10C-15 Immobilizer Control System:
DTC P1638: Immobilizer Information Mismatched
S7RS0BA304017
DTC Detecting Condition and Trouble Area
Troubleshooting
3 DTC check of BCM
1) Check BCM for DTC referring to “DTC Check in Section
10B”.
Is DTC U1073, U1100, and/or U1114 detected?
Go to applicable DTC
diag. flow.
Go to step 4.
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?
Go to Step 5. Repair circuit.
5 Replacement of BCM
1) Replace BCM with new one referring to “BCM (Included
in Junction Block Assembly) Removal and Installation in
Section 10B”.
2) Check ECM for DTC referring to “Diagnostic Trouble
Code (DTC) Check”.
Is DTC P1636 still detected?
Substitute a known-
good ECM and recheck.
BCM faulty.
Step Action Yes No
Detecting Condition Trouble Area
• 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.
• Use of the wrong ECM
• CAN communication circuits
•BCM
•ECM
Step Action Yes No
1 Was “Immobilizer Control System Check” performed? Go to Step 2. Go to “Immobilizer
Control System Check”.
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 “Diagnostic
Trouble Code (DTC) Check”.
Is DTC P1638 still detected?
Go to Step 3. Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”.
3 DTC check of ECM
1) Check ECM for DTC referring to “DTC Check in Section
1A”.
Is DTC P1674, P1675, P1678 and/or P1685 detected?
Go to applicable DTC
diag. flow.
Go to Step 4.
4 DTC check of BCM
1) Check BCM for DTC referring to “DTC Check in Section
10B”.
Is DTC U1073, U1100, U0155 and/or U1114 detected?
Go to applicable DTC
diag. flow.
Go to step 5.
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