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:
Drive information
Average fuel economy*1, 2
Displays the average fuel consumption since the function was
reset.*3
Tank average fuel economy*1, 2
Displays the average fuel consumption since the vehicle was refueled.
Trip average fuel economy*1, 2
Displays the average fuel consumption since the engine wa ...
Steering Pad Switch Circuit
DESCRIPTION
This circuit sends an operation signal from the steering pad switch to the
radio receiver.
If there is an open in the circuit, the navigation system cannot be operated
using the steering pad switch.
If there is a short in the circuit, the resulting condition is the same as if ...
System description
1. CRUISE CONTROL SYSTEM
This system is controlled by the ECM, and is activated by
the throttle position sensor and motor. The ECM controls
the following functions: ON-OFF, - (COAST)/SET, +
(ACCEL)/RES (RESUME), CANCEL, vehicle speed
operation, motor output control, and overdrive control.
& ...
