Introduction
If your Anti-lock Brake System (ABS) warning light is on, it is probably due to an issue with one of the ABS sensors. Unfortunately, diagnosing which sensor is faulty isn’t always a straightforward task, especially if you don’t have access to a diagnostic scanner. This article aims to provide you with several methods to identify which ABS sensor is bad even without a scanner.
Visual Inspection
One of the first things you can do is conduct a visual inspection of your ABS system. This can sometimes give you clues as to which sensor is giving trouble.
Begin by inspecting the wires and connectors that run from your ABS sensors to the brake system. Look for any cracks, breaks, or signs of wear. If you see any obvious damage, that can give you an indication of which ABS sensor is likely the culprit. You can then visually isolate the sensor from the rest of the wiring and connectors.
Another thing to look for is physical damage to the ABS sensor itself. The ABS sensors are located behind the brake rotor. Look for any physical damage to the teeth on the wheel bearings, as this is a sign that the sensor needs to be replaced.
Resistance Testing
Resistance testing helps you assess whether the sensors have broken wires or if the electronic component is faulty. Here’s how to proceed:
1. First, remove the sensor from the vehicle axle, usually it should be held by one or two bolts.
2. Set your digital multimeter to measure resistance.
3. Touch one probe on one of the two sensor pins and touch the other probe on the other pin.
4. The multimeter display should read some resistance value, if you read an over limit or infinite measure, it means the circuit inside the sensor is open or cut which implies that the sensor is faulty.
5. Repeat the process for the second sensor.
Spin Test
The spin test is designed to identify if a sensor is producing a signal. Here’s how you perform the procedure:
1. Remove the wheel and tire assembly to gain access to the sensor.
2. Position your digital multimeter to AC voltage.
3. Turn your ignition on and rotate the wheel by hand to speed up the sensor signal.
4. Connect the probes of the multimeter to the connectors of the sensor.
5. If the multimeter shows a varying voltage signal with respect to wheel speed, the sensor is fine. If not, it means the sensor is no longer operational.
Thermography
Thermography means using an infrared camera that visualizes the heat signature of an object. Here’s how the process works:
1. Start your vehicle and allow it to warm up to operating temperature.
2. Next, take a thermal image via the infrared camera of each of the ABS sensors, including the wiring and connectors.
3. A hotter-than-normal sensor or a substantial difference in temperature between one sensor and all the others means that sensor is faulty.
One of the main advantages of thermography is that you don’t have to touch or remove any parts to perform the test. A disadvantage of using thermography, though, is that it requires expensive equipment.
Diagnostic Trouble Code
An On-Board Diagnostics (OBD) system uses codes to indicate faults in the vehicle. A scanner is required to retrieve these codes. Here’s how to proceed:
1. Plug the OBD scanner into the vehicle’s diagnostic port.
2. Turn on the ignition and follow the scanner’s instructions to retrieve the codes.
3. Look for the codes related to ABS sensors and interpret as per the scanner’s instructions.
4. The code will typically contain a description that will tell you if the issue on a particular sensor is intermittent or ongoing.
Open Circuit Test
An open-circuit test can diagnose broken or cut wires in an ABS sensor. These are the steps to follow:
1. Dependably raise your vehicle with a jack and hold it up with jack stands before starting any work.
2. Remove the wheel and tire assembly to access the sensor.
3. Consult the service manual for the correct wiring schematics for your car’s specific ABS sensor.
4. Turn the ignition switch on and activate the brakes pedal.
5. Next, use the ohmmeter to touch the sensor’s pins, and check for continuity between each of its pins.
6. A reading indicates that the wires are fine, while if there’s an over-limit measure, it means that one or both of your sensor cables are cut, and the sensor is faulty.
Conclusion
Although diagnosing which ABS sensor is bad without using a scanner can be somewhat challenging, the above-discussed methods can be useful. Performing multiple tests can definitely increase the accuracy of the diagnosis.
It is also worth noting that in some instances, it may be most effective to replace all of the sensors at the same time, especially if they are of the same age. This procedure, however, could be expensive. By using the methods, you should be able to troubleshoot your vehicle’s ABS sensor issues effectively. Use visual inspection, resistance testing, spin test, thermography, diagnostic trouble codes, or open circuit tests to get an accurate diagnosis.