Toyota Sienna Service Manual: Engine Control System Malfunction
DTC C1201/51 Engine Control System Malfunction
DESCRIPTION
If trouble occurs the engine control system, the ECM transmits the abnormality to the skid control ECU.
The skid control ECU set this DTC and the skid control ECU prohibits TRAC and
VSC control. 
INSPECTION PROCEDURE
1 CHECK ENGINE CONTROL SYSTEM
(a) Check if the normal system code is recorded for engine control system.
Result 
REPLACE ECM
Open or Short Circuit in ABS Solenoid Relay Circuit
DESCRIPTION
The ABS solenoid relay is built in the brake actuator assembly. This relay
supplies power to each ABS
solenoid. If the initial check is OK, after the ignition switch is turned to t ...
ECM Communication Circuit Malfunction
DTC C1203/53 ECM Communication Circuit Malfunction
DESCRIPTION
The circuit is used to send TRAC and VSC control information from the skid
control ECU to the ECM, and
engine control information fr ...
Other materials:
Problem symptoms table
Before inspecting the suspected areas listed in the table
below, check the fuse and relay.
Before inspecting the suspected areas listed in the table
below, check the DTCs.
Methods used to verify the cause of the problem are listed
in order of probability in the suspected are ...
Removal
1. REMOVE WINDSHIELD WIPER MOTOR ASSEMBLY
2. REMOVE FRONT OUTER COWL TOP PANEL SUBASSEMBLY
3. DRAIN ENGINE COOLANT
4. REMOVE V-BANK COVER SUB-ASSEMBLY
5. REMOVE NO. 2 AIR CLEANER INLET
6. REMOVE NO. 1 AIR CLEANER INLET
7. REMOVE AIR CLEANER CAP SUB-ASSEMBLY
Disconnect the 3 vacuum hoses.
...
Installation
1. INSTALL FRONT DOOR WINDOW FRAME MOULDING
Remove the tape from the front door window frame
moulding.
Clean the contact surface of the vehicle body with
white gasoline.
Clean the outer circumference of the front door
window frame moulding with white gasoline.
Apply new double-si ...
