P1739 Code: Complete DIY Repair Guide

The P1739 code is a diagnostic trouble code (DTC) that indicates a problem in the 3rd clutch pressure switch circuit of the transmission system. This code is commonly found in Honda and Acura vehicles, particularly in models from the late 1990s and early 2000s. When this code is triggered, it means that the Powertrain Control Module (PCM) has detected an issue with the electrical signal from the 3rd clutch pressure switch, which is responsible for monitoring the hydraulic pressure in the transmission’s 3rd clutch.

Symptoms of P1739 Code

When the P1739 code is present, vehicle owners may experience several symptoms that can affect the overall performance and drivability of their vehicle. It’s important to note that these symptoms can vary depending on the severity of the issue and the specific vehicle model.

Common symptoms include:

1. Illuminated Check Engine Light (CEL)
2. Transmission shifting problems, especially when engaging 3rd gear
3. Harsh or delayed gear shifts
4. Transmission slipping
5. Reduced fuel efficiency
6. Loss of power during acceleration
7. Vehicle entering “limp mode” or fail-safe operation

In some cases, the vehicle may not exhibit any noticeable symptoms other than the illuminated Check Engine Light. However, it’s crucial to address the issue promptly to prevent potential damage to the transmission system.

Technical Explanation of P1739 Code

The P1739 code is specifically related to the 3rd clutch pressure switch circuit in the transmission. This switch is designed to monitor the hydraulic pressure in the 3rd clutch of the automatic transmission. When the transmission shifts into 3rd gear, the switch should close, sending a signal to the PCM indicating that the proper pressure has been achieved.

The PCM expects to receive a specific voltage signal from the 3rd clutch pressure switch when the transmission is operating in 3rd gear. If the signal falls outside the expected range or is not received at all, the PCM will set the P1739 code and illuminate the Check Engine Light.

The 3rd clutch pressure switch is typically located on the transmission case and is connected to the PCM via a wiring harness. It’s an important component in the transmission control system, as it helps the PCM determine when to engage or disengage the 3rd clutch, ensuring smooth and proper shifting.

Step-by-Step Diagnosis of P1739 Code

To diagnose the P1739 code, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data.
2. Clear the codes and test drive the vehicle to see if the P1739 code returns.
3. If the code returns, check the transmission fluid level and condition. Low or degraded fluid can cause pressure-related issues.
4. Inspect the wiring and connectors associated with the 3rd clutch pressure switch for any signs of damage, corrosion, or loose connections.
5. Using a digital multimeter, check the resistance of the 3rd clutch pressure switch:

• Disconnect the switch connector
• Measure the resistance between the switch terminals
• Compare the readings to the manufacturer’s specifications (typically, the switch should read as an open circuit when unpressurized)

1. Check the voltage at the 3rd clutch pressure switch connector with the ignition on:

• You should see battery voltage on one pin
• The other pin should show ground when the switch is closed (transmission in 3rd gear)

1. If the switch tests good, use a scan tool to monitor the 3rd clutch pressure switch parameter while driving. Observe if the signal changes appropriately as the transmission shifts through the gears.
2. If all tests pass and the code persists, there may be an issue with the PCM or its programming.

Solutions for P1739 Code

Based on the diagnosis results, here are potential solutions for the P1739 code:

1. Replace the 3rd clutch pressure switch if it’s found to be faulty. This is often the most common solution for this code.
2. Repair or replace any damaged wiring or connectors in the 3rd clutch pressure switch circuit.
3. Perform a transmission fluid service, including replacing the fluid and filter if necessary.
4. Update the PCM software if a known issue exists for your specific vehicle model.
5. In rare cases, internal transmission repairs may be necessary if the problem is related to hydraulic pressure issues within the transmission.

Cost Estimates for P1739 Code Repairs

The cost to repair the P1739 code can vary depending on the root cause and the vehicle make and model. Here are some estimated repair costs:

• 3rd clutch pressure switch replacement: $100 – $300
• Wiring repair: $100 – $400
• Transmission fluid service: $150 – $400
• PCM software update: $100 – $200
• Internal transmission repairs: $1,000 – $4,000+

These estimates include both parts and labor costs. DIY repairs can significantly reduce these costs, especially for simpler fixes like replacing the pressure switch or performing a fluid service.

Warnings and Recommendations

Warning: Continuing to drive with the P1739 code present can lead to more severe transmission damage and potentially unsafe driving conditions.

Recommendations:

1. Always check and address transmission-related codes promptly to prevent further damage.
2. Use high-quality replacement parts and transmission fluid that meet or exceed manufacturer specifications.
3. If you’re unsure about performing any diagnostic steps or repairs, consult a professional mechanic or transmission specialist.
4. Keep records of all repairs and maintenance for future reference and to assist in diagnosing recurring issues.
5. Consider having the transmission system thoroughly inspected if you experience frequent transmission-related codes or issues.

In conclusion, the P1739 code, while often indicative of a simple pressure switch issue, can sometimes point to more serious transmission problems. By following this guide, you can diagnose and potentially repair the issue yourself. However, if you’re uncomfortable with any part of the process or if the problem persists after attempting repairs, it’s best to seek the assistance of a qualified automotive technician.

Frequently Asked Questions About P1739

• Can I drive my car with the P1739 code?
  While the vehicle may still operate, it’s not recommended to drive for extended periods with this code present. Doing so could lead to further transmission damage.
• How urgent is it to fix the P1739 code?
  It’s important to address this code as soon as possible. Ignoring it can lead to more severe transmission issues and potentially unsafe driving conditions.
• Will the P1739 code clear itself?
  In most cases, the code will not clear itself. It will need to be addressed and the underlying issue fixed before the code can be cleared permanently.
• Can a bad battery cause the P1739 code?
  While unlikely, a weak battery can cause various electrical issues that might trigger transmission-related codes. However, it’s not a common cause for P1739 specifically.
• How long does it take to replace a 3rd clutch pressure switch?
  For an experienced mechanic, replacing the switch typically takes 1-2 hours. DIY time may vary depending on skill level and vehicle accessibility.
• Is the P1739 code covered under warranty?
  It depends on your vehicle’s age, mileage, and specific warranty terms. Check your warranty documentation or consult with your dealer for coverage information.
• Can a transmission flush fix the P1739 code?
  While a transmission flush can sometimes resolve shifting issues, it’s unlikely to fix a P1739 code on its own if the problem is with the pressure switch or wiring.
• What’s the difference between P1739 and P0739 codes?
  P1739 is a manufacturer-specific code for the 3rd clutch pressure switch circuit, while P0739 is a generic code related to the transmission clutch temperature sensor circuit.