BMW 1150 ABS Diagnosis

BMW 1100/1150 ABS system checks

iABS fault codes for my 2004 BMW GS Adventure.

Similar codes should be listed on the sticker supplied with your bike.

Gen OFF, ABS ON = Only residual braking in both circuits.
Gen OFF, ABS flashes at 1Hz = ABS not available. Pull-away test not completed.
Gen OFF, ABS flashes at 4Hz = Only residual braking function available in both circuits.
Gen ON, ABS off = rear light/brake light defective.
Gen ON, ABS flashes at 1 Hz = At least one brake circuit without ABS.
Gen ON, ABS flashes at 4Hz =At least one brake circuit in residual braking function mode.
Gen AND ABS flashing alternately at 1Hz = Fluid level in Integral ABS too low.Low-voltage

Try and ABS reset according to the procedure in your owner's manual.

Full and fresh brake fluid is a given, do not skimp here. Do the maintenance or have it done at least as often as recommended by BMW.

Front and rear micro switch test. They should click loud enough to hear them engage but this by no means is an indication of proper operation. Check for proper switch operation with a DMM.

Get a DMM "digital multi-meter" and learn how to use it.

For IAbs sytems, both front and rear switches as NC (normally closed) the opposite of typical motorcycle brake light switches. Therefore is they are engaged at start up, an ABS error occurs because of an open circuit in the system.

Earlier ABS1 and ABS2 have normally open switches for the brake light actuation.

Make sure the hand guard is not touching the front brake lever.

Make sure the metal tab on the rear brake switch is making proper contact with the rear pedal assembly.

Check your front and rear brake switched again as MOST PROBLEMS ARE SWITCH RELATED!

Test rear brake light bulb. If you are having problems and have an aftermarket brake light installed, put the stock bulb back in a test. Test the tail light element and the brake light element of the bulb.

Check ABS sensor gaps and the "spoke rings" they use to sense wheel speed.

Dirty sensors, sensor gap too large, debris, dirt, missing or damaged "ring" spokes can all add up to an ABS fault condition. ABS sensor gap 0.45...0.55 mm (0.018 ... 0.022 in) (front and rear).

Battery condition, the bike starts fine, what's the problem?

If the battery voltage drops too much while starting it starts throwing ABS error codes from the get go.

Brake pad condition? Although this has been argued back and forth, if the pads on either end of the bike are near the end of their service life, replace them. At least one person has claimed this fixed his ABS problem. More likely the movement of brake fluid through the system after the pad change fixed the problem but I digress.

Try taking off both battery cables and touching them to each other.

If all else fails, disconnect the battery and let sit for 30 minutes, reconnect battery and give it a try.