P0735 Code: Complete DIY Repair Guide

The P0735 trouble code is a diagnostic trouble code (DTC) that signifies “Gear 5 Incorrect Ratio.” This code is triggered when the Transmission Control Module (TCM) detects that the transmission is struggling to enter fifth gear or does not enter it correctly. The P0735 code is prevalent in vehicles equipped with automatic transmissions, where the TCM relies on various sensors to monitor and ensure proper operation. If the TCM receives data from these sensors that do not match the expected values, it sets the P0735 code. Addressing this issue promptly is crucial as it can lead to further transmission damage if left unresolved.

Symptoms of P0735 Code

When the P0735 code is triggered, vehicle owners may notice several symptoms, including:

• Illuminated Check Engine Light: The most immediate indication of a problem.
• Poor Fuel Economy: An increase in fuel consumption due to improper gear shifting.
• Difficulty Shifting Gears: The vehicle may struggle to shift into or out of fifth gear.
• Transmission Slipping: A sensation of slipping during acceleration, which can indicate internal issues.
• Unusual Noises: Grinding or clunking noises from the transmission area.

Technical Explanations

The P0735 code indicates that there is a discrepancy between the expected and actual gear ratios in fifth gear. This discrepancy can arise from several factors, including:

• Internal Transmission Failure: Components within the transmission may be worn or damaged, preventing proper engagement of fifth gear.
• Sensor Malfunction: The input speed sensor and output speed sensor work together to relay information about the vehicle’s speed and engine RPM to the TCM. If either sensor fails, it can lead to incorrect readings and trigger the P0735 code.
• Fluid Issues: Low or contaminated transmission fluid can affect hydraulic pressure within the transmission, leading to shifting problems.
• Electrical Problems: Wiring issues, such as short circuits or damaged connectors, can disrupt communication between components.

Step-by-Step Diagnosis

Diagnosing the P0735 code involves a systematic approach:

1. Scan for Codes: Use an OBD-II scanner to confirm that the P0735 code is present and check for any other related codes.
2. Inspect Transmission Fluid: Check the level and condition of the transmission fluid. Look for signs of contamination or burning.
3. Examine Wiring and Connectors: Inspect wiring harnesses connected to the TCM and sensors for damage or corrosion.
4. Test Speed Sensors: Using a multimeter, test both input and output speed sensors for proper resistance and functionality.
5. Check Solenoids: Verify that all shift solenoids are functioning correctly by testing their resistance and operation.
6. Perform a Test Drive: Conduct a test drive while monitoring live data from the TCM to observe how the transmission behaves under load.

Solution Methods

Once you have diagnosed the underlying issue causing the P0735 code, you can proceed with repairs:

1. Transmission Fluid Change

If low or contaminated fluid is identified, changing the transmission fluid and filter may resolve shifting issues.

2. Sensor Replacement

If either speed sensor is faulty, replacing it can restore proper communication with the TCM.

3. Repair Wiring Issues

Fix any damaged wiring or connectors that may be affecting signal transmission between components.

4. Replace Shift Solenoids

If solenoids are malfunctioning, replacing them will help ensure proper gear engagement.

5. Internal Transmission Repair

In cases of severe internal damage, such as worn clutches or gears, a complete rebuild or replacement of the transmission may be necessary.

Cost Estimates

The cost to repair a P0735 code can vary widely based on several factors:

• Fluid Change: $100 – $300
• Sensor Replacement: $150 – $400 per sensor
• Wiring Repairs: $100 – $300 depending on complexity
• Solenoid Replacement: $200 – $600
• Transmission Rebuild/Replacement: $1,500 – $4,000+

These estimates can fluctuate based on labor rates in your region and specific vehicle make and model.

Warnings and Recommendations

• Driving with a P0735 code can lead to further transmission damage; it’s advisable to address this issue promptly.
• If you are not experienced with automotive repairs, seek professional assistance to avoid costly mistakes.
• Always consult your vehicle’s service manual for specific diagnostic procedures and repair guidelines tailored to your make and model.

Closing Paragraph

The P0735 trouble code signifies a serious issue with your vehicle’s transmission system that requires immediate attention. By understanding its symptoms, causes, and solutions, DIY mechanics can take informed steps towards diagnosing and potentially fixing this problem. However, due to the complexity of modern transmissions, involving a certified mechanic for accurate diagnosis and repair is often recommended to ensure long-term reliability and performance of your vehicle.

Frequently Asked Questions About P0735

• What does the P0735 code mean?
  The P0735 code indicates that there is an issue with the automatic transmission not entering fifth gear correctly.
• What are common causes of the P0735 code?
  Common causes include internal transmission failure, malfunctioning PCM/TCM, faulty speed sensors, low fluid levels, wiring issues, and solenoid failures.
• What symptoms should I look for with a P0735 code?
  Symptoms include an illuminated check engine light, poor fuel economy, difficulty shifting gears, slipping transmissions, and unusual noises.
• How can I diagnose a P0735 code?
  You can diagnose it by scanning for codes, inspecting transmission fluid levels and condition, checking wiring and connectors, testing speed sensors and solenoids.
• What are some common solutions for fixing a P0735 code?
  Solutions may include changing transmission fluid, replacing faulty sensors or solenoids, repairing wiring issues, or addressing internal transmission problems.
• Is it safe to drive with a P0735 code?
  No, driving with this code can lead to further damage; it’s best to address it promptly.
• Can I fix a P0735 code myself?
  If you have experience with automotive repairs and access to necessary tools; however, professional help is recommended for complex issues.
• How much will it cost to fix a P0735 code?
  The cost varies widely based on repairs needed but typically ranges from $100 for fluid changes up to $4,000 for complete transmission replacements.