Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Method
< Case #1 >
Judge as abnormal in engine off timer or power supply IC timer when the difference between wake-up 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.
Processed in order Step 1 through Step 3.
- Abnormality Judgment
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 | > 0.24 |
Time Needed for Diagnosis: Less than 1 second
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| (Power supply IC timer) - (Wake-up request time)/Wake-up request time | ≤ 0.24 |
Time Needed for Diagnosis: Less than 1 second
< Case #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.
Processed in order Step 1 through Step 3.
- Abnormality Judgment
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 | > 0.24 |
Time Needed for Diagnosis: Less than 1 second
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| {(Power supply IC timer) - (Wake-up request time)}/Wake-up request time | ≤ 0.24 |
Time Needed for Diagnosis: Less than 1 second
< Case #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.
- Abnormality Judgment
Judge as NG when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Wake-up time required by main CPU | Wake-up time sent back by sub CPU |
Time Needed for Diagnosis: 2 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Wake-up time required by main CPU | = Wake-up time sent back by sub CPU |
Time Needed for Diagnosis: Less than 1 second
< Case #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.
- Abnormality Judgment
Judge as NG when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Signal required by main CPU | Signal received from power supply IC |
Time Needed for Diagnosis: 2 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Signal required by main CPU | = Signal received from power supply IC |
Time Needed for Diagnosis: Less than 1 second
< Case #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.
- Abnormality Judgment
Judge as NG when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Operating status of main CPU | Operating status of sub CPU |
Time Needed for Diagnosis: 2 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Operating status of main CPU | = Operating status of sub CPU |
Time Needed for Diagnosis: Less than 1 second
< Case #6 >
Perform diagnosis for ignition switch status abnormality by detecting the difference in ignition switch status (ON or OFF) of main CPU and sub CPU.
Judge as NG when main CPU and sub CPU are different in ignition switch status.
- Abnormality Judgment
Judge as NG when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Ignition switch status of main CPU | Ignition switch status of sub CPU |
Time Needed for Diagnosis: 2 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Normality Judgment
Judge as OK when the following conditions are established.
| Malfunction Criteria | Threshold Value |
|---|---|
| Ignition switch status of main CPU | = Ignition switch status of sub CPU |
Time Needed for Diagnosis: Less than 1 second
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.