Subaru 2009 IMPREZA Service Manual page 869

Diagnostic Trouble Code (DTC) Detecting Criteria
BZ:DTC P0604 INTERNAL CONTROL MODULE RANDOM ACCESS MEMORY
(RAM) ERROR
1. OUTLINE OF DIAGNOSIS
Detect the malfunction of microcomputer (RAM).
When there is a problem in the main CPU normal RAM, or the sub CPU normal RAM, judge as NG. Judge
as OK when both are operating properly.
If it is possible to write data to the whole area of RAM in the initial routine, and is possible to read the same
data, it is judged as OK, and if not, NG.
2. ENABLE CONDITIONS
Secondary Parameters
None
Diagnosis with the initial routine.
3. GENERAL DRIVING CYCLE
Perform the diagnosis as soon as the ignition switch is turned to ON.
4. DIAGNOSTIC METHOD
Abnormality Judgement
Judge as NG if the criteria below are met.
Judgement Value
Malfunction Criteria
Main CPU normal RAM abnormal
Write 5AA5A55A and then read. (Whole
area of RAM)
Write A55A5AA5 and then read. (Whole
area of RAM)
Sub CPU normal RAM abnormal
Write 5AA5 and then read. (Whole area
of RAM)
Write A55A and then read. (Whole area
of RAM)
Time Needed for Diagnosis: Undetermined
Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.
Normality Judgement
Judge as OK and clear the NG when the malfunction criteria below are met.
Judgement Value
Malfunction Criteria
Main CPU normal RAM abnormal
Write 5AA5A55A and then read. (Whole
area of RAM)
And write A55A5AA5 and then read.
(Whole area of RAM)
Sub CPU normal RAM abnormal
Write 5AA5 and then read. (Whole area
of RAM)
And write A55A and then read. (Whole
area of RAM)
Enable Condition
Threshold Value
5AA5A55A cannot be
read.
A55A5AA5 cannot be
read.
5AA5 cannot be read.
A55A cannot be read.
Threshold Value
5AA5A55A can be
read.
A55A5AA5 can be
read.
5AA5 can be read.
A55A can be read.
GD(H4SO)-145
GENERAL DESCRIPTION