Toyota Sienna Service Manual: Internal Control Module Random Access Memory (RAM) Error
DESCRIPTION
The ECM continuously monitors its own internal memory status, internal circuits, and output signals transmitted to the throttle actuator. This self-check ensures that the ECM is functioning properly. If any malfunction is detected, the ECM sets the appropriate DTC and illuminates the MIL.
The ECM memory status is diagnosed by internal mirroring of the main CPU and the sub CPU to detect Random Access Memory (RAM) errors. The two CPUs also perform continuous mutual monitoring. The ECM illuminates the MIL and sets a DTC if: 1) outputs from the two CPUs are different or deviate from the standards, 2) the signals sent to the throttle actuator deviate from the standards, 3) a malfunction is found in the throttle actuator supply voltage, and 4) any other ECM malfunction is found.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
INSPECTION PROCEDURE
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
1 CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0604)
(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch to the ON position.
(c) Turn the tester on.
(d) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
(e) Read DTCs.
Result 
REPLACE ECM
System Voltage
MONITOR DESCRIPTION
The battery supplies electricity to the ECM even when the ignition switch is
off. This power allows the
ECM to store data such as DTC history, freeze frame data and fuel tr ...
ECM / PCM Processor
DESCRIPTION
The ECM continuously monitors its internal processors (CPUs), A/F sensor
transistors and heated oxygen
sensor (HO2S) transistors. This self-check ensures that the ECM is functionin ...
Other materials:
System Too
DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic
injection time. The fuel trim
consists of both the short-term and long-term fuel trims.
The short-term fuel trim is fuel compensation that is used to constantly
maintain the air-fuel ratio at
stoich ...
Memory recall function
Each electronic key can be registered to recall your preferred driving
position.
Registering procedure
Record your driving position to button “1” or “2” before performing
the following:
Carry only the key you want to register, and then close the driver’s
door.
If 2 or more keys ar ...
Linked mirror function when reversing (if equipped)
When the mirror select switch is in the L or R position, the outside rear
view mirrors will automatically angle downwards when the vehicle is
reversing in order to give a better view of the ground.
To disable this function, move the mirror select switch to the neutral
position (between L and R ...
