Self-Diagnosis
THREE FORMS OF SELF-DIAGNOSISInitial Diagnosis - Performed right after the engine starts until the ABS indicator light goes off.
Regular Diagnosis - Continuously performed (under some conditions) after the ABS indicator light goes off until the engine stops.
Individual Part/System Diagnosis - Diagnosis about a specific part/system under its operating conditions.
THE CENTRAL PROCESSING UNIT (CPU) - controls the following when it detects a problem during self-diagnosis:
- Turns the ABS indicator light ON.
- Turns the front and rear fail-safe relays off.
- Stops the ABS control.
- Stops the ABS pump. (The pump may work under some conditions.)
- After the DTC is stored in the control unit, the CPU stops self-diagnosis.
SELF DIAGNOSIS SYSTEM
The ABS control unit is equipped with a CPU and a sub CPU that check each other for problems.
The CPUs monitor the circuits of the system.
Self-diagnosis can be classified into two categories.
- Initial diagnosis: Performed right after the engine starts and until the ABS indicator goes OFF.
- Regular diagnosis: Performed right after the initial diagnosis until the ignition switch is turned OFF.
When a problem is detected by self-diagnosis, the system:
- Turns the fail-safe relay OFF
- Turns the solenoid valve OFF
- Turns the pump motor OFF
- Turns the ABS indicator ON
SELF DIAGNOSIS SYSTEM OPERATION
1. If the system is OK, the ABS indicator goes OFF two seconds after turning the ignition switch ON (II) without starting the engine, and then comes ON again and goes OFF after two seconds. This occurs because the ABS control unit is turned ON by the IG2 power source.
2. The ABS indicator comes ON when the ABS control unit detects a problem in the system. However, even though the system is operating properly, the ABS indicator will come ON, under the following conditions.
- Only drive wheels rotate
- One drive wheel is stuck
- Vehicle spin
- ABS continues to operate for a long time
- Signal disturbance
To determine the actual cause of problem, question the customer about the problem, taking these conditions into consideration.
3. When a problem is detected and the ABS indicator comes ON, there are cases when the indicator stays ON until the ignition switch is turned OFF, and cases when the indicator goes OFF automatically when the system returns to normal.
- For DTCs 61 and 62, the indicator goes OFF automatically when the system returns to normal.
- For all other codes, the indicator stays ON until the ignition switch is turned OFF.
4. For DTCs 12, 14, 16, 18, 21, 22, 23, 24, 51, 52 and 53, the indicator goes OFF when the vehicle is driven again and the system is OK after the ignition switch is turned from OFF to ON (II). However, if the DTC is erased, the Central Processing Unit (CPU) is reset and the indicator goes OFF right after the engine is started if the system is OK.
DIAGNOSTIC TROUBLE CODE STORAGE
1. If the CPU cannot be activated and the indicator comes ON, the Diagnostic Trouble Code (DTC) is not memorized.
2. The memory can hold any number of DTCs. However, when the same DTC is detected more than once, the later one is written over the old one. Therefore, when the same problem is detected repeatedly, it is memorized as one DTC.
3. The DTCs are indicated in the order of ascending number, not in the order they occur.
4. The DTCs are memorized in the EEPROM (non-volatile memory). Therefore, the memorized DTCs cannot be canceled by disconnecting the battery. Perform the specified procedures to erase the DTCs.
ACCESSING SELF DIAGNOSTIC TROUBLE CODES
The ABS control unit is connected to the 16P Data Link Connector.
The ABS CAN be diagnosed with the Honda PGM Tester.
The ALB Checker CANNOT be used with this system.
For air bleeding, and checking wheel sensor signals, use the Honda PGM Tester.
See the Honda PGM Tester user's manuals for specific operating instructions.
SELF DIAGNOSIS SYSTEM FUNCTION
Self-Diagnosis Table:
Operation Mode Table:
