P0735 Code: Here's How to Solve It Fast

The P0735 trouble code is a diagnostic trouble code (DTC) that indicates an issue with the transmission system, specifically relating to the incorrect gear ratio in fifth gear. When the transmission control module (TCM) detects that the actual gear ratio does not match the expected ratio for fifth gear, it triggers this code. This discrepancy can lead to various performance issues, including poor acceleration, slipping gears, and reduced fuel efficiency. Understanding the P0735 code is crucial for vehicle owners and DIY mechanics as it can help in diagnosing and addressing potential transmission problems effectively.

P0735 Code Meaning	P0735 Code Common Causes
Gear 5 Incorrect Ratio	Internal transmission failure
Transmission not engaging properly in 5th gear	Malfunctioning PCM (Powertrain Control Module)
Inconsistent RPM readings between input and output sensors	Faulty TCM (Transmission Control Module)
Transmission fluid issues (low or contaminated)	Faulty shift solenoid
Check Engine Light illuminated	Wiring issues or shorts in transmission system

Symptoms of the P0735 Code

When the P0735 code is triggered, several symptoms may manifest, indicating an underlying issue with the transmission system. Recognizing these symptoms early can prevent further damage and costly repairs.

Common Symptoms

• Illuminated Check Engine Light: The most immediate indicator of a problem.
• Delayed Shifting: Difficulty in shifting into fifth gear or delayed engagement when attempting to shift.
• Transmission Slipping: Noticeable slipping during acceleration, which may feel like a loss of power.
• Poor Fuel Economy: A significant drop in fuel efficiency due to improper gear engagement.
• Unusual Noises: Grinding or whining noises when trying to shift into fifth gear.

Technical Explanation of the P0735 Code

The P0735 code is part of a series of codes related to incorrect gear ratios. It specifically indicates that the TCM has detected a discrepancy between the expected and actual gear ratios during operation in fifth gear. This situation arises when there is a failure in one of several components involved in the transmission's operation.

How It Works

The TCM relies on input from various sensors, including:

• Input Speed Sensor: Measures the rotational speed of the input shaft.
• Output Speed Sensor: Monitors the rotational speed of the output shaft.

The TCM compares these readings to determine if the vehicle is operating within its expected parameters. If there is a mismatch—such as when the RPM difference exceeds acceptable limits—the P0735 code is set.

Step-by-Step Diagnosis of the P0735 Code

Diagnosing the P0735 code involves a systematic approach to identify the root cause of the issue. Here’s how you can proceed:

Step 1: Initial Scan

1. Connect an OBD-II Scanner: Plug it into your vehicle’s OBD-II port to retrieve any stored trouble codes.
2. Record All Codes: Note all codes present, especially those related to transmission issues (e.g., P0730-P0736).
3. Clear Codes: Reset the codes and take the vehicle for a test drive to see if they return.

Step 2: Visual Inspection

1. Check Transmission Fluid Level: Ensure that fluid levels are adequate and that there are no leaks.
2. Inspect Wiring and Connectors: Look for any damaged or corroded wires around the TCM and associated sensors.
3. Examine Sensors: Check both input and output speed sensors for proper connection and functionality.

Step 3: Functional Tests

1. Test Drive: Observe how the vehicle shifts through all gears, paying particular attention to fifth gear engagement.
2. Monitor Sensor Readings: Use a scan tool to monitor live data from speed sensors while driving.
3. Check Solenoid Operation: Test shift solenoids for proper function using manufacturer-specific procedures.

Step 4: Advanced Diagnostics

If basic checks do not reveal any issues:

1. Pressure Test: Perform a hydraulic pressure test on the transmission to check for internal leaks.
2. Check TCM Functionality: If all else fails, consider testing or reprogramming the TCM as it may be malfunctioning.
3. Consult Technical Manuals: Refer to specific vehicle repair manuals for detailed diagnostic procedures related to your make and model.

Solution Methods for Fixing the P0735 Code

Once you have diagnosed the issue, implementing appropriate solutions is crucial for resolving the P0735 code effectively.

Common Solutions

• Transmission Fluid Change: If fluid is low or contaminated, replace it with manufacturer-recommended fluid.
• Repair or Replace Wiring: Fix any damaged wiring or connectors found during inspection.
• Replace Faulty Sensors: If either speed sensor is malfunctioning, replace them as needed.
• Shift Solenoid Replacement: If solenoids are found to be faulty, they should be replaced to restore proper shifting functionality.
• Transmission Repair/Replacement: In cases of internal failure, professional repair or complete transmission replacement may be necessary.

Cost Estimates

The cost to diagnose and repair issues related to the P0735 code can vary widely based on location and vehicle type:

• Diagnostic Fees: Typically range from $100 to $150 at most repair shops.
• Fluid Change Costs: Generally between $80 and $150 depending on fluid type and labor costs.
• Sensor Replacement Costs: Usually around $100-$300 per sensor depending on make/model.
• Solenoid Replacement Costs: Typically range from $150 to $500 based on labor charges and parts used.
• Transmission Repair/Replacement Costs: Can range from $1,000 for minor repairs up to $4,000 or more for complete replacements depending on vehicle specifications.

Warnings and Recommendations

When dealing with transmission-related trouble codes like P0735:

• Always consult your vehicle’s service manual for specific diagnostic procedures tailored to your model.
• If you are unsure about any steps in diagnosing or repairing your vehicle, it’s advisable to seek help from a certified mechanic with expertise in transmissions.
• Ignoring symptoms associated with this code can lead to severe damage and costly repairs down the line; timely intervention is critical.

Frequently Asked Questions About P0735

• What does the P0735 code mean?
  The P0735 code indicates a "Gear 5 Incorrect Ratio," signaling that there is an issue with how your transmission engages fifth gear.
• What are common causes of the P0735 code?
  Common causes include internal transmission failure, malfunctioning PCM or TCM, faulty shift solenoids, wiring issues, and low or contaminated transmission fluid.
• What symptoms should I look out for?
  Symptoms include an illuminated check engine light, delayed shifting into fifth gear, slipping transmission, poor fuel economy, and unusual noises during shifting.
• How can I diagnose this trouble code?
  You can diagnose it by using an OBD-II scanner, performing visual inspections of wiring and fluid levels, conducting functional tests on sensors and solenoids.
• What steps should I take if I get this code?
  If you receive this code, check your transmission fluid level first; if low or dirty, change it. Then inspect wiring and sensors before considering more complex repairs.
• Can I drive my car with a P0735 code?
  No, it's not advisable as it can lead to further damage; it's best to address this issue promptly.
• Is professional help necessary?
  Yes, especially if you're unfamiliar with automotive repairs; professional mechanics have specialized tools and knowledge for accurate diagnosis.
• How much will it cost to fix a P0735 code?
  The cost varies widely but can range from $100 for diagnostics up to several thousand dollars for major repairs or replacements.

In conclusion, understanding and addressing the P0735 trouble code is essential for maintaining your vehicle's performance. By recognizing symptoms early and following systematic diagnostic steps, you can effectively troubleshoot this issue. Whether you opt for DIY repairs or seek professional assistance, timely action will help prevent further complications within your vehicle's transmission system.