The error code P0735, often described as “Gear 5 Incorrect Ratio,” signals a problem within your vehicle’s transmission system, specifically concerning its ability to correctly engage or disengage fifth gear. This fault code is triggered when your car’s transmission control module (TCM) detects a discrepancy in the expected gear ratios while attempting to shift into or operate in fifth gear. Understanding the P0735 code is the first step in diagnosing and resolving potential transmission issues, ensuring your vehicle remains in optimal driving condition.
Key Insights into the P0735 Code:
- P0735 Definition: Indicates an issue with the transmission’s capability to accurately shift into fifth gear.
- Symptoms to Watch For: Look out for the check engine light, a decline in fuel economy, and noticeable shifting problems.
- Professional Diagnosis is Key: Addressing P0735 effectively requires a skilled mechanic to properly diagnose and repair the underlying issue.
- Range of Potential Causes: The causes can vary widely, from serious internal transmission failure to simpler wiring issues.
- Timely Action is Essential: Ignoring the P0735 code can lead to more extensive and costly transmission damage.
Understanding the P0735 Code: Gear 5 Incorrect Ratio Explained
The P0735 diagnostic trouble code (DTC) arises when your vehicle’s transmission control module (TCM) identifies an anomaly in the rotational speeds of the input speed sensor and the output speed sensor while the transmission is in, or attempting to shift into, fifth gear. Essentially, the TCM expects a specific ratio between these sensor readings in fifth gear, and when this ratio is not as expected, the P0735 code is logged.
The transmission control module (TCM) is the brain of your automatic transmission system. It utilizes sophisticated sensors and actuators, including shift solenoids, to manage fluid pressure and orchestrate gear changes. When the TCM perceives an incorrect gear ratio in fifth gear, it recognizes a fault and illuminates the check engine light, storing the P0735 code in its memory.
To access this error code and other valuable diagnostic information, mechanics use a scan tool which connects to your vehicle’s OBD-II port. This tool allows them to retrieve stored trouble codes, like P0735, from the TCM, providing a starting point for accurate diagnosis and repair. For any issues related to the P0735 code, seeking the expertise of a certified mechanic and a reputable repair shop is strongly advised. Their expertise ensures proper diagnosis and effective repairs, safeguarding the longevity and performance of your transmission.
Decoding the Root Causes of the P0735 Code
The P0735 error code is not a standalone problem but rather a symptom indicating an underlying issue within the transmission system. Pinpointing the exact cause is crucial for effective repair. Here are some of the common culprits behind the P0735 code:
- Internal Transmission Failure: Significant wear and tear or damage within the transmission, such as worn-out gears, broken components, or clutch issues, can disrupt the correct gear ratios and trigger the P0735 code.
- Malfunctioning PCM or TCM: The Powertrain Control Module (PCM) and, more directly, the Transmission Control Module (TCM) can experience internal failures or software glitches. If either of these modules malfunctions, it can lead to incorrect signals being sent to the transmission, affecting gear shifting.
- Faulty Transmission Valve Body: The valve body is a critical component that controls the flow of transmission fluid to various parts of the transmission. A malfunctioning valve body, due to blockages, worn valves, or solenoid issues within it, can lead to incorrect fluid pressure and, consequently, gear ratio errors.
- Wiring Issues: Electrical problems, including damaged wiring harnesses, corroded connectors, or short circuits in the transmission control system, can disrupt communication between sensors, solenoids, and the TCM. These wiring faults can lead to erratic transmission behavior and the P0735 code.
- Low or Contaminated Transmission Fluid: Transmission fluid is vital for lubrication, cooling, and hydraulic pressure within the transmission. Insufficient fluid levels or contaminated fluid (dirty, old, or with improper viscosity) can impair the transmission’s ability to shift gears smoothly and efficiently, potentially causing the P0735 code.
- Shift Solenoid Failure: Shift solenoids are electromechanical components that control the flow of transmission fluid to engage specific gears based on commands from the TCM. If the shift solenoid responsible for fifth gear malfunctions, it can prevent proper engagement of the gear, leading to the “Gear 5 Incorrect Ratio” error.
Accurate diagnosis is paramount to effectively resolving the P0735 code. A table summarizing these common causes provides a quick reference:
| Cause | Description |
|---|---|
| Internal Transmission Failure | Damage to gears, clutches, or other internal components affecting gear ratios. |
| Malfunctioning PCM/TCM | Electronic control module issues leading to incorrect transmission commands. |
| Faulty Transmission Valve Body | Problems with fluid flow control within the valve body, impacting gear engagement. |
| Wiring Issues | Electrical faults disrupting signals to and from transmission components. |
| Low/Contaminated Fluid | Insufficient or degraded transmission fluid compromising hydraulic pressure and lubrication. |
| Shift Solenoid Failure | Malfunction of the solenoid controlling fluid flow for fifth gear engagement. |
Given the complexity of modern transmissions, diagnosing and repairing the P0735 code is best handled by certified mechanics. They possess the specialized tools, knowledge, and experience to accurately pinpoint the root cause and implement the necessary repairs.
Recognizing the Symptoms of the P0735 Code
When the P0735 code is present, your vehicle will likely exhibit several symptoms that indicate a transmission problem, particularly related to fifth gear operation. Being aware of these symptoms can help you recognize a potential issue early on and seek timely professional help.
1. Check Engine Light Illumination
The most immediate and noticeable symptom is the check engine light turning on. This warning light is designed to alert you to various system malfunctions, and in the case of the P0735 code, it signifies a detected issue within the transmission system. While the check engine light can indicate many problems, when coupled with other symptoms related to shifting, it strongly suggests a transmission fault like P0735.
2. Reduced Fuel Efficiency
Poor fuel economy is another common symptom associated with the P0735 code. When the transmission is unable to correctly shift into or maintain fifth gear, the engine might have to work harder or operate at less efficient RPM ranges to maintain speed. This inefficiency translates to increased fuel consumption. If you observe a sudden and unexplained drop in your vehicle’s gas mileage, especially alongside other symptoms, it could be linked to the P0735 error.
3. Shifting Problems and Irregular Transmission Behavior
Experiencing inability to shift properly is a primary indicator of a P0735 issue. This can manifest in several ways:
- Difficulty shifting into fifth gear: The transmission may hesitate, refuse, or struggle to engage fifth gear.
- Rough or harsh shifting: Gear changes may become jerky or unusually firm, particularly when shifting around fifth gear.
- Slipping out of gear: The transmission might unexpectedly slip out of fifth gear while driving, resulting in a sudden loss of power and change in engine RPM.
- Inconsistent shifting patterns: The automatic transmission may exhibit erratic or unpredictable shifting behavior overall.
If you experience any of these symptoms, especially in combination, it is highly recommended to have your vehicle inspected by a qualified mechanic as soon as possible. Addressing transmission issues promptly can prevent further damage and ensure safe operation of your vehicle.
Diagnosing the P0735 Error Code: A Step-by-Step Approach
Accurately diagnosing the P0735 code requires a systematic approach and often involves specialized tools and expertise. While some basic checks can be performed, a thorough diagnosis is best left to a certified mechanic or transmission specialist.
The cornerstone of diagnosing P0735, and most OBD-II error codes, is the scan tool. This electronic device plugs into the vehicle’s OBD-II port, typically located under the dashboard. When connected, the scan tool can communicate with the vehicle’s computer systems, including the TCM, and retrieve stored Diagnostic Trouble Codes (DTCs), such as P0735. Reading the code provides the initial confirmation of the “Gear 5 Incorrect Ratio” issue.
However, simply reading the code is not enough for a complete diagnosis. A mechanic will typically follow these steps:
- Initial Code Scan and Verification: Use the scan tool to read and document all present DTCs, not just P0735. Clear the codes and perform a test drive to see if P0735 and any related codes reappear. This helps confirm if the code is an intermittent glitch or a persistent problem.
- Visual Inspection: Conduct a thorough visual inspection of the transmission, related wiring, and connectors. Look for any obvious signs of damage, leaks, or loose connections. Check the transmission fluid level and condition. Low or burnt fluid can be a significant indicator of transmission problems.
- Transmission Fluid Check: Examine the transmission fluid’s level and condition. Low fluid should be topped off and the system checked for leaks. Fluid that is dark, smells burnt, or contains debris suggests internal transmission damage or contamination, which could be contributing to the P0735 code.
- Wiring and Electrical Checks: Inspect the wiring harnesses and connectors associated with the transmission control system. Use a multimeter to test for continuity, shorts, and proper voltage at relevant points in the circuit. Pay close attention to wiring related to the shift solenoids and speed sensors.
- Component Testing: Utilize specialized tools and procedures to test individual transmission components. This may include testing the resistance and operation of shift solenoids, checking the input and output speed sensors for proper signals, and assessing the valve body for mechanical or hydraulic faults.
- TCM Data Analysis: Using an advanced scan tool, monitor live data from the TCM while test driving the vehicle. Observe parameters such as input and output speed sensor readings, gear selector position, solenoid commands, and transmission fluid temperature. This real-time data can reveal inconsistencies or malfunctions in the transmission’s operation.
By systematically following these diagnostic steps, a skilled mechanic can accurately pinpoint the root cause of the P0735 code, whether it’s a mechanical failure, electrical problem, or fluid-related issue. This precise diagnosis is crucial for implementing the correct and effective repairs.
Resolving the P0735 Code: Repair Options
Once a thorough diagnosis has identified the underlying cause of the P0735 code, appropriate repairs can be undertaken. The specific repair strategy will depend heavily on the diagnosed issue. Here are some common repair solutions for the P0735 code:
1. Transmission Overhaul or Replacement
If the diagnosis points to internal transmission failure, such as significant wear on gears, damaged clutches, or broken hard parts, a transmission overhaul or replacement might be necessary. An overhaul involves disassembling the transmission, replacing worn or damaged internal components, and rebuilding it. In cases of severe internal damage or high mileage, replacing the entire transmission with a new or remanufactured unit might be a more cost-effective and reliable long-term solution.
2. PCM or TCM Repair/Replacement
If a malfunctioning PCM or TCM is determined to be the cause, these electronic control modules may need to be repaired or replaced. Sometimes, a software update or reprogramming of the module can resolve software glitches. However, in cases of hardware failure, replacing the faulty module is usually required. After replacement, proper programming and configuration of the new module to the vehicle is crucial.
3. Transmission Valve Body Service or Replacement
For issues stemming from a faulty transmission valve body, repair or replacement of the valve body may be necessary. In some cases, cleaning and servicing the valve body, along with replacing individual faulty solenoids or valves within it, can rectify the problem. If the valve body is severely worn or damaged, complete replacement is often the recommended course of action.
4. Wiring and Connector Repair
If wiring issues are identified, the repair will focus on addressing the electrical faults. This may involve repairing damaged wires, replacing corroded connectors, and ensuring proper grounding and connections throughout the transmission control system. Careful attention to detail is necessary to ensure all electrical issues are resolved and that wiring integrity is restored.
5. Transmission Fluid Service
In cases where low or contaminated transmission fluid is the culprit, a transmission fluid change is essential. This involves draining the old fluid, inspecting for leaks, replacing the transmission filter (if applicable), and refilling with the correct type and amount of fresh, high-quality transmission fluid. In some cases, multiple fluid changes or a transmission flush might be recommended to thoroughly clean the system.
6. Shift Solenoid Replacement
If a shift solenoid failure is diagnosed, specifically the solenoid responsible for fifth gear engagement, replacing the faulty solenoid is the solution. Solenoids are typically accessible after dropping the transmission pan or removing the valve body. It’s often recommended to replace related seals or gaskets when replacing solenoids to prevent leaks.
It is crucial to remember that these are general repair options, and the precise repair procedure will vary depending on the specific vehicle make, model, and the exact nature of the diagnosed problem. Consulting a certified mechanic who specializes in transmission repair is strongly advised to ensure accurate and effective resolution of the P0735 code.
Additional Considerations for the P0735 Code
While focusing on the P0735 code, it’s important to be aware of other transmission error codes that may be present or related. A comprehensive diagnostic approach should consider the entire transmission system and not just isolate the P0735 error. Consulting vehicle-specific repair manuals provides valuable detailed information and guidance for diagnosing and repairing transmission issues effectively.
If you lack experience or are uncomfortable working on complex automotive systems, seeking professional assistance from a qualified mechanic is always the best course of action. Attempting repairs without proper knowledge can potentially lead to further damage or complications.
Related Transmission Error Codes:
- P0700 – Transmission Control System Malfunction: A general code indicating a problem within the transmission control system, often appearing alongside more specific codes like P0735.
- P0715 – Input/Turbine Speed Sensor Circuit Malfunction: Indicates an issue with the input speed sensor circuit, which provides crucial data for gear ratio calculations.
- P0720 – Output Speed Sensor Circuit Malfunction: Signals a problem with the output speed sensor circuit, another key sensor for determining gear ratios and transmission operation.
- P0730 – Incorrect Gear Ratio: A more general incorrect gear ratio code, which, unlike P0735, doesn’t specifically point to fifth gear.
Understanding these related codes can provide a broader context when diagnosing transmission issues.
The Role of OBD-II Codes
The P0735 code, along with the other codes mentioned, falls under the umbrella of OBD-II (On-Board Diagnostic) codes. These standardized codes are designed to help mechanics and technicians diagnose vehicle problems efficiently. Using an OBD-II scanner is the first step in retrieving these codes and initiating the diagnostic process. Proper interpretation of OBD-II codes is essential for accurate diagnosis and effective repair strategies.
Conclusion: Addressing the P0735 Code for Transmission Health
In conclusion, the P0735 code, “Gear 5 Incorrect Ratio,” is a significant indicator of a transmission problem that should not be ignored. If you encounter symptoms like the check engine light, reduced fuel economy, or shifting difficulties, it is crucial to investigate the issue promptly.
The potential causes of P0735 are diverse, ranging from internal transmission damage to electronic control module malfunctions, valve body issues, wiring faults, fluid problems, and shift solenoid failures. To accurately diagnose and effectively repair the P0735 code, seeking the expertise of a certified mechanic with specialized knowledge in transmission systems is highly recommended.
For complex cases, especially those requiring in-depth analysis of the vehicle’s electronic control system, professional assistance is indispensable. Proper diagnosis and repair are essential to ensure the continued performance, reliability, and longevity of your vehicle’s transmission. Addressing the P0735 code promptly will help prevent further damage and maintain a smooth and safe driving experience.
Frequently Asked Questions (FAQ) About the P0735 Code
What is the meaning of the P0735 code?
The P0735 code, termed “Gear 5 Incorrect Ratio,” means the vehicle’s transmission is experiencing a problem correctly engaging or operating in fifth gear. This error occurs when the transmission control module (TCM) detects a mismatch in the expected rotational speeds of the input and output speed sensors for fifth gear.
What are the primary causes of the P0735 error code?
Common causes include internal transmission failure, malfunctioning PCM or TCM, faulty transmission valve body, wiring problems, low or contaminated transmission fluid, and shift solenoid failure.
What are the typical symptoms associated with the P0735 code?
The most common symptoms are an illuminated check engine light, poor fuel economy, and noticeable problems with shifting, particularly difficulty shifting into or maintaining fifth gear.
How can the P0735 code be accurately diagnosed?
Diagnosing P0735 typically begins with using a scan tool to read the DTCs from the vehicle’s OBD-II port. However, thorough diagnosis requires a systematic approach by a certified mechanic, including visual inspections, fluid checks, wiring tests, component testing, and potentially analyzing TCM live data.
What are the common repair solutions for the P0735 code?
Repair solutions vary depending on the root cause but may include transmission repair or replacement, PCM/TCM repair or replacement, transmission valve body service or replacement, wiring repair, transmission fluid change, and shift solenoid replacement. Consulting a mechanic for proper diagnosis and repair procedures specific to your vehicle is crucial.
Are there any important notes to consider regarding the P0735 code?
Yes, it’s important to consider other related transmission error codes alongside P0735. A holistic approach to transmission diagnosis is recommended. Always refer to vehicle-specific repair manuals for detailed guidance and seek professional help if you lack the necessary expertise to perform transmission repairs.
What immediate steps should I take if my vehicle displays the P0735 code?
If you encounter the P0735 code, it’s advisable to schedule an appointment with a certified mechanic for diagnosis and repair as soon as possible. The P0735 code indicates a potentially serious transmission issue that requires professional attention to prevent further damage and ensure safe vehicle operation.
