P1399 Ford: Understanding, Diagnosing, and Resolving This Trouble Code

The P1399 Ford code is a generic On-Board Diagnostic (OBD-II) code that indicates an intermittent problem with the Camshaft Position Sensor (CMP) or the Crankshaft Position Sensor (CKP). Specifically for Ford vehicles, this code is often associated with an intermittent loss of signal from one of these sensors, which are essential for proper engine operation. Understanding the meaning of this code, its symptoms, and the steps to resolve it is crucial for any owner or mechanic facing this issue.

What is the P1399 Trouble Code on a Ford?

The P1399 Ford code literally translates to “Intermittent CMP or CKP Signal Loss.” Your vehicle’s Powertrain Control Module (PCM) continuously monitors the signals sent by the Camshaft Position Sensor (CMP) and the Crankshaft Position Sensor (CKP). These two signals must be perfectly synchronized for the PCM to accurately calculate ignition timing and fuel injection. When the PCM detects a disparity or intermittent interruption in the correlation between these two signals, it stores the P1399 Ford code and illuminates the Malfunction Indicator Lamp (MIL) on the dashboard.

Common Symptoms of the P1399 Code

Symptoms associated with the P1399 Ford code can vary in intensity and may appear and disappear randomly, making diagnosis sometimes tricky. The most frequently observed signs are:

• Starting Problems: The engine may have difficulty starting, require multiple key turns, or sometimes not start at all.
• Irregular Idle: The engine may stall at idle or have a very unstable and rough idle.
• Loss of Power and Misfires: A noticeable loss of power during acceleration, accompanied by jerking or misfiring, especially under load.
• Malfunction Indicator Lamp (MIL): The Check Engine light comes on, often intermittently, in conjunction with other symptoms.
• Increased Fuel Consumption: Poor timing leads to inefficient combustion.

Possible Causes of the P1399 Code on a Ford

Several factors can cause the P1399 Ford code to appear. A methodical investigation is necessary to identify the root cause.

• Faulty Camshaft Position Sensor (CMP): This is the most common cause. The sensor itself may be defective or producing an intermittent signal.
• Faulty Crankshaft Position Sensor (CKP): Although less common as a primary cause for this specific code, a defective CKP can cause the same problem.
• Wiring or Connector Issue: Frayed, corroded, loose, or shorted wires between the sensor and the PCM are a very common cause of intermittency.
• Damaged Reluctor Wheel (Trigger Wheel): The toothed wheel on the camshaft or crankshaft that passes by the sensor may be damaged, dirty, or loose.
• PCM Problem: Although rare, a faulty PCM module may misinterpret correct signals from the sensors.

Step-by-Step Diagnostic Procedure

It is imperative to proceed logically to correctly diagnose a P1399 Ford code.

1. Visual Inspection: Start with a thorough inspection of all wiring and connectors associated with the CMP and CKP sensors. Look for any signs of damage, corrosion, burning, or loose connections. Remember to check the wiring harness near hot or moving parts.

2. Live Data Reading: Using an advanced scan tool, observe the live data from the CMP and CKP sensors while you crank the engine and gently shake the wiring. Look for any intermittent drop or anomaly in the signal.

3. Electrical Tests: Use a multimeter to check the power supply and ground of the CMP sensor. Also test the sensor signal; it should produce an alternating current (AC) voltage that fluctuates when the engine is cranking/running.

4. Reluctor Wheel Inspection: If possible, visually inspect the reluctor wheel on the camshaft to ensure it is not cracked, has no missing teeth, and is securely fastened.

Repair Solutions and Tips

Once the cause is identified, the repair can be undertaken.

• Replace the Faulty Sensor: If tests point to a faulty CMP or CKP sensor, replace it with an OEM quality or equivalent part.
• Repair the Wiring: For any wiring issues, repair or replace the damaged wires. Ensure all connectors are clean, secure, and sealed.
• Clean the Reluctor Wheel: Thoroughly clean the reluctor wheel of any debris or metallic deposits.
• Clear the Code: After the repair, clear the code with your scan tool and perform a road test to ensure the P1399 Ford fault does not return.

Ignoring the P1399 Ford code can lead to more severe driving problems, catalytic converter overheating due to rich combustion, and potentially long-term engine damage. Accurate diagnosis is the key to an economical and effective repair.