OBD-II Trouble Code Technical Description

Vehicle Speed – Output Shaft Speed Correlation

What does that mean?

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, Chevy / Chevrolet, etc.

If your OBD-II equipped vehicle has stored a code P215B, it means that the powertrain control module (PCM) has detected a discrepancy between the vehicle (output) speed sensor and the output shaft speed sensor.

The vehicle (output) speed sensor and the output shaft speed sensor are both intended to detect vehicle. In the type of system intended to exhibit a code P215B, the vehicle (output) speed sensor is located in the differential and the output shaft speed sensor is situated near the output shaft housing of the transmission (2WD) or transfer case (4WD).

The vehicle (output) speed sensor and the output shaft speed sensor are both electromagnetic sensors which are 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, ring gear, 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 shaft speed sensor, the magnetic field completes the 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 vehicle speed or output shaft speed. As wave form pattern speed increases, estimated vehicle and output shaft speed increases. Likewise, as the input speed of the wave form slows, estimated vehicle or output shaft speed decreases.

The PCM is constantly monitoring vehicle (output) speed and output shaft speed when the vehicle is moving forward. If the PCM detects a variation between the vehicle (output) speed sensor and the output shaft speed sensor that exceeds the maximum threshold (for a set amount of time) a code P215B will be stored and a malfunction indicator lamp (MIL) may be illuminated.

A transmission speed sensor:

What is the severity of this DTC?

The conditions which contribute to a code P215B being stored may cause incorrect speedometer calibration and erratic transmission shifting patterns. The code should be considered severe and addressed as quickly as possible.

What are some of the symptoms of the code?

Symptoms of a P215B diagnostic code may include:

Erratic speedometer

Inadvertent ABS or traction control system (TCS) activation

Irregular transmission shift patterns

ABS codes may be stored

The ABS may be disabled

What are some of the common causes of the code?

Causes for this P215B code may include:

Incorrect final drive gear ratio (differential ring gear and pinion)

Excessive metallic debris on vehicle (output)/output shaft speed sensor magnet

Defective vehicle (output)/output shaft speed sensor

Transmission slippage

Cut or damaged wiring or connectors

Broken, damaged, or worn reluctor ring teeth

Faulty PCM or PCM programming error

What are some P215B diagnostic and troubleshooting steps?

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 P215B.

With a stored P215B, I would make sure that my automatic transmission was full of clean fluid that did not smell burnt. If the transmission was leaking, I would repair the leak and fill it with fluid, then drive it to make sure that it had not undergone mechanical failure.

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.

The easiest and most efficient method for testing live vehicle (output) speed sensor and the output shaft speed sensor data is with an oscilloscope. If you have access to some type of oscilloscope:

Connect the positive test lead of the scope to the signal circuit of the sensor being tested

Select the appropriate voltage setting on the scope (sensor reference is typically 5-voolts)

Connect the negative test lead to a ground (sensor ground or battery ground)

With the drive wheels off the ground and the vehicle secured, run up the drive train while observing the wave form on the scope display

You are looking for an even waveform pattern with no voltage spikes or glitches as you smoothly accelerate/decelerate through all the gears

If inconsistencies are discovered, suspect a defective sensor or a poor electrical connection

Test the vehicle (output) speed sensor and the output shaft speed sensor:

Place the DVOM on the ohms setting and unplug the sensor being tested

Use the test leads to probe the pins of the connector and compare your findings with sensor testing specifications

Sensors which do not comply with specs should be considered faulty

Test vehicle (output) speed sensor and the output shaft speed sensor reference voltage:

With the key on/engine off (KOEO) and the sensor being tested disconnected, probe the reference circuit pin of the sensor connector with the positive test lead of the DVOM

At the same time, the negative test lead of the DVOM should be used to probe the ground pin of the same connector

Reference voltage must be within the specifications provided in your vehicle information resource (usually 5-volts)

Test vehicle (output) speed sensor and the output shaft speed sensor signal voltage:

Reconnect the sensor and probe the signal circuit of the sensor being tested with the positive test lead of the DVOM (negative test lead to sensor ground or known good engine ground)

With the key on and engine running (KOER) and the drive wheels safely secured off the ground, run up the driveline while observing the voltage display on the DVOM

A speed to voltage chart may be found within the vehicle information source. You can use it to determine if the sensor is functioning properly at a variety of speeds

If either of the sensors being tested fail to reflect the appropriate degree of voltage (according to speed) suspect that it is defective.

If the signal circuit reflected the correct degree of voltage at the sensor connector, use the DVOM to test the vehicle (output) speed sensor and the output shaft speed sensor signal circuits at the PCM connector:

Use the positive test lead of the DVOM to probe the appropriate signal circuit at the PCM

The negative test lead should again be grounded

If there is an acceptable sensor signal at the sensor connector that is not at the PCM connector, you have an open circuit between the PCM and the sensor being tested.
Suspect PCM failure or a programing error only after exhausting all other possibilities.

Use the vehicle information source to garner technical service bulletins (TSB) which match the vehicle, symptoms, and stored codes in question. A code which applies to your circumstances may help to develop an accurate diagnosis