P0717 - Input Speed Sensor Circuit Low Input

Introduction:

The P0717 diagnostic trouble code (DTC) signals an issue within the input speed sensor (ISS) circuit of your vehicle's automatic transmission. This sensor plays a crucial role in monitoring the rotational speed of the transmission's input shaft, providing vital data to the powertrain control module (PCM) or transmission control module (TCM) for proper shift timing and overall transmission function. When the PCM/TCM detects a low or absent signal from the ISS, it triggers the P0717 code, potentially leading to shifting problems and reduced vehicle performance. Addressing this issue promptly is essential to avoid further damage to the transmission.

Table: P0717 - Input Speed Sensor Circuit Low Input

Detailed Explanations:

Definition:

The P0717 code specifically points to a problem within the Input Speed Sensor (ISS) circuit. The PCM/TCM relies on the ISS to accurately gauge the speed at which the transmission's input shaft is rotating. This information is critical for determining the optimal time to shift gears. When the PCM/TCM detects a consistently low voltage or no signal from the ISS circuit, indicating a significantly lower speed than expected or a complete absence of speed information, it interprets this as a malfunction and triggers the P0717 code. This disrupts the normal shifting patterns of the automatic transmission.

Symptoms:

The symptoms associated with a P0717 code can vary depending on the severity of the problem and the vehicle's specific programming. A lit Check Engine Light is the most consistent symptom. Other common symptoms include erratic shifting, where the transmission shifts inappropriately or at the wrong times. The transmission may also fail to shift into certain gears or may slip during gear changes, resulting in a loss of power. Harsh shifting is another possibility, where gear changes feel abrupt and jarring. In some cases, the vehicle may enter Limp Mode, a safety feature that limits engine power and gear selection to prevent further damage. This can also lead to increased fuel consumption due to the inefficient operation of the transmission. In extreme scenarios, the engine might stall or the transmission could overheat.

Diagnostic Steps:

1. Verify the Code with a Scan Tool: Always confirm the presence of the P0717 code using a reliable OBD-II scan tool. This ensures the code is legitimate and not a misreading.

2. Inspect the Input Speed Sensor and Wiring: Carefully examine the ISS for any signs of physical damage, such as cracks or breaks. Trace the wiring harness connected to the sensor, looking for damaged, frayed, or exposed wires.

3. Check Transmission Fluid Level and Condition: Low or contaminated transmission fluid can interfere with the proper operation of the transmission and its sensors. Check the fluid level according to the vehicle manufacturer's recommendations. Inspect the fluid for signs of burning, discoloration, or the presence of metal particles.

4. Test the Input Speed Sensor: Use a multimeter to measure the sensor's resistance. Compare the reading to the manufacturer's specifications. If the resistance is outside the specified range, the sensor is likely faulty. An oscilloscope can also be used to visually inspect the sensor's output signal while the engine is running.

5. Check for Related DTCs: Look for other diagnostic trouble codes related to the transmission or engine control system. These codes can provide valuable clues about the underlying problem.

6. Diagnose the PCM/TCM: In rare cases, the PCM/TCM itself may be faulty, causing the P0717 code to be triggered incorrectly. Before replacing the PCM/TCM, rule out all other possible causes. This often requires specialized diagnostic equipment and knowledge.

7. Test Circuit Continuity and Resistance: Use a multimeter to check the continuity of the wiring harness between the ISS and the PCM/TCM. Also, measure the resistance of the circuit to identify any shorts or open circuits.

8. Perform a Visual Inspection of the Transmission: Look for any signs of external damage or leaks on the transmission case. Internal mechanical issues within the transmission can sometimes trigger the P0717 code.

Common Mistakes:

A common mistake is replacing the ISS without thoroughly testing the circuit. Often, the sensor itself is not the problem, but rather a wiring or connector issue. Neglecting to check the wiring and connectors can lead to misdiagnosis and unnecessary repairs. Ignoring related DTCs can also hinder the diagnostic process, as these codes may provide valuable insights into the root cause of the problem. Failing to check the transmission fluid level and condition is another oversight, as low or contaminated fluid can contribute to transmission problems. Finally, assuming the PCM/TCM is faulty without proper diagnosis can be an expensive mistake, as these modules are often costly to replace.

Related Codes:

Several other DTCs can be related to the P0717 code, indicating similar or interconnected issues within the transmission system. P0715 (Input/Turbine Speed Sensor Circuit) is a general code indicating a problem with the ISS circuit. P0716 (Input/Turbine Speed Sensor Circuit Range/Performance) suggests that the signal from the ISS is within range but not performing as expected. P0718 (Input/Turbine Speed Sensor Circuit Intermittent) indicates an intermittent problem with the ISS circuit. P0720 (Output Speed Sensor Circuit), P0721 (Output Speed Sensor Circuit Range/Performance), and P0722 (Output Speed Sensor Circuit No Signal) relate to the output speed sensor (OSS), which monitors the speed of the transmission's output shaft. Other transmission-related codes may also be present, depending on the specific problem.

Component Location:

The Input Speed Sensor is typically located on the transmission case, near the input shaft. Its exact location varies depending on the vehicle make and model. Consult your vehicle's repair manual for specific information or search online using your vehicle's year, make, and model along with "Input Speed Sensor Location". It's often found near the bellhousing (where the transmission connects to the engine) or the transmission pump area. The sensor usually has a two- or three-wire connector attached to it.

Testing Procedures:

1. Visual Inspection: Carefully examine the sensor for any physical damage, such as cracks or breaks. Look for signs of corrosion or damage to the sensor's housing.

2. Wiring Inspection: Trace the wiring harness connected to the sensor, looking for damaged, frayed, or exposed wires. Pay close attention to areas where the wiring may be rubbing against other components.

3. Connector Inspection: Ensure the connector is securely attached to the sensor and free of corrosion. Clean the connector terminals with electrical contact cleaner if necessary. Check for bent or broken pins within the connector.

4. Resistance Test: Disconnect the sensor from the wiring harness. Use a multimeter to measure the sensor's resistance between the terminals. Compare the reading to the manufacturer's specifications. A significantly higher or lower resistance than specified indicates a faulty sensor.

5. Signal Test: With the engine running and the transmission in drive, use an oscilloscope to monitor the sensor's output signal. The signal should be a clean, consistent waveform that changes with engine speed. A weak, erratic, or absent signal indicates a problem with the sensor or its circuit.

Repair Strategies:

• Replace the Input Speed Sensor: If the sensor is found to be faulty after testing, replace it with a new, OEM-quality sensor.

• Repair or replace damaged wiring: Repair any damaged, frayed, or exposed wires in the ISS circuit. Use proper splicing techniques and protect the repairs with heat shrink tubing. If the wiring is severely damaged, replace the entire wiring harness section.

• Clean or replace corroded connectors: Clean corroded connector terminals with electrical contact cleaner. If the connector is severely corroded or damaged, replace it with a new connector.

• Reflash or replace the PCM/TCM: If the PCM/TCM is suspected to be faulty, try reflashing it with the latest software. If reflashing does not resolve the problem, the PCM/TCM may need to be replaced. This should be done by a qualified technician.

• Repair internal transmission damage: If internal transmission damage is suspected, the transmission will need to be disassembled and inspected. Repair or replace any damaged components, such as gears, bearings, or seals.

• Add transmission fluid to the correct level: Ensure the transmission fluid level is at the proper level according to the vehicle manufacturer's recommendations. Use the correct type of transmission fluid.

Expected Costs:

The cost of repairing a P0717 code can vary depending on the cause of the problem and the labor rates in your area. The Input Speed Sensor itself typically costs between $30 and $150. Wiring repair can range from $50 to $300, depending on the extent of the damage. Connector replacement can cost between $20 and $100. PCM/TCM reflashing typically costs between $75 and $250. PCM/TCM replacement can be expensive, ranging from $400 to $1200 or more. Transmission repair can cost anywhere from $500 to $3000 or more, depending on the extent of the damage. Labor costs typically range from $75 to $150 per hour. These are just estimates and actual costs may vary significantly.

Frequently Asked Questions:

• What does the P0717 code mean? The P0717 code indicates a problem with the Input Speed Sensor (ISS) circuit, specifically that the PCM/TCM is receiving a low or no signal. This disrupts the transmission's ability to determine the input shaft speed.

• Can I drive my car with a P0717 code? Driving with a P0717 code is not recommended, as it can lead to erratic shifting, transmission slipping, and potential damage to the transmission. It's best to have the problem diagnosed and repaired as soon as possible.

• How do I fix a P0717 code? Fixing a P0717 code involves diagnosing the cause of the problem, which could be a faulty ISS, wiring issues, connector problems, or a PCM/TCM malfunction. Repairing or replacing the affected components will typically resolve the code.

• Is the Input Speed Sensor the same as the Output Speed Sensor? No, the Input Speed Sensor (ISS) monitors the speed of the transmission's input shaft, while the Output Speed Sensor (OSS) monitors the speed of the transmission's output shaft. They serve different functions and are located in different areas of the transmission.

• Can low transmission fluid cause a P0717 code? Yes, low transmission fluid can contribute to a P0717 code, as it can interfere with the proper operation of the transmission and its sensors. Checking and maintaining the correct fluid level is important.

Conclusion:

The P0717 diagnostic trouble code signifies a critical issue within the input speed sensor circuit, directly impacting the automatic transmission's ability to function correctly. Thorough diagnosis, including sensor testing and wiring inspection, is crucial to identifying the root cause and implementing the appropriate repair, preventing further transmission damage.