Dtc P1638: Immobilizer Information Mismatched - Suzuki SX4 Service Manual

Step
4 CAN communication circuit check
1) Disconnect connectors from ECM, BCM and ABS
control module.
2) Check CAN communication circuit for open, short and
high resistance.
• Between ECM and ABS control module
• Between BCM and ABS control module
Is each CAN communication circuit in good condition?
5 Replacement of BCM
1) Replace BCM with new one referring to "BCM (Included
in Junction Block) Removal and Installation in Section
10B".
2) Check ECM for DTC referring to "DTC Check".
Is DTC P1636 still detected?

DTC P1638: Immobilizer Information Mismatched

Wiring Diagram
Refer to "Immobilizer Control System Wiring Circuit Diagram".
Detecting Condition and Trouble Area
Detecting Condition
• The immobilizer control system information in ECM and
the one in BCM does not match.
• The registration of the immobilizer control system
information in ECM is failed.
Troubleshooting
Step
1 Was "Immobilizer Control System Check" performed?
2 DTC confirmation
1) Disconnect negative (–) cable from battery for more than
5 seconds.
2) Connect negative (–) cable to battery.
3) Check if any DTC is detected referring to "DTC Check".
Is DTC P1638 still detected?
3 ECM specification check
1) Check ECM part number to see if ECM is applicable to
the vehicle in service.
Is a correct ECM used for the vehicle in service?
4 DTC check of ECM
1) Check ECM for DTC referring to "DTC Check in Section
1A".
Is DTC U0073, U0101, U0121 and/or U0140 detected?
Action
Action
Immobilizer Control System:
Yes
Go to Step 5.
Substitute a known-
good ECM and recheck.
Trouble Area
• Use of the wrong ECM
• CAN communication circuit
• Keyless start control module (if equipped)
• Combination meter
• TCM (A/T model)
• 4WD control module (if equipped)
• ABS control module
• BCM
• ECM
Yes
Go to Step 2.
Go to Step 3.
Go to Step 4.
Go to applicable DTC
diag. flow.
10C-16
No
Repair circuit.
BCM faulty.
S7RW0AA304017
No
Go to "Immobilizer
Control System Check".
Intermittent trouble.
Check for intermittent
referring to "Intermittent
and Poor Connection
Inspection in Section
00".
Replace ECM with the
correct one and recheck
if DTC P1638 is still
detected by ECM.
Go to Step 5.