Description of On-Board Diagnostics

General Troubleshooting Information
System Indicators
- If the system is OK, the ABS indicator goes off 2 seconds after turning the ignition switch ON (II).
- The ABS indicator or VSA system indicator comes on when the VSA control unit detects a problem in the system.
- The ABS indicator or VSA system indicator will also come on under these conditions, even though the system is operating properly:
- The vehicle goes into a spin
- The ABS continues to operate for a long time
- The vehicle is subjected to an electrical signal disturbance
- If the VSA off switch is pushed, or if there is a fault in one or more of these components, only the VSA system indicator comes on:
- Yaw rate sensor, lateral acceleration sensor, steering angle sensor, apply/dump solenoids, modulator unit, PGM-FI communication, neutral position, TCS control valve sensor, TCS control valve actuator.
- Heated oxygen sensor, manifold absolute pressure sensor, crankshaft position sensor, engine coolant temperature sensor, throttle position sensor, top dead center sensor, top dead center sensor 2, intake air temperature sensor, exhaust gas recirculation, barometric pressure, idle air control valve, VTEC pressure switch, knock sensor, fuel supply system, automatic transmission, misfire detection system of the PGM-FI system.
- The VSA activation indicator will flash when only the drive wheels rotate, one of the drive wheels is stuck, or if the system detects an understeer or oversteer condition.
To determine the actual cause of the problem, question the customer about the problem, taking these conditions into consideration.
- When a problem is detected, and the ABS or VSA system 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.
- For DTCs 12, 14, 16, 18, 21, 22, 23, 24, 41, 42, 43, 44, 51, and 52, the ABS 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 cleared, the CPU resets, and the indicator goes off right after the engine is started if the system is OK.
- The ABS is not operational when the ABS indicator is ON; the VSA is not operational when the VSA system indicator is ON.
- When the VSA system indicator and MIL are both ON, troubleshoot/he PGM-FI system first.

Diagnostic Trouble Code (DTC)
- All of the VSA DTCs are indicated by the ABS indicator blinking.
- The memory can hold any number of DTCs. However, when the same DTC is detected more than once, the more recent DTC is written over the earlier one. Therefore, when the same problem is detected repeatedly, it is memorized as a single DTC.
- The DTCs are indicated in ascending number order, not in the order that they occur.
- The DTCs are memorized in the EEPROM (nonvolatile memory). Therefore, the memorized DTCs cannot be canceled by disconnecting the battery. Perform the specified procedures to clear the DTCs.

Self-diagnosis
Self-diagnosis can be classified into two categories:
- Initial diagnosis: Done right after the engine starts and until the ABS or VSA system indicator goes off.
- Regular diagnosis: Done right after the initial diagnosis until the ignition switch is turned OFF.
- When a problem is detected by self-diagnosis, the VSA control unit shifts to fail-safe mode.

Kickback
The pump motor operates when the ABS is functioning, and the fluid in the reservoir is forced out to the master cylinder, causing kickback at the brake pedal.

Pump Motor
- The pump motor operates when the ABS or VSA is functioning.
- The VSA control unit checks the pump motor operation during initial diagnosis when the vehicle starts moving. You may hear the motor operate at this time, but it is normal.
- The pump runs at 7 mph and again at 15 mph.

Brake Fluid Replacement/Air Bleeding
Brake fluid replacement and air bleeding procedures are identical to the procedures used on vehicles not equipped with ABS/VSA. To ease bleeding, start with the front wheels. Replace the VSA fluid in the modulator reservoir after replacing the brake fluid.