The P1738 trouble code indicates a malfunction in the second clutch pressure switch circuit within an automatic transmission system. This code is specific to certain vehicle makes and models, particularly Honda and Acura, and it typically signifies that the Powertrain Control Module (PCM) has detected an issue with the second clutch pressure switch. This can lead to various transmission problems, including improper shifting and potential damage if not addressed promptly. Understanding the causes, symptoms, and solutions for this code is crucial for vehicle owners and DIY mechanics.
| P1738 Code Meaning | P1738 Code Common Causes |
|---|---|
| Malfunction in the 2nd clutch pressure switch circuit | Faulty 2nd clutch pressure switch |
| Electrical fault in the transmission system | Short or open circuit in wiring |
| PCM detection of abnormal pressure readings | Faulty PCM (rarely required) |
| Improper gear shifting behavior | Contaminated or loose electrical connections |
Symptoms of P1738 Code
When the P1738 code is triggered, drivers may experience several symptoms that can affect vehicle performance:
- Check Engine Light: The most obvious symptom is the illumination of the check engine light on the dashboard.
- Transmission Issues: Drivers may notice rough or harsh shifting, particularly when changing from first to second gear. In some cases, the vehicle may hesitate or jerk during acceleration.
- Reduced Performance: The vehicle may experience a lack of power or responsiveness when accelerating, especially under load.
- Fail-Safe Mode: In severe cases, the transmission may enter a fail-safe mode, limiting performance and preventing normal operation.
Technical Explanation
The P1738 code relates specifically to the second clutch pressure switch within the automatic transmission. This switch is responsible for monitoring hydraulic pressure applied to the second clutch pack, which is essential for smooth gear transitions. If the PCM detects an irregularity in this circuit, it triggers the P1738 code.
How Automatic Transmission Works
Automatic transmissions rely on hydraulic systems to engage and disengage gears. The PCM uses input from various sensors, including pressure switches, to determine when to shift gears. If there is a malfunction in these components, it can lead to improper shifting and potential damage to the transmission.
Step-by-Step Diagnosis
Diagnosing a P1738 trouble code involves several steps:
- Scan for Codes: Use an OBD-II scanner to confirm that P1738 is present. Note any other related codes that may provide additional context.
- Visual Inspection: Check for any visible signs of damage or corrosion in wiring and connectors associated with the second clutch pressure switch.
- Test Voltage Supply: With the ignition on but the engine off, measure voltage at the second clutch pressure switch connector. You should see battery voltage (approximately 12V). If not, there may be an open circuit.
- Continuity Testing: Disconnect both ends of the wiring harness and test for continuity between terminals. There should be no breaks in continuity.
- Check Resistance: Measure resistance across the second clutch pressure switch terminals. A reading significantly different from specifications indicates a faulty switch.
- Inspect PCM Connections: Ensure that all connections to the PCM are secure and free of corrosion.
- Replace Components as Necessary: If tests indicate a faulty switch or wiring issues, replace those components accordingly.
Solution Methods
Addressing a P1738 code typically involves one or more of the following solutions:
- Replace Second Clutch Pressure Switch: If testing confirms that the switch is faulty, replacing it is often a straightforward fix that can restore proper function.
- Repair Wiring Issues: If there are shorts or open circuits found during testing, repairing or replacing damaged wiring can resolve the issue.
- Clear Codes and Test Drive: After repairs are made, clear any stored codes using an OBD-II scanner and take the vehicle for a test drive to ensure that the issue does not return.
- PCM Replacement (if necessary): In rare cases where all other components are functioning correctly but issues persist, replacing the PCM might be required.
Cost Estimates
The cost of repairs related to a P1738 trouble code can vary widely based on several factors:
- Second Clutch Pressure Switch Replacement: Typically ranges from $100 to $300 for parts and labor.
- Wiring Repairs: Costs can vary depending on labor rates but expect anywhere from $50 to $200 based on complexity.
- PCM Replacement: This can be quite expensive, ranging from $500 to $1500 depending on make and model.
Warnings and Recommendations
- Immediate Attention Required: Ignoring a P1738 code can lead to significant transmission damage over time. It’s advisable to address this issue promptly.
- Professional Help Recommended: If you are not comfortable performing electrical diagnostics or repairs, seeking professional assistance is highly recommended.
- Safety Precautions: Always ensure your vehicle is securely supported when working underneath it and take necessary safety precautions when handling electrical components.
Closing Paragraph
The P1738 trouble code signifies an important issue within your vehicle’s transmission system that should not be overlooked. By understanding its meaning, symptoms, and potential solutions, vehicle owners can take proactive steps toward diagnosing and repairing this problem effectively. Whether you choose to tackle these repairs yourself or consult with a professional mechanic, addressing this code promptly will help maintain your vehicle’s performance and reliability.
Frequently Asked Questions About P1738
- What does P1738 mean?
The P1738 code indicates a malfunction in the second clutch pressure switch circuit in an automatic transmission. - What are common symptoms of a P1738 code?
Common symptoms include check engine light illumination, rough shifting during gear changes, and reduced vehicle performance. - Can I drive my car with a P1738 code?
While it may be possible to drive with this code present, it is not recommended as it could lead to further transmission damage. - How do I fix a P1738 trouble code?
Fixing this code typically involves replacing the faulty second clutch pressure switch or repairing any associated wiring issues. - Is replacing the PCM necessary for a P1738 code?
Replacing the PCM is rarely necessary; most issues can be resolved by addressing sensor or wiring problems. - How much does it cost to repair a P1738 code?
The cost can range from $100 to $1500 depending on whether you need a simple switch replacement or a PCM replacement. - What tools do I need to diagnose a P1738 code?
You will need an OBD-II scanner, multimeter for voltage testing, and basic hand tools for any repairs. - Should I attempt repairs myself?
If you have basic automotive knowledge and tools, you may attempt repairs; otherwise, it’s best to consult a professional mechanic.