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Hal, Chevy Master Tech
Category: Chevy
Satisfied Customers: 1031
Experience:  ASE and Chevy Master , 31yr Dealership exp,
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2002 Impala: the ABS not working..front brakes..rear brakes

Customer Question

Is it unsafe to drive a 2002 Impala with the ABS not working? The car has 115000 miles. The front brakes were replaced the rear have not been replaced and I do not know the condition of the rear brakes. Is it possible the wheel sensors will give codes that would indicate the EBCM and BPVM are bad when they are not? The dealer wants to change both for $3300.
Submitted: 6 years ago.
Category: Chevy
Expert:  Hal replied 6 years ago.

Hi my name is XXXXX XXXXX Your complete satisfaction is my goal. Please provide as much information about your concern as you can


The brake system will operate as a vehicle that does not have antilock brakes. It is safe to drive as long as you are aware of this and allow for it when you are stopping. This may cause some longer stopping distances depending on road conditions.


Wheel speed sensor codes usually do not require a BPMV to be replaced. The BPMV is the brake pressure modulator valve. It has nothing to do with wheel speed sensors.


The EBCM is the electronic brake control module. It reads the wheel speed sensor input to adjust the BPMV solenoids to control the brakes if they lock up.


Usually the wheel speed sensor issues are due to the sensors them selfs, or the wiring from the sensor to the EBCM.


With out the diagnostic codes that were set and knowing what kind of testing was performed and the results of those test. I can not say why they would want to replace both components, unless they are making an educated guess, because the concern is not present while they are testing it.


If you have new information to this concern please let me know. You can ask follow up questions if needed.

Thank You


Customer: replied 6 years ago.
I expect that the only thing that was done is the fault codes read. I will try to find out what the codes are and if anything else was done. Are the codes that are set when rear wheel sensors go bad/or brakes are down to backing plates different than the codes for faulty control modules?
Expert:  Hal replied 6 years ago.
All the wheels will set codes specifically for the sensor signals and circuits. The EBCM will set codes for internal concerns separate from wheel speed sensor codes. This is why it is important to know what codes have set. Just because a codes has set does not automatically mean the component is bad. It just means the EBCM has recognized the circuit is not performing with in parameters. The wiring and connections all have to be inspected to make sure it is not just a poor connection causing the trouble code to set, or a wire that is grounding out.
Customer: replied 6 years ago.
One last question. The original problem was probably mistated a little. The problem that made my son take the car in was the ABS light and the Traction Control light coming on. The garage apparently read the codes and said the EBCM and BPMV needed to be replaced. We still do not know what the codes were that set. I don't know if they will give us that yet or not. He is taking the car to another garage to have someone else look at it. The more appropriate is what things will turn on the ABS and Traction Control Light other than the two control modules? I assume the circuit problems that you mentioned would do it are there other things that would?

Expert:  Hal replied 6 years ago.

No problem. Items that can turn the ABS /traction control lamps on other than the modules are. #1 any wheel speed sensor or circuit wiring. Data communication circuits, brake fluid level, power and ground to the EBCM.


Here are the trouble codes that can set for ABS concerns.

  • DTC B2747
  • DTC C1214
  • DTC C1216
  • DTC C1217
  • DTC C1218
  • DTC C1221-C1235
  • DTC C1236
  • DTC C1237
  • DTC C1238
  • DTC C1242 or C1243
  • DTC C1248
  • DTC C1254
  • DTC C1255 or C1256
  • DTC C1261-C1274
  • DTC C1276, P1644, or P1689
  • DTC C1277 or P1571
  • DTC C1278
  • DTC C1291
  • DTC C1294
  • DTC C1295
  • DTC C1298


    All of these codes deal with a circuit in the ABS system. SO knowing which code is set is critical for diagnosis.


    If a repair shop will not give you the code,and WHY the component needs replaced. Find another repair shop! This is what you are paying the diagnostics fee for. Example: This is the code that set C000 . it has set due to a faulty connection at the wheel speed sensor. Replacing the wheel speed sensor is the only way to get the connector. ( Or) the EBCM has set a code C000 for an internal fault. replaceing the EBCM is the only way to repair this code because there is no way for us to repaire the internal circuit.



    If they diagnose the concern, and find the root cause for the concern, you as the paying customer have the right to ask WHY this component needs replaced. If they can't tell you with confidence, or are unsure why, they are guessing. These components are Expensive, do not throw parts at this problem on a hunch. Propper diagnostics can find the cause , and if they can not find the cause, who ever performs your diagnostics should at least be up front and tell you that this is an educated guess based on XYZ. So the ultimate decision is yours with the properer information as to what is going on with your vehicle.


    After you get the trouble codes, feel free to let me know and I will look them up and give you the possibilities that could be the cause.


    Thank you


    Hal and 5 other Chevy Specialists are ready to help you
    Customer: replied 6 years ago.
    Smile I felt your service was very professional and was at the level of detail that I was looking for. Although the links on the codes did not work if they were suppose to. Is this where feedback is to be left?
    Expert:  Hal replied 6 years ago.

    The links to the codes will not work for you through this sight. If you can get me the codes number I will get you the description and diagnostics associated with the code.


    I just included the code numbers to show you how many different codes were on this system that can cause a concern.


    Again feel free to run the diagnostic you receive from the repair shop by me if you need to to be able to make an informed decision.