P1722 Code: Complete DIY Repair Guide

The P1722 trouble code is a manufacturer-specific diagnostic code that typically indicates an issue with the vehicle speed sensor circuit or signal. This code is commonly found in Nissan vehicles but can also appear in other makes. When the engine control module (ECM) or transmission control module (TCM) detects an abnormal or inconsistent speed signal, it will trigger the P1722 code and potentially cause drivability issues.

Faulty Vehicle Speed Sensor

The vehicle speed sensor (VSS) is a crucial component that measures the rotational speed of the transmission output shaft or wheel and sends this information to the ECM and TCM. When this sensor fails, it can lead to various drivability issues and trigger the P1722 code.

Symptoms:

• Erratic speedometer readings
• Cruise control malfunction
• Harsh or delayed shifting
• Check Engine Light illumination

Technical Explanation:
The VSS uses either a magnetic pickup or Hall effect sensor to generate a signal based on the rotation of a toothed wheel. This signal is then converted into a digital format that the ECM and TCM can interpret. A faulty sensor may produce an inconsistent or no signal at all.

Step-by-step Diagnosis:

1. Locate the vehicle speed sensor (usually near the transmission output shaft or rear differential).
2. Inspect the sensor and its wiring for visible damage or corrosion.
3. Use a multimeter to check the sensor’s resistance (refer to the vehicle’s service manual for specifications).
4. If possible, use an oscilloscope to observe the sensor’s output signal while the vehicle is in motion.
5. Compare the readings to the manufacturer’s specifications.

Solution:
If the VSS is determined to be faulty, it will need to be replaced. This is often a straightforward process that can be completed by a DIY mechanic with basic tools.

Cost Estimate:

• VSS replacement part: $50 – $200
• Professional labor: $50 – $150

Warning: Ensure the vehicle is safely supported and the transmission is cool before attempting any work near it.

Damaged Wiring or Connectors

Wiring issues are a common cause of the P1722 code. Over time, wires can become frayed, corroded, or damaged, leading to intermittent or complete signal loss from the VSS to the ECM or TCM.

Symptoms:

• Intermittent speedometer operation
• Sporadic transmission shifting issues
• Check Engine Light flickering on and off

Technical Explanation:
The VSS relies on a clean, consistent electrical signal to function properly. Any interruption or degradation of this signal due to wiring problems can cause the ECM or TCM to misinterpret the vehicle’s speed, triggering the P1722 code.

Step-by-step Diagnosis:

1. Visually inspect the wiring harness from the VSS to the ECM/TCM for any signs of damage.
2. Check all relevant connectors for corrosion, bent pins, or loose connections.
3. Use a multimeter to perform a continuity test on the VSS wiring.
4. Check for proper voltage at the VSS connector when the ignition is on.
5. Perform a wiggle test on the wiring while monitoring for changes in signal output.

Solution:
Depending on the extent of the damage, solutions may range from cleaning and reseating connectors to repairing or replacing sections of the wiring harness.

Cost Estimate:

• Wire repair kit: $10 – $30
• Professional wiring repair: $100 – $300

Recommendation: If you’re not comfortable working with automotive electrical systems, it’s best to consult a professional to avoid causing further damage.

Transmission Control Module Communication Error

In some cases, the P1722 code may be triggered by a communication error between the TCM and other vehicle systems, rather than a direct sensor or wiring issue.

Symptoms:

• Multiple transmission-related codes
• Erratic transmission behavior
• Loss of certain transmission functions

Technical Explanation:
Modern vehicles rely on complex communication networks between various control modules. If the TCM fails to communicate properly with the ECM or other modules, it may interpret this as a speed signal issue and set the P1722 code.

Step-by-step Diagnosis:

1. Use a high-quality OBD-II scanner to check for additional transmission-related codes.
2. Perform a module communication test using a scan tool with bi-directional control capabilities.
3. Check the power and ground connections to the TCM.
4. Inspect the CAN bus wiring for any signs of damage or interference.
5. Verify that the TCM software is up to date.

Solution:
Solutions can range from updating TCM software to replacing a faulty module. In some cases, repairing communication wiring may resolve the issue.

Cost Estimate:

• TCM software update: $50 – $150
• TCM replacement: $300 – $1000
• Professional diagnosis and repair: $100 – $200

Warning: TCM replacement and programming should typically be performed by a professional to ensure proper calibration and functionality.

ABS System Interference

In some vehicles, the ABS system provides wheel speed information to the ECM and TCM. If an ABS wheel speed sensor is faulty, it can cause the P1722 code to appear.

Symptoms:

• ABS light illumination along with the Check Engine Light
• Inconsistent speedometer readings
• Traction control system malfunction

Technical Explanation:
The ABS system uses individual wheel speed sensors to monitor the rotation of each wheel. This information is used not only for anti-lock braking but also to provide vehicle speed data to other systems. A malfunctioning ABS sensor can send incorrect speed signals, triggering the P1722 code.

Step-by-step Diagnosis:

1. Check for any ABS-related codes using an OBD-II scanner.
2. Inspect each wheel speed sensor and its wiring for damage or contamination.
3. Use a multimeter to check the resistance of each ABS wheel speed sensor.
4. If possible, use a scan tool to observe live data from the ABS sensors while driving.
5. Compare the readings from all four wheels to identify any discrepancies.

Solution:
Depending on the diagnosis, solutions may include cleaning the ABS sensors, repairing wiring, or replacing faulty sensors.

Cost Estimate:

• ABS wheel speed sensor: $50 – $200 per sensor
• Professional ABS system diagnosis: $80 – $150

Recommendation: When working on ABS components, be careful not to damage the sensitive magnetic sensors or trigger the ABS module.

Low Transmission Fluid

While less common, low transmission fluid levels can sometimes trigger the P1722 code, especially if the low fluid condition affects the operation of the vehicle speed sensor or internal transmission components.

Symptoms:

• Slipping transmission
• Delayed or harsh shifting
• Unusual transmission noises
• Overheating transmission

Technical Explanation:
Transmission fluid serves multiple purposes, including lubrication, hydraulic pressure for shifting, and cooling. Low fluid levels can cause erratic transmission operation, which may affect speed sensor readings or cause internal damage that triggers the P1722 code.

Step-by-step Diagnosis:

1. Check the transmission fluid level with the engine running and warmed up.
2. Inspect the quality and color of the transmission fluid.
3. Look for signs of transmission fluid leaks under the vehicle.
4. If the fluid level is low, add the correct type of fluid to the proper level.
5. Test drive the vehicle to see if the code clears and symptoms resolve.

Solution:
If low fluid is the cause, simply adding the correct type and amount of transmission fluid may resolve the issue. However, it’s crucial to identify and repair any leaks to prevent future problems.

Cost Estimate:

• Transmission fluid: $20 – $60
• Professional transmission service: $100 – $200
• Transmission leak repair: $150 – $500 (varies widely depending on the source of the leak)

Warning: Always use the transmission fluid specified by your vehicle manufacturer. Using the wrong type can cause severe transmission damage.

Closing Thoughts

The P1722 code, while often related to the vehicle speed sensor or its circuit, can have multiple causes ranging from simple wiring issues to more complex transmission problems. DIY mechanics can often diagnose and repair simpler issues like sensor replacement or wiring repairs. However, for more complex problems involving the transmission control module or internal transmission components, professional assistance may be necessary.

Always start with the simplest and most likely causes, such as checking connections and fluid levels, before moving on to more complex diagnoses. If you’re unsure about any step in the diagnostic or repair process, don’t hesitate to consult a professional mechanic. Proper diagnosis and repair of the P1722 code are crucial for maintaining the safety and reliability of your vehicle’s transmission system.

Frequently Asked Questions About P1722

• Can I drive my car with the P1722 code?
  While you may be able to drive short distances, it’s not recommended. The code indicates a problem that could affect transmission operation and potentially cause further damage.
• Will the P1722 code clear itself?
  In some cases, if the issue is intermittent, the code may clear itself. However, this doesn’t mean the problem is resolved, and the code will likely return if the underlying issue isn’t addressed.
• How much does it typically cost to fix a P1722 code?
  Costs can vary widely, from $50 for a simple sensor replacement to over $1000 for major transmission repairs. An accurate estimate requires proper diagnosis of the specific cause.
• Can a bad battery cause a P1722 code?
  While uncommon, a weak battery can cause various electrical issues that might trigger the P1722 code. However, this is usually accompanied by other electrical symptoms and codes.
• Is the P1722 code related to the Check Engine Light?
  Yes, the P1722 code will typically trigger the Check Engine Light. In some vehicles, it may also cause the transmission warning light to illuminate.
• Can I clear the P1722 code with an OBD-II scanner?
  You can clear the code, but if the underlying issue isn’t resolved, it will likely return. It’s best to diagnose and fix the problem before clearing the code.
• Does the P1722 code affect fuel economy?
  It can, especially if the code is causing the transmission to operate inefficiently or if the vehicle is stuck in a specific gear due to the error.
• Is the P1722 code covered under warranty?
  This depends on your specific warranty coverage and the cause of the code. Many powertrain warranties would cover issues related to this code, but it’s best to check with your dealer or warranty provider.