ABS (Anti-lock Braking System)
Diagnostic switch location
The most common location for the ABS diagnostic switch is under the dashboard cowl.
Here you will typically find two (2) Momentary Switches
- Left = Engine
- Right = ABS Diagnostics.
Blink Codes
The ABS performs a diagnostic check each time the ignition is switched on. If the ABS indicator light remains on, or illuminates while the motorhome is being moved, there may a fault within the anti-lock brake system. You can retrieve the fault code using the diagnostic switch and recording the blink codes. Turn ignition key to the ON position, wait three seconds then press and hold the momentary abs switch for one to two seconds then release it. The dashboard abs light will now “blink” the code, first digit, short pause, second digit.
| Blink Code Identification | |
|---|---|
| First Digit (Type of Fault) | Second Digit — Specific Location of Fault |
| 1 No faults | 1 No Faults |
| 2 ABS modulator valve 3 Too much sensor gap 4 Sensor short or open 5 Sensor signal erratic 6 Tooth wheel | 1 Right front steer axle (curb side) 2 Left front steer axle (driver’s side) 3 Right rear drive axle (curb side) 4 Left rear drive axle (driver’s side) 5 Right rear/additional axle (curb side) 1) 6 Left rear/additional axle (driver’s side) 2) |
| 7 System function 3) | 1 J1922 or J1939 datalink 2 ATC valve 3 Retarder relay (third brake) 4 ABS indicator lamp 5 ATC configuration 6 Reserved for future use |
| 8 ECU | 1 Low power supply 2 High power supply 3 Internal fault 4 System configuration error 5 Ground |
Resetting the ABS Light
- Turn Ignition Key On
- Press ABS switch Momentarily
You can try re-seating all the connections on the ABS Wabco box, the light has been known to trigger due to a momentary connection issue. The WABCO box is silver and usually in the bay with the HWH pump and inverter. Unplug each connector from the box and then plug it back in (one at a time). If you have corrosion X available use it on the connection before you re-seat them. You will need to drive a short distance to have the light reset if this was the problem.
ABS Light Function
- ECU Rev C : The ABS warning lamp comes on when the ignition switch is activated. The lamp goes out when the speed of the vehicle reaches approximately 4 mph (6 km/h). If the warning lamp remains lit or comes on at any other time during vehicle operation, it signals a malfunction in the ABS
- ECU Rev D (started around 2000-2001): ABS lamp comes on at ignition momentarily for a bulb check, then goes out. If there is an Existing Fault the ABS lamp does not go out at ignition. If Lamp does not go out at speeds above 4 mph (6 km/h) — a fault still exists in the ABS system.
- ECU Rev E (somewhere around 2010?) Same start-up as Rev D
