The yellow brake warning light indicates open loop in the brake pad sensors
It is a wire, coming from the controller through the left wheel pad, through
the right wheel pad and to chassis. The loop should be normally closed. When
a pad is worn, it sensor opens the circuit.
I can recoomend the following narrowing down procedure:
1. Turn the steering wheel left and inhook the harness connector from the
wheel sensor. Check with Ohmmeter the pad. It should be short circuit. If
found open, you can insert a jumper wire in the harness connector (to short
it) and plug it back.
2. If the pad is OK, turn the steering to the right and repeat the process
on the right wheel.
3. If both pads are OK, yet the light is still on - the problem is in the
4. Go back to the left wheel, unplug the harness connector and jumper
temprarily both its pins to chassis. If the light is still lit the wire from
the controller to the left wheel is broken.
5. If the light is not lit - repeat the test on right wheel.
Bear in mind that the wires flex and get fatigued. It is common for them to
fail at certain time.
It is common for garages to bypass them too. I had to replace the wire on my
previous 1987 5000S and 51986 000TQ
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