P1670 Code: Complete DIY Repair Guide

The P1670 trouble code is a diagnostic code related to the communication between the Powertrain Control Module (PCM) and the Injector Driver Module (IDM) in Ford diesel engines, particularly the 7.3L Power Stroke. This code indicates that the Electronic Feedback (EF) signal from the IDM to the PCM is not being detected, which can lead to various engine performance issues.

Symptoms of P1670 Code

When a vehicle experiences the P1670 code, several symptoms may manifest:

1. Engine cranks but fails to start
2. Intermittent starting issues
3. Rough idling or misfires
4. Reduced engine performance
5. Illuminated Check Engine Light
6. Potential stalling while driving

These symptoms can vary in severity and may not all be present simultaneously. The primary issue stems from the PCM’s inability to receive proper feedback from the IDM, which is crucial for managing fuel injection timing and duration.

Technical Explanation of P1670

The P1670 code specifically relates to the Electronic Feedback (EF) signal in Ford’s Power Stroke diesel engines. This signal is a vital communication link between the IDM and the PCM. The IDM is responsible for controlling the fuel injectors, while the PCM oversees overall engine management.

When functioning correctly, the IDM sends an EF signal to the PCM to confirm that it has received and executed the PCM’s commands for fuel injection timing and duration. This feedback loop ensures precise control over the engine’s fuel delivery system. Additionally, the EF signal transmits diagnostic information about the IDM and fuel injector circuitry to the PCM.

If the PCM fails to detect this EF signal, it triggers the P1670 code. This lack of communication can lead to improper fuel injection, resulting in the various symptoms mentioned earlier.

Step-by-Step Diagnosis of P1670

To diagnose the P1670 code effectively, follow these steps:

1. Connect an OBD-II scanner and verify the P1670 code.
2. Check for any additional codes that may be present, as P1670 can sometimes appear alongside other related codes.
3. Inspect the IDM for visible signs of damage or corrosion.
4. Examine the wiring harness and connectors between the IDM and PCM for any damage, loose connections, or corrosion.
5. Test the continuity of the EF circuit (typically gray/white wire) between the IDM and PCM.
6. Check the IDM fuse and relay for proper operation.
7. Measure the voltage at the IDM connector to ensure it’s receiving proper power.
8. If possible, use a specialized diagnostic tool to monitor IDM communication in real-time.
9. Perform a wiggle test on the wiring harness while the engine is running to check for intermittent connections.
10. If all other tests pass, consider testing the PCM’s ability to communicate with other modules.

Solutions for P1670 Code

Based on the diagnosis results, implement the following solutions:

1. Replace the IDM if it’s found to be faulty. This is often the primary cause of the P1670 code.
2. Repair or replace any damaged wiring in the EF circuit or other related circuits.
3. Clean and secure all electrical connections, particularly those at the IDM and PCM.
4. Replace blown fuses or faulty relays in the IDM circuit.
5. If the PCM is determined to be the cause, it may need reprogramming or replacement.
6. In some cases, updating the PCM software can resolve communication issues.

Warning: Always disconnect the vehicle’s battery before performing any electrical repairs to avoid short circuits or electrical shocks.

Cost Estimates for P1670 Repairs

The cost of repairing a P1670 code can vary significantly depending on the root cause and the vehicle model. Here are some estimated costs:

• IDM replacement: $300 – $800
• Wiring harness repair: $150 – $400
• PCM replacement: $500 – $1000
• Diagnostic fee: $75 – $150

These estimates include both parts and labor. DIY repairs can significantly reduce costs, especially for simpler fixes like cleaning connections or replacing fuses.

Preventing P1670 Code Recurrence

To minimize the chances of encountering the P1670 code in the future:

1. Regularly inspect and clean electrical connections, especially in areas exposed to the elements.
2. Protect the IDM from excessive heat and moisture.
3. Avoid using aftermarket performance tuners that may overload the IDM.
4. Perform regular maintenance as specified in your vehicle’s owner manual.
5. Address any engine performance issues promptly to prevent cascading failures.

When to Seek Professional Help

While many aspects of diagnosing and repairing a P1670 code can be done by experienced DIY mechanics, there are situations where professional assistance is recommended:

• If you lack the necessary diagnostic tools or expertise to safely perform electrical system tests.
• When the issue persists after attempting the common fixes mentioned above.
• If you suspect PCM issues, as reprogramming typically requires specialized equipment.
• When dealing with newer vehicles with more complex electronic systems.

Professional technicians have access to advanced diagnostic tools and manufacturer-specific information that can expedite the repair process and ensure a correct fix.

Conclusion

The P1670 code, while specific to certain Ford diesel engines, represents a common type of communication error in modern vehicles. By understanding the code’s meaning, potential causes, and diagnostic steps, vehicle owners can make informed decisions about repairs. Whether tackling the issue yourself or seeking professional help, addressing the P1670 code promptly is crucial for maintaining optimal engine performance and preventing more severe issues down the road.

Frequently Asked Questions About P1670

• Can I drive my vehicle with a P1670 code?
  While the vehicle may still run, it’s not recommended to drive with this code active. It can lead to poor performance and potential engine damage.
• How often does the IDM typically need replacement?
  IDMs can last the lifetime of the vehicle, but failures are not uncommon after 100,000 miles. Environmental factors and driving conditions can affect longevity.
• Will a P1670 code clear itself?
  Generally, no. The code will remain until the underlying issue is fixed and the code is cleared with a scanner.
• Can a bad battery cause a P1670 code?
  While not a direct cause, a weak battery can lead to voltage fluctuations that may trigger communication errors. Always ensure your battery is in good condition.
• Is the P1670 code specific to Ford vehicles?
  Yes, this specific code is primarily associated with Ford diesel engines, particularly the 7.3L Power Stroke. Other manufacturers may use different codes for similar issues.
• Can weather conditions affect the occurrence of P1670?
  Extreme temperatures and moisture can exacerbate existing wiring or connection issues, potentially triggering the P1670 code.
• How long does it typically take to diagnose and repair a P1670 code?
  Diagnosis can take 1-2 hours, while repairs can range from 30 minutes for simple fixes to several hours for complex issues like IDM or PCM replacement.
• Are aftermarket IDMs reliable for fixing P1670?
  Quality varies among aftermarket parts. OEM or high-quality remanufactured IDMs are generally more reliable, though they may be more expensive.