The P1664 trouble code is an OBD-II diagnostic code that indicates a malfunction in the skip shift upshift lamp control circuit, primarily found in certain vehicles. This code typically arises when the vehicle’s Powertrain Control Module (PCM) detects a discrepancy between the commanded state and the actual state of the skip shift lamp during a self-test. The skip shift feature is designed to improve fuel efficiency by prompting drivers to shift from first to fourth gear under specific conditions. When this system fails, it can lead to various symptoms affecting vehicle performance and drivability.
P1664 Code Meaning | P1664 Code Common Causes |
---|---|
Skip Shift Upshift Lamp Control Circuit Malfunction | Open or shorted circuit in the skip shift lamp control circuit |
Mismatch between commanded and actual state of the skip shift lamp | Faulty PCM or wiring issues |
Defective skip shift lamp bulb | Corroded connectors or damaged wiring harness |
Issues with associated fuses (e.g., GAGES fuse) | Electrical interference or faults in related components |
Symptoms of P1664 Trouble Code
When the P1664 code is triggered, vehicle owners may experience several symptoms, including:
- Check Engine Light: The most common symptom is the illumination of the check engine light on the dashboard.
- Engine Performance Issues: Drivers may notice a decrease in fuel efficiency or unusual engine behavior, such as stalling or misfiring.
- Difficulty Shifting Gears: The skip shift feature may not engage correctly, leading to difficulty in shifting gears smoothly.
- Increased Emissions: A malfunctioning skip shift system can lead to higher emissions due to improper gear usage.
Technical Explanations
The P1664 code is specific to vehicles equipped with a skip shift feature, which is designed to enhance fuel economy by encouraging drivers to skip certain gears during acceleration. The system relies on a lamp that indicates when it is appropriate to shift from first gear directly to fourth gear.
When the PCM detects that the actual state of this lamp does not match its commanded state during a self-test, it triggers the P1664 code. This mismatch can arise from several issues, including:
- Open or Shorted Circuits: If there is an open circuit (disconnected wire) or a short circuit (wire touching another wire or ground), the system cannot function correctly.
- Faulty Components: A defective skip shift bulb or PCM can lead to erroneous readings and trigger the code.
- Wiring Issues: Damaged or corroded wiring can disrupt communication between components, causing failures in the skip shift system.
Step-by-Step Diagnosis
To diagnose the P1664 trouble code effectively, follow these steps:
- Scan for Codes: Use an OBD-II scanner to confirm that P1664 is present and check for any additional codes that may provide more context.
- Inspect Wiring and Connectors:
- Visually inspect the wiring harness associated with the skip shift system for any signs of damage, corrosion, or disconnection.
- Ensure all connectors are securely seated and free from moisture.
- Check Fuses:
- Locate and inspect the GAGES fuse and any other relevant fuses for continuity. Replace any blown fuses.
- Test Skip Shift Lamp:
- Remove the skip shift bulb and test it for continuity using a multimeter. Replace it if it is faulty.
- Perform Circuit Tests:
- Using a multimeter, test for voltage and ground at the skip shift lamp connector while operating the vehicle under conditions that should activate the lamp.
- Check for continuity in the wiring between the PCM and the skip shift lamp.
- Inspect PCM Functionality:
- If all other components check out, consider testing or replacing the PCM as it may be malfunctioning.
Solution Methods
Depending on your findings during diagnosis, here are potential solutions:
- Repair Wiring Issues: If damaged wiring or connectors are found, repair or replace them as necessary.
- Replace Faulty Components: If the skip shift bulb or PCM is defective, replace them with OEM parts to ensure compatibility.
- 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 see if the check engine light returns.
Cost Estimates
The cost of repairing issues related to the P1664 code can vary significantly based on labor rates and parts prices:
- Wiring Repairs: $50 – $200 depending on labor time and materials needed.
- Skip Shift Bulb Replacement: Typically around $10 – $30 for parts.
- PCM Replacement: This can be more costly, ranging from $200 – $1,000 depending on whether you choose a new or refurbished unit plus programming fees if required.
Warnings and Recommendations
- Always disconnect the battery before performing electrical repairs to avoid shorts or further damage.
- If you are uncomfortable diagnosing electrical issues, seek help from a certified technician who has experience with your vehicle make and model.
- Regularly inspect your vehicle’s electrical systems as part of routine maintenance to prevent issues like those associated with P1664 from arising unexpectedly.
Closing Paragraph
The P1664 trouble code indicates an issue with your vehicle’s skip shift upshift lamp control circuit. Understanding its meaning, symptoms, causes, and solutions can empower vehicle owners and DIY mechanics alike to tackle this problem effectively. By following proper diagnostic procedures and addressing any underlying issues promptly, you can restore your vehicle’s performance while avoiding costly repairs down the road.
Frequently Asked Questions About P1664
- What does P1664 mean?
The P1664 code indicates a malfunction in the skip shift upshift lamp control circuit. - Can I drive my car with a P1664 code?
While it may be drivable, ignoring this code could lead to decreased fuel efficiency and performance issues. - How do I clear a P1664 code?
You can clear this code using an OBD-II scanner after performing necessary repairs. - What tools do I need to diagnose P1664?
A multimeter and an OBD-II scanner are essential tools for diagnosing this trouble code. - Is it safe to replace my PCM myself?
If you have experience with automotive electronics, it may be safe; otherwise, consult a professional. - What if my check engine light comes back after repairs?
If it reappears, further diagnosis may be necessary as there could be additional underlying issues. - How much does it cost to fix a P1664 code?
The cost varies widely but typically ranges from $50 for minor repairs to over $1,000 for PCM replacement. - Can other codes trigger alongside P1664?
Yes, related issues may cause multiple codes; it’s essential to address all codes present.