Diagnostic Trouble Code
P215A
Vehicle Speed - Wheel Speed Correlation
Technical Description P215A
Vehicle Speed - Wheel Speed Correlation
Severity Level P215A
The conditions which contribute to a code P215A being stored may result in ABS deactivation or erratic transmission shifting patterns. The code should be considered severe and addressed as quickly as possible.
What Does This Mean P215A?
This is a generic diagnostic trouble code (DTC) and typically applies to OBD-II vehicles. Vehicle makes may include but aren't limited to Ford, Chevrolet, Dodge, VW, etc. Anecdotally this code seems to be more commonly seen on Ford/Powerstroke vehicles.
If your OBD-II equipped vehicle has stored a code P215A, it means that the powertrain control module (PCM) has detected a discrepancy between the vehicle output speed sensor and one (or more) of the wheel speed sensors. The vehicle output speed sensor is most frequently called the vehicle speed sensor (VSS).
The output speed sensor and the wheel speed sensor are both intended to detect vehicle speed but each is a component of a separate network. The output speed sensor is part of the powertrain control network and the wheel speed sensor is part of the antilock brake system network.
The output speed sensor is an electromagnetic sensor which is mounted in close proximity to some type of toothed reluctor ring wheel or gear. The reluctor ring is mechanically affixed to an axle, transmission/transfer case output shaft, or driveshaft. The reluctor ring spins in conjunction with the axle. As the reluctor ring teeth pass within thousandths-of-an-inch of the output speed sensor, the magnetic field completes the output speed sensor input circuit. The notches between the reluctor ring teeth create interruptions in the same circuit. These completions/interruptions occur in rapid succession as the vehicle rolls forward. These circuit completions and interruptions create wave form patterns that are received by the PCM (and other controllers) as output speed. As wave form pattern speed increases, estimated vehicle speed increases. Likewise, as the input speed of the wave form slows, estimated vehicle speed decreases. Output speed sensor input voltage signals are compared by various controllers via the controller area network (CAN).
In much the same way as the PCM monitors output speed, the antilock brake control module (ABCM) monitors input data from the wheel speed sensors. Wheel speed sensors are mounted near a reluctor ring on a brake rotor, hub assembly, or differential ring gear. Most OBD-II vehicles are equipped with a four-wheel antilock brake system (ABS) but some applications have a rear-wheel only antilock braking system.
The PCM is constantly monitoring vehicle output speed when the vehicle in moving forward. Individual wheel speed sensor inputs are constantly monitored by the ABCM or electronic brake control module (EBCRM). The two controllers share data via the CAN and compare the signals anytime the vehicle is in motion. If either of the controllers detects a variation between output speed and wheel speed that exceeds the maximum threshold for a set amount of time, a code P215A will be stored and a malfunction indicator lamp (MIL) may be illuminated.
If your OBD-II equipped vehicle has stored a code P215A, it means that the powertrain control module (PCM) has detected a discrepancy between the vehicle output speed sensor and one (or more) of the wheel speed sensors. The vehicle output speed sensor is most frequently called the vehicle speed sensor (VSS).
The output speed sensor and the wheel speed sensor are both intended to detect vehicle speed but each is a component of a separate network. The output speed sensor is part of the powertrain control network and the wheel speed sensor is part of the antilock brake system network.
The output speed sensor is an electromagnetic sensor which is mounted in close proximity to some type of toothed reluctor ring wheel or gear. The reluctor ring is mechanically affixed to an axle, transmission/transfer case output shaft, or driveshaft. The reluctor ring spins in conjunction with the axle. As the reluctor ring teeth pass within thousandths-of-an-inch of the output speed sensor, the magnetic field completes the output speed sensor input circuit. The notches between the reluctor ring teeth create interruptions in the same circuit. These completions/interruptions occur in rapid succession as the vehicle rolls forward. These circuit completions and interruptions create wave form patterns that are received by the PCM (and other controllers) as output speed. As wave form pattern speed increases, estimated vehicle speed increases. Likewise, as the input speed of the wave form slows, estimated vehicle speed decreases. Output speed sensor input voltage signals are compared by various controllers via the controller area network (CAN).
In much the same way as the PCM monitors output speed, the antilock brake control module (ABCM) monitors input data from the wheel speed sensors. Wheel speed sensors are mounted near a reluctor ring on a brake rotor, hub assembly, or differential ring gear. Most OBD-II vehicles are equipped with a four-wheel antilock brake system (ABS) but some applications have a rear-wheel only antilock braking system.
The PCM is constantly monitoring vehicle output speed when the vehicle in moving forward. Individual wheel speed sensor inputs are constantly monitored by the ABCM or electronic brake control module (EBCRM). The two controllers share data via the CAN and compare the signals anytime the vehicle is in motion. If either of the controllers detects a variation between output speed and wheel speed that exceeds the maximum threshold for a set amount of time, a code P215A will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Symptoms P215A
1
Erratic speedometer
2
Inadvertent ABS or traction control system (TCS) activation
3
Irregular transmission shift patterns
4
ABS codes may be stored
5
The ABS may be disabled
Possible Causes P215A
1
Excessive metallic debris on output/wheel speed sensor magnet
2
Defective wheel speed/vehicle speed sensor
3
Cut or damaged wiring or connectors
4
Broken, damaged, or worn reluctor ring teeth
5
Faulty PCM, ABCM, or EBCM
Solutions & Repair Steps P215A
A diagnostic scanner with a built-in oscilloscope, a digital volt/ohmmeter (DVOM), and a source of reliable vehicle information will be needed to diagnose a code P215A.
You will need the vehicle information resource for wiring diagrams, connector face views, connector pin-out charts, diagnostic flow charts, and component testing procedures/specifications. Without this information, a successful diagnosis is impossible.
After performing a visual inspection of system related wiring and connectors, I would continue by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. I like to write this information down as it may be helpful as the diagnostic process unfolds. After that, I clear the codes and test-drive the vehicle to see if the code is reset.
If you have access to some type of oscilloscope: The following procedure applies to the output speed sensor and all individual wheel speed sensors.
Test the output speed sensor and the individual wheel speed sensors:
Test output speed and individual wheel speed reference voltage:
Test output speed sensor and individual wheel speed sensor signal voltage:
If the signal circuit reflected the correct degree of voltage at the sensor connector, use the DVOM to test the output speed sensor and individual wheel speed sensor signal circuits at their respective controller connectors:
If there is an acceptable sensor signal at the sensor connector that is not at the controller connector, you have an open circuit between the controller and the sensor being tested. Suspect controller failure or a programing error only after exhausting all other possibilities.
You will need the vehicle information resource for wiring diagrams, connector face views, connector pin-out charts, diagnostic flow charts, and component testing procedures/specifications. Without this information, a successful diagnosis is impossible.
After performing a visual inspection of system related wiring and connectors, I would continue by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. I like to write this information down as it may be helpful as the diagnostic process unfolds. After that, I clear the codes and test-drive the vehicle to see if the code is reset.
If you have access to some type of oscilloscope: The following procedure applies to the output speed sensor and all individual wheel speed sensors.
Test the output speed sensor and the individual wheel speed sensors:
Test output speed and individual wheel speed reference voltage:
Test output speed sensor and individual wheel speed sensor signal voltage:
If the signal circuit reflected the correct degree of voltage at the sensor connector, use the DVOM to test the output speed sensor and individual wheel speed sensor signal circuits at their respective controller connectors:
If there is an acceptable sensor signal at the sensor connector that is not at the controller connector, you have an open circuit between the controller and the sensor being tested. Suspect controller failure or a programing error only after exhausting all other possibilities.