ABS Pump Motor Problems

Even though it would seem an article devoted to ABS (anti lock brake system) pump motor problems would only interest a few people this isn’t the case. Common problems with certain systems affect thousands of people that drive these automobiles. As an example we’ll cover problems with the Kelsey Hayes brake system installed on General Motors trucks and vans from 1999 through 2005.

These automobiles often experience a situation where the pump motor continuously runs even with the key off. We’ll also touch on mid-90s Honda’s and Acura cars that set an ABS code for pump motor run on. Although we focus on common failures here, automotive enthusiasts should enjoy learning about the common problems that fly under the radar yet cost motorists thousands of dollars every year. Enough people are affected that profitable businesses developed around solving electronic brake control module problems for car owners.

ABS Pump Motor Operation

There are many different kinds of ABS out on the roads today. The new systems make the old ones look like an experimental project gone wrong. Here we’re focusing on the operation of mid-1990s through mid-2000 vehicles. This target decade saw a lot of changes and improvements to standard ABS equipment. These systems have a brake fluid pump motor used in combination with an accumulator.

The electric pump motor is used to provide pressurized hydraulic fluid for the braking system. The pump is controlled by a module that tells it when to turn on and turn off. The accumulator works together with the motor as it’s used to store hydraulic fluid to maintain a high level of pressure in the brake system and provide residual pressure for power assisted braking if a problem develops.

During normal operation the pump motor kicks on until the pressure reaches over 2500 PSI (pounds per square inch) and then it shuts off. After pressure falls below 2000 PSI the motor is activated again and will continue this cycle of normal operation. There are a few other components involved such as a pressure switch and a relay. The control module uses the pressure switch as an input and operates the relay as an output control.

Pump Motor Run on

The condition is described as ABS run on. The definition is the brake pump motor continues to run at all times regardless of the key position being on or off. People often describe this as walking away from the vehicle but they still hear something running. This is a common complaint from drivers of automobiles that have deployed the Kelsey Hayes ABS.

For identification purposes if you locate the control module assembly it will say Kelsey Hayes right on the top module cover. You’ll find this system on light trucks from the model year 1999 through 2005. This includes popular models like the Chevrolet Astro van, Tahoe, Silverado, as well as their GMC counterparts like Yukon, Safari vans, and Sierra pickups.

Solving ABS Motor Run On

The failure has been isolated to a transistor on the circuit board that controls the output or relay operation. When this transistor fails it turns on the relay and no longer has the ability to turn it off. The problem for vehicle owners is continuous operation of the pump will drain the battery if they walk away and let it run. There are two ways to turn it off until the problem is resolved. You can locate the fuse and remove it from the panel. You can also locate the two wire power connector at the motor itself and disconnect it.

When motorists seek permanent solutions for the problem there are several ways to handle the repairs. Each auto repair center might prefer to follow a different procedure but ultimately the owner decides. Dealerships tend to want to replace the module with a brand-new part. This can often be the most expensive way to go. The defective module can also be replaced with a re-manufactured unit. The final solution is probably the least expensive and that would be to send out the originally installed control module to a repair center such as module master’s. This business was created to solve common problems with different types of electrical components.

Overrun Codes on Honda and Acura Vehicles

Another common complaint on Honda and Acura automobiles from the mid-90s is an ABS pump overrun code. On this type of system the motor is activated when the key is on or the engine is started. The pump is run until proper pressure is achieved and then turns off. If it runs for more than 40 seconds the control module will consider this a problem and set a code to let the driver know an issue has developed.

The overrun situation needs to be diagnosed on an individual basis as several different failures have been found with these types of vehicles. Sometimes the overrun code is set properly and points to a pressure building malfunction. Some common issues reported would be brake fluid leaks that prevent the system from reaching the turn off pressure. Also reports of an O ring failure at the accumulator have been identified to cause this trouble code. On top of these items failed relays where the contacts become stuck closed can cause the pump to run.

This article about common ABS pump motor problems addresses vehicles from the mid-90s and stretches to ones built up until about 2005. These autos have long since been out of warranty leaving the owner to pay for all repairs out of pocket. Some might consider these cars and trucks old and not worth fixing but too many medium to low income families these vehicles are considered in the prime of their lives.

When failures become so common they affect millions of drivers businesses will find solutions to repair them more efficiently. In the end this allows them to offer lower total prices while maintaining profit margins. If these common problems are affecting you, discuss the options with the auto repair center instead of just saying yes to the first estimate. Educated car owners can get these ABS systems repaired for a reasonable amount of money.