bar may not be releasable if inserted
insufficiently, insert more than 4 mm.
DMeasure at the harness side
DContinuity check between terminals 9 and 10
Caution
Do not directly insert a probe or other devices at the
front of the connector to avoid a possible decrease in
the contact pressure.
OK:No continuity
YESNO
Replace the front passenger’s seat air bag module (squib).
Resistor harness
(MB991866) Dummy resistor
(MB991865)
resistance (3Ω)
Instrumental panel
wiring harness
Front passenger’s air bag
module connector
MUT-II self-diag code
DConnect the dummy resistor (MB991865) to the resistor harness
(MB991866).
DDisconnect the front passenger’s air bag module connector C-109
and insert the resistor harness (MB991866) behind the harness side
connector.
Caution
Do not directly insert a probe or other devices at the front of the
connector to avoid a possible decrease in the contact pressure.
DConnect the negative ( - ) terminal of the battery
DCheck the diagnosis code again after erasing the memory.
Is code No.24 output?
Check the trouble
symptoms.
NG
Check the harness between the front passenger’s air bag
module and the SRS-ECU, and repair if necessary. NG
YESNG
Correct
Check connector:C-21, C-109
Connector C-21
Figure A
Terminal
Short bar
Front view of C-21
SRS-ECU connector
(harness side).
Cable band
and etc.Section
A-A
4 mm or more
A
A
Replace the SRS-ECU.