External inspection
Before diagnosing an ABS malfunction, fully determine whether the normal brake system is in working order or not. Many common brake problems (loose parking brake, leaking, etc.) will affect the operation of the ABS. Visual inspection of specific system components can identify the causes of external ABS malfunctions and identify simple failures, thus reducing diagnosis time.
1. Check your tire pressure; they must be approximately the same for the system to function properly.
2. Check the brake fluid level in the reservoirs.
3. Check lines, hoses, master cylinder assembly and brake calipers for leaks.
4. Visually inspect brake lines and hoses for excessive wear, thermal degradation, punctures, contact with other parts, missing fasteners, snagging or deformation.
5. Check the calipers for rust or corrosion. Check for proper sliding if necessary.
6. Check the calipers for freedom of movement when applying and releasing the brakes.
7. Inspect the wheel speed sensors for proper installation and fastening.
8. Inspect the speed sensor gears for broken teeth or loose fittings.
9. Inspect the wheels and tires on the vehicle. They must be the same size and type to generate accurate speed signals.
10. Recheck the location of the fault. Certain situations caused by the driver's actions, such as not fully releasing the parking brake, spinning the wheel during acceleration, slipping due to excessive speed on a turn, or driving on extremely rough roads, will set a fault code and turn on the hazard warning lights. These "malfunctions" are not system failures, but are examples of operating the vehicle under conditions that interfere with the operation of the control unit.
11. Often the system will shut down due to a loss of sensor signals to or from the control unit. The most common cause is not a faulty sensor, but a loose, corroded or dirty connector. Check the harness and connector components carefully.
Checking the warning lamp
Once the warning light comes on, it stays on until you turn the ignition off and then back on, or the code (if any) is reset. The easiest way to check the system is to simply turn the ignition on and check for the warning light. Start the engine; if the signal goes out after a few seconds, the system is working without errors. If the lamp does not go out, then further diagnostics in the workshop is required.
If the warning lamp does not light when the ignition is turned on, check the bulb, the open circuit from fuse 13 on the Prelude or 1 on the Accord to the instrument cluster, the open circuit of the blue-red wire from the instrument cluster to the ABS control unit. There may also be no reliable connection between the control unit and the housing (open circuit of the "ground" circuit).
The light may remain on after the engine has been started. Common causes are a broken or poor connection between the ABS harness and the control unit, a defective ABS fuse (2 on Accord or 27 on Prelude), or an open circuit in the white wire between the ABS fuses (2 or 27) and the control unit. The fault may also be caused by an open circuit between fuses 17 (Prelude) or 8 (Accord) and the safety relays, or an open/short circuit in the yellow/green wire to the safety relays. Additionally, check for an open circuit in the white/blue wire between the alternator and the control unit. Also check for an open/short circuit in the blue/red wire from the measuring unit to the control unit.
The warning lamp lights up if the battery voltage drops below the normal level. Once the voltage is restored, the system functions normally.
The electronic control unit of the ABS system has self-diagnostic capabilities, similar to the fuel injection system. If the electrical signal goes beyond the operating range, the control unit determines this condition and turns on the ABS warning lamp. The error code is stored in the system memory for subsequent identification.
Diagnosing the system requires the use of a Honda ABS tester. This is a sophisticated test tool available only at dealerships. In the event that the vehicle's warning light remains on during normal operation, carefully check simple things. The most common causes of error or signal loss are not the most difficult to detect.
If the problem is not resolved by your efforts, have your vehicle inspected by your HONDA dealer.
(Based on materials from the website «HONDABOOK.ru»)