Diagnostic Method

<Monitor 1> 

Judge as abnormal in engine off timer or power supply IC timer when the difference between wakeup request time and power supply IC timer exceeds the threshold value.

When the sub CPU is faulty, wake-up timing is either advancing or retarding compared with normal timing.

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Judge as NG when the following conditions are established.

Malfunction Criteria	Threshold Value
|(Power supply IC timer) - (Wake-up request time)|/Wake-up request time	More than 0.24

<Monitor 2> 

Judge as abnormal in engine off timer when the power supply IC timer exceeds the wake-up request time before wake up.

When case #1 is not performed, perform case #2.

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Judge as NG when the following conditions are established.

Malfunction Criteria	Threshold Value
{(Power supply IC timer) - (Wake-up request time)}/Wake-up request time	More than 0.24

<Monitor 3> 

Diagnose the communication error between main CPU and sub CPU.

Judge as NG when the wake-up time required from main CPU and the wake-up time received from sub CPU are different.

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Judge as NG when the following conditions are established.

Malfunction Criteria	Threshold Value
Wake-up time required by main CPU	Not equal to wake-up time sent back by sub CPU

<Monitor 4> 

Diagnose the communication error between main CPU and power supply IC.

Judge as NG when the signal required by main CPU and the signal received from power supply IC are different.

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Judge as NG when the following conditions are established.

Malfunction Criteria	Threshold Value
Signal required by main CPU	Not equal to signal received from power supply IC

<Monitor 5> 

On main CPU and sub CPU, there are two operation status: "normal mode" and "wake-up mode". Perform diagnosis for CPU operation status abnormality by detecting the difference in operating status of main CPU and sub CPU.

Judge as NG when main CPU and sub CPU is different in operating status.

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Judge as NG when the following conditions are established.

Malfunction Criteria	Threshold Value
Operating status of main CPU	Not equal to operating status of sub CPU

Time needed for diagnosis 

Monitor 1 and 2: Less than  1 s

Monitor 3 and 4:  2000 ms

Monitor 5:  3000 ms

Malfunction indicator light illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.