Suzuki Wagon R Manual page 3047

6-2-148 ENGINE GENERAL INFORMATION AND DIAGNOSIS (M13 ENGINE)
DTC P1603 TCM Trouble Code Detected
DTC Detecting Condition
When ECM receives a trouble code from TCM, which indicates that some problem occurred in sensor circuits
and its calculated values used for operations such as idle speed control, engine power control, and so on by
TCM, ECM sets DTC P1603. (TCM outputs the trouble code to ECM when TCM can not compute the engine
control signal due to malfunctions of sensor circuits used for gear shift control.)
DTC Troubleshooting
Step
1 Was "Engine and Emission Control System
Check" performed?
2 DTC Check
Check DTC of TCM referring to "Diagnostic
Trouble Code (DTC) Check" in Section 7B1.
Is there any DTC(s)?
Action Yes
Go to Step 2.
Go to applicable DTC
troubleshooting.
No
Go to "Engine and Emis-
sion Control System
Check" in this section.
Substitute a known-good
ECM and recheck.