Yamaha MTN850-A 2017, Service Manual, Page: 480 / 560

ABS (ANTI-LOCK BRAKE SYSTEM)
8-123
EAS30845
MAINTENANCE OF THE ABS ECU
Checking the ABS ECU
1. Check:
• Terminals “1” of the ABS ECU
Cracks/damages

Replace the hydraulic unit assembly, brake hoses, and brake pipes that are
connected to the assembly as a set.
•
Terminals “2” of the ABS ECU coupler
Connection defective, contaminated, come-off

Correct or clean.
TIP
If the ABS ECU coupler is clogged with mud or dirt, clean with compressed air.
EAS30528
ABS TROUBLESHOOTING OUTLINE
This section describes the troubleshooting for the ABS in detail. Read this service manual carefully and
make sure you fully understand the information provided before repairing any malfunctions or perform-
ing service.
The ABS ECU (electronic control unit) has a self-diagnosis function. When failures occur in the system,
the ABS warning light on the meter assembly indicates a malfunction.
The following troubleshooting describes the problem identification and service method using the
Yamaha diagnostic tool. For information about using the Yamaha diagnostic tool, refer to “[B-2] DIAG-
NOSIS USING THE FAULT CODES” on page 8-127. For troubleshooting items other than the following
items, follow the normal service method.
WARNING
EWA16710
When maintenance or checks have been performed on components related to the ABS, be sure
to perform a final check before delivering the vehicle to the customer.
TIP
To final check, refer to “[C-1] FINAL CHECK” on page 8-147.
ABS operation when the ABS warning light comes on
1. The ABS warning light remains on

ABS operates as a normal brake system.
•
A malfunction was detected using the ABS self-diagnosis function.
• The ABS self-diagnosis has not been completed.
The ABS self-diagnosis starts when the main switch is turned to “ON” and finishes when the vehicle
has traveled at a speed of approximately 10 km/h (6 mi/h).
2. The ABS warning light comes on after the engine starts, and then goes off when the vehicle starts
moving (traveling at a speed of approximately 10 km/h (6 mi/h)).

ABS operation is normal.
3. The ABS warning light flashes

ABS operation is normal.
• Refer to “BASIC INSTRUCTIONS FOR TROUBLESHOOTING” on page 8-124.
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