tiafn2

So I have the usual TCS OFF and ABS INOP lights on my dash. I've read thru some of the past posts on this topic and I see a lot of suggestions to check the wheel sensors. That seems like a simple thing to start with except for the fact that I'm not sure where they are. I replaced a front hub a couple years ago and remember there being a connection on there...is that the sensor?

Additionally my emergency brake light is on as well...would this point to it being one of the rear wheel sensors?

Chevyssoccer

yes to the first one, I dont think so to the second.

tiafn2

Ok well I at least know where they are now. Much appreciated. Any advice/suggestions on how to check and how to clean if needed?

Injuneer

You don't mention the year of your car, but since TCS was not available until 1995, we'll ASSume that you have a 95 or newer. Since you have TCS + ABS, your car has 4 wheel speed sensors. The two front sensors are in the hub cartridges, the two rear sensors are on the axle endplates.

If you only had ABS (no TCS), there would only be one sensor for the rear, and that would be on the top of the differential housing.

The "BRAKE" light serves two functions: 1) E-brake is on, or switch is stuck; 2) the pressure differential switch on the side of the ABS unit has detected a difference between the hydraulic pressures in the front and rear braking systems. Logically, if the system detects uneven pressure in the front and rear systems, it may disable the TCS and ABS systems. The "BRAKE" light may be the cause of the "TCS OFF" and "ABS INOP" lights.

You could verify this by having the EBTCM scanned for codes. Unfortunately, this can only be done with a high end tool like the GM shop's Tech-2, or other high end scanners. In lieu of scanning for codes, check the fluid level in the master cylinder, and look for leaks in the brake lines or at the calipers.

tiafn2

Appreciate the info. I will check the brake system and if nothing else take it in to the dealership to get the codes scanned. FYI, it's a 2002 Firehawk with TCS.

Just a thought but would bleeding the system possibly fix the pressure differential?

Injuneer

If the problem is caused by air in one of the lines, then bleeding would solve the problem. That is one of the causes of unequal pressure, as a result of the master cylinder being low, or a leak in the system. But you still have to determine why it got air in the system.