Description of On-Board Diagnostics

General Troubleshooting Information
ABS/TCS Indicators
- If the system is OK, the ABS indicator goes off once after turning the ignition switch ON (II) without starting the engine, and then comes on again and goes off several seconds later after starting the engine. This occurs because the ABS/TCS control unit is turned on by the IG2 power source.
- The TCS or ABS indicator comes on when the TCS control unit detects a problem in the system.
However, even though the system is operating properly, the TCS or ABS indicator will come on, under the following conditions:
- For ABS or TCS Indicator:
- Only drive wheels rotate
- One drive wheel is stuck
- The vehicle goes into a spin.
- The ABS continues to operate for a long time.
- The vehicle is subjected to an electrical signal disturbance.
- For TCS indicator:
- The TCS operated when the front brake pad temperature was excessively high.
- The TCS switch is OFF.
- One or more of these components are faulty: 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 sensor, Idle air control valve, VTEC pressure switch, Knock sensor, Fuel supply system, Automatic transaxle, Misfire detection system of the PGM-FI system.
To determine the actual cause of problem, question the customer about the problem, taking these conditions into consideration:
- When a problem is detected and the ABS or TCS 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 ABS 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 ABS DTCs 12, 14, 16, 18, 21, 22, 23, 24, 51, 52 and 53, 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 TCS is not operational when the TCS indicator is ON.
- When the ABS and TCS indicators are both ON, troubleshoot the ABS first.
- When the TCS indicator and MIL are both ON, troubleshoot the PGM-FI system first.

Diagnostic Trouble Code (DTC)
- 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 2 categories:
- Initial diagnosis: Performed right after the engine starts and until the ABS or TCS 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 ABS/TCS 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 is functioning.
- The ABS/TCS control unit checks the pump motor operation during initial diagnosis when the vehicle is started. You may hear the motor operate at this time, but it is normal.

Brake Fluid Replacement/Air Bleeding
Brake fluid replacement and air bleeding procedures are identical to the procedures used on vehicles not equipped with ABS/TCS. To ease bleeding, start with the front wheels.