P0728 Engine Speed ​​Input Circuit Intermittent

P0728 – OBD-II Trouble Code Technical Description

Engine speed input circuit intermittent

What does the fault code mean P0728?

Code P0728 is a general transmission-related diagnostic trouble code (DTC) that can occur on vehicles equipped with the OBD-II system (including Nissan, Ford, GM, Chevrolet, Dodge, Jeep, GMC, VW, Toyota, and others). ). Although the code is general, repair methods may vary depending on the make and model of the vehicle.

Code P0728 indicates that the powertrain control module (PCM) has detected an intermittent input voltage signal from the engine speed sensor. This sensor may also be called a transmission input speed sensor. The causes of the P0728 code can be either mechanical or electrical.

The engine speed sensor is usually located in the transmission housing near the front of the input shaft. It is equipped with a rubber O-ring that provides a seal with the gearbox housing. When removing the sensor from the housing, be careful as there may be hot transmission fluid inside.

A permanently installed electromagnetic Hall sensor is the basis for the operation of the engine speed sensor. It is positioned so that a gear mounted on the transmission input shaft passes directly past the magnetic tip of the sensor. As the input shaft rotates, the magnetic ring also rotates. The raised areas of the teeth on this ring are used to electromagnetically complete the engine speed input circuit, and the depressed areas between the teeth break this circuit. This results in a signal with changes in frequency and voltage, which the PCM recognizes as engine speed.

Code P0728 is stored and the MIL may illuminate if the PCM detects an intermittent or unstable signal from the engine speed sensor under specified conditions and for a specified period of time. This may cause the transmission control module (TCM) or PCM to go into limp mode.

Related codes associated with the engine speed input circuit include:

• P0725: Engine Speed ​​Input Circuit Malfunction
• P0726: Engine Speed ​​Input Circuit Range/Performance
• P0727: Engine Speed ​​Input Circuit No Signal

The P0728 code should be repaired immediately as ignoring it can cause serious transmission damage and driving problems. It may be accompanied by the following symptoms:

• Sudden or chaotic automatic transmission shifts (switching to no-load mode).
• Lack of gear shifting or random gear shifting.
• Faulty or malfunctioning speedometer and odometer.
• Faulty or malfunctioning tachometer.
• Wheel spin or gear delay.
• Possible presence of additional codes related to transmission speed.

To resolve the P0728 code, it is recommended to diagnose, replace the faulty components (both sensor and wiring) and, if necessary, calibrate the sensor in accordance with the manufacturer's recommendations. In case of insufficient skills or uncertainty about the cause of the malfunction, it is recommended to contact a qualified mechanic or garage.

Possible reasons

Possible causes of a P0728 code include:

1. Open or shorted wires and/or connectors of the engine speed input circuit.
2. Excessive metal deposits on the magnetic tip of the sensor.
3. The engine speed input sensor or transmission output speed sensor is faulty.
4. The resistance ring of the engine speed sensor is damaged or worn.

In most cases, the P0728 code appears when the engine input speed sensor or transmission output speed sensor is faulty.

Other possible reasons include:

1. Shorted, damaged or broken electrical components in the engine speed circuit.
2. Faulty shift solenoid.
3. Faulty engine sensors, such as the engine temperature sensor or other control sensors.
4. The crankshaft or camshaft position sensor is faulty.
5. Faulty electrical components in the crankshaft sensor circuit.
6. Restricted transmission fluid flow due to contaminated fluid.
7. Valve body is faulty.

These reasons may be the source of the P0728 code and require diagnosis and possible repair to correct the problem.

What are the symptoms of a fault code? P0728?

When the P0728 code appears, drivers may notice the following symptoms:

• Hard gear shifting
• Inability to shift into other gears or hesitation when shifting
• Reduced fuel consumption
• Fluctuating or faulty speedometer
• stalled engine
• Incorrect engine operation
• Check engine light on

A stored P0728 code should be considered serious as it may indicate damage to the transmission and drivability problems that may occur. In addition to these symptoms, additional baud rate codes may also be stored, highlighting the importance of promptly diagnosing and repairing this problem.

How to diagnose a fault code P0728?

When diagnosing a P0728 code, a mechanic should follow these steps:

1. Checking the level and condition of the transmission fluid: The first step is to check the level and condition of the transmission fluid. If the level is low or the fluid is contaminated, it should be replaced and leaks checked and repaired.
2. Visual inspection of wires and connectors: The mechanic should carefully inspect all electrical wires, connectors, and harnesses for damage, corrosion, or loose connections. Any problems found must be corrected.
3. Using the diagnostic scanner: Connecting a diagnostic scanner to the vehicle will allow the mechanic to obtain stored codes and freeze frame data. This information may be useful for further diagnosis.
4. Checking the engine speed input sensor: If the problem persists after inspecting the wires and fluid, a mechanic should check the condition of the engine speed input sensor according to the manufacturer's recommendations. If the sensor does not meet specifications, it should be replaced.
5. Checking the engine speed sensor input signal/circuit: Additionally, the mechanic should check the engine speed sensor signal and the condition of the system circuits. This will help identify faults in electrical components.

Once all necessary repairs have been completed, the P0728 code should be cleared from the PCM. If it is returned, the mechanic should continue the diagnosis, ruling out the other potential faults listed in the previous message and manually checking each component to ensure it meets the manufacturer's specifications.

Diagnostic errors

COMMON ERRORS WHEN DIAGNOSING CODE P0728:

When diagnosing code P0728, the following common errors may occur:

1. Incorrect problem identification: Many technicians may misinterpret this code as a problem with the engine, transmission, fuel system, or other components, which can lead to unnecessary repairs.
2. Replacing the speed sensor without first checking: A common mistake is to replace the vehicle speed sensor before conducting a detailed diagnosis of the electrical components or the condition of the transmission fluid.
3. Insufficient testing of electrical components: Skipping a detailed inspection of electrical components and wiring may result in undiagnosed problems.
4. Ignoring the condition of the transmission fluid: Transmission fluid condition and level are often ignored, although they may be the cause of the P0728 code.
5. Unreasonable replacement of parts: In some cases, mechanics may replace parts without proper testing or justification, which can be expensive and unnecessary.

It is important to conduct a comprehensive diagnosis based on knowledge and understanding of the system’s operation in order to avoid unnecessary costs and repairs.

How serious is the fault code? P0728?

Trouble code P0728 is serious because it indicates a problem with the engine speed sensor or transmission output speed sensor. These sensors play an important role in the proper operation of the transmission and control of vehicle speed.

The severity of the problem depends on the specific symptoms and how the car reacts to the problem. In some cases, this can result in harsh gear shifts, inability to shift, or other transmission problems.

In addition to transmission problems, code P0728 can also affect other vehicle systems such as the speedometer, tachometer, and even the engine. Therefore, it is recommended to resolve this issue immediately to avoid further damage and ensure reliable vehicle performance.

What repair will help eliminate the code? P0728?

The following repairs may be required to resolve DTC P0728:

1. Check and replace the engine speed sensor (transmission input speed sensor) if a malfunction is detected.
2. Check and replace the transmission output speed sensor if it is suspected to be faulty.
3. Check and repair wiring, connectors and electrical components in the engine speed circuit if problems are identified in the electrical connections.
4. Checking the transmission fluid and, if necessary, replacing it. If the transmission fluid is contaminated or has problems, it can cause a P0728 code.
5. Check the valve body and transmission cooler for leaks and damage.
6. Check the engine management system, including engine temperature sensors and others, as faults in these systems can also cause P0728.
7. After repair work has been carried out, trouble code P0728 must be reset using a diagnostic scanner.

The exact scope of repair work will depend on the specific cause identified during the diagnostic process. It is recommended that you contact a qualified mechanic or auto repair shop for detailed diagnostics and troubleshooting.

What is P0728 Engine Code [Quick Guide]

P0728 – Brand-specific information

Code P0728 – No signal from the engine speed sensor (transmission input speed sensor). This code can be applied to various brands of vehicles equipped with OBD-II. Here are some examples of brands and their decodings:

1. Nissan: No engine speed sensor signal.
2. Ford: No engine speed sensor signal.
3. GM (Chevrolet, GMC, Cadillac, etc.): No engine speed sensor signal.
4. Dodge: No engine speed sensor signal.
5. Jeep: No engine speed sensor signal.
6. Volkswagen (VW): No engine speed sensor signal.
7. Toyota: No engine speed sensor signal.

Each manufacturer may provide more specific information about the P0728 code for their specific models, so it is recommended that you contact your dealer or official source for more detailed information about your specific vehicle make and model.