Hmmm, sounds like you covered pretty well. Is that dash lamp the same as the parking brake? Is parking brake engaged?

 

Hello Bork,
Thanks for responding. I thought I checked the parking brake, but I think I forgot to write it down. I know I checked the function of the parking brake switch with a multimeter. Just to be sure, today I'll:

• Disconnect the master cylinder sender and check the operation of the parking brake for the proper lamp signal. (I expect a DTC code might be stored after doing this.) I do remember proper operation when I did this before, but I'll check again.
• Disconnect both connections from the master cylinder sensor and parking brake switch. I expect no light. Perhaps this will eliminate any other shorts in the circuit that might cause the brake warning light?
• Remove each wheel and inspect pad lining thickness.

IIRC, the brake warning light is a dual-function lamp (or maybe there's another lamp that looks like this (o) ?. The first function as an indicator of a brake system fault and the second as an indicator that the parking brake is engaged.

I'll report my results after I'm done.
Cheers from Seattle,
Eric

 

Ok, results after round two:

• Disconnected the master cylinder sender. Results: brake warning light is on. Noted flicker when operating the parking brake. No DTS codes noted. Shouldn't one of these leads be grounded when I run this test?
• Disconnected both master cylinder sender and parking brake switch. Results: brake warning light is on. No DTS codes noted. Again, should one of the leads be grounded while testing?
• Inspected all brake pad linings. The minimum lining thickness per manual is 0.060 inches. All pad thicknesses are greater than the mechanical wear limiter. Recorded the following pad thicknesses:

Inside / outside​

• left front 0.161 / 0.233
• right front 0.223 / 0.208
• left rear 0.262 / 0.245
• right rear 0.255 / 0.224

The front pad sets are getting close to replacement. At this point, I do not think that they're the cause of my brake warning light. Am still puzzled.

 

The brake pad linings will not directly cause a brake warning light. But as the linings wear, the brake fluid level drops. I usually top off brake fluid only after changing pads. If you top off the fluid and later change your pads, you could overflow the master cylinder when the new pads are installed! (Now how would I know that !) And it's a good practice to flush the fluid after changing the pads.

 

Hello kernel,
You're quite right. I've also caused an overflow on my pickup when I pushed the pistons back into the caliper. One of the things I did here was to check and fill the reservoir early on. Much to my disappointment, the brake warning light remained on. My effort continues.
Cheers,
Eric

 

The latest: I used the old master cylinder cap sender to determine circuit status. When the float is down the circuit is closed (a low fluid condition - continuity on the multimeter - Brake Warning Light (BWL) on the cluster.) When the float is up we have no continuity in the circuit, and thus no Brake Warning Light. Here, I've again disconnected the leads and taped-off the ends to avoid any shorts to chassis.

When the parking brake is down (disengaged) the switch plunger is pushed down opening the circuit, and no light (even the separate lamp like this (o) one) should show on the instrument cluster. When the parking brake is engaged, the spring pushes the contacts closed (continuity in the circuit.) and we'll have a light on the cluster.

Behold, that irritating BWL is still lit. This suggests to me that there's something else causing this condition. Regrettably, throughout all of this, I neglected to previously mention that the battery light is also lit, and has been present since the start of this problem. I think I should pull the alternator and have it checked. I think the battery itself is good because I put it on an overnight charge and the brake light was still present the next day. (Plus the electrolyte levels were good too.)

If anyone has any ideas, please don't hesitate to say so.
Befuddled in Seattle,
Eric

 

The battery light is meant to indicate to the driver that the alternator is not charging the battery. On many vehicles the brake light will illuminate with the battery light. This is a normal condition. I'd concentrate on the battery light issue first.

 

Howdy John,
Thanks for that info. My next step is to pull the alternator and have it and the regulator checked at the shop.
Cheers,
Eric

 

As a side note, when you get to your front brakes, take a look at that left side caliper and slide pins. The difference in pad thickness between the inner and outer pad suggests something in the caliper is binding a bit. It could be sticking slide pins or it could be pads sticking in the bracket. It has nothing to do with your brake warning light but just thought I'd pass along to look at when you're doing your front brake job.

 

Good tip and no worries. I wouldn't be surprised if the pins are sticking a bit. I usually do all pads forward and/or all pads rear so I'll take a look.

 

Hello John,
The alternator failed the test at the parts shop. Now waiting for the replacement to arrive from the warehouse. I'm going to make a note in my Clymer manual in the troubleshooting section concerning an alternator fault as related to a master cylinder fault light.
Cheers,
Eric

 

Also write down in your Chilton manual to ONLY use a Denso reman alternator. Anything else will likely cause issues down the road if not right out of the box.