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7.8 - Brake Pad Sensing ( )

There is a wealth of data in the archives about this!!!!

The brake pad sensing is just a single wire circuit through the sensors in the inner pads on all four wheels (two wheels on the 1990 and later cars, up to some point when they were eliminated entirely).

When the circuit is grounded, you get the low pad warning. This is typically when the pad is just worn to the point that the sensor wire in one of the pads contacts the brake rotor when the brakes are applied. The warning goes out when the brakes are released and the ground contact is broken when the pad retracts.

When the circuit is broken, you get the low pad warning all the time. This happens when the sensor wire finally wears through. It can also happen if there is a break in the wiring to the sensors.

To identify the source of the problem, you just need to get an ohmmeter and trace the wiring. The loop runs from pins LB54-2 of the instrument pack connector, through all of the pads, and back to pin LB54-3 of the instrument pack connector.

It looks like:

LB54-2 Brake pad feed OUT
LB54-3 Brake pad fail sensor IN

LB54-2 ---------Right front--------Right rear---------|
LB54-3 ---------Left front---------Left rear----------|

I would start by disconnecting the instrument pack connector and measuring between either LB54-2 or LB 54-3 and ground. If you have continuity, there is a short to ground in the circuit and the problem is not a pad sensor. If there is no continuity to ground, next check for continuity between LB54-2 and LB54-3. If there is no continuity then you have a break in the circuit. With your symptom (warning on all the time) you have either a short to ground or a break in the circuit which should be there all of the time. You will need to work your way around the circuit, checking each leg of the circuit until you find the problem.


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