"Brake" and "ABS" lights intermittent

[Clayboy]

I have a 92 D350 and the brake and ABS lights are intermittent. I detect no issues with the brakes, in fact the previous owner stated it recently had all brakes replaced and the shop told him he has a bad "sensor. " I don't doubt the brakes were worked on - at least I can tell the fronts have new/newer calipers and plenty of pad. The only sensor I can think of which may give me these indications is the AS sensor. As stated, they do not always come on, they come on and go off. Could a short also give me these indications? I have not chased the wires to see if I am making any kind of contact. Is there a way to trouble shoot before I haul off and start replacing things? Thank you for any insight.

Clayboy

 

[JLEONARD]

Many of us simply disconnected the plug from the module behind the glove box. No more light, and the brakes always worked fine.

 

[RWherley]

My ABS light has been on for as long as I have had my truck, this fall by bypassed the ABS valve and I think the brakes are better now.

 

[DMcLeod]

Check the low vacuum warning switch.

The switch is in circuit with the brake warning light, and is located on the drivers side inner fender just below the hood hinge. A vacuum line connects the switch to the brake booster. If booster vacuum falls below 8. 5 inches for 8-10 seconds or more, the sensor illuminates the brake warning light. You can use a hand held vacuum pump to test the switch operation, and use a vacuum gage to check your vacuum system for leaks.



This is just one piece of the puzzle that I recently went through on my 92.

 

[RSchwarzli]

Willing to bet if you pull the harness off the diff sensor and shine a flashlight down the harness connector, you will find green rot. About to install harness #3 on my truck in 11 years. VERY common issue for these old trucks.

 

[Clayboy]

The switch is in circuit with the brake warning light, and is located on the drivers side inner fender just below the hood hinge. A vacuum line connects the switch to the brake booster. If booster vacuum falls below 8. 5 inches for 8-10 seconds or more, the sensor illuminates the brake warning light. You can use a hand held vacuum pump to test the switch operation, and use a vacuum gage to check your vacuum system for leaks.



This is just one piece of the puzzle that I recently went through on my 92.

Thank you. very helpful and I will check.