P1399 Cadillac: Code Breakdown and Troubleshooting Guide

The P1399 Cadillac code is a manufacturer-specific error code indicating an intermittent problem with the Variable Valve Timing (VVT) system or its circuit. Primarily found on models equipped with Northstar and other engines, this code is often related to the camshaft position sensor (cam sensor). While it may seem alarming, a methodical diagnostic approach can often identify and resolve the issue without exorbitant costs. This article guides you through the causes, symptoms, and solutions to get your vehicle back in perfect working order.

What Does the P1399 Trouble Code Mean on a Cadillac?

The generic OBD-II code P1399 translates to “Intermittent Camshaft (CMP) / Crankshaft Position (CKP) Sensor Fault.” In simple terms, your Cadillac’s Powertrain Control Module (PCM) has detected an inconsistency or loss of signal between the camshaft position sensor and the crankshaft position sensor. These two sensors work in perfect harmony to determine the precise timing for ignition and fuel injection. An erratic signal from one of them disrupts this synchronization, triggering the P1399 Cadillac code and illuminating the Malfunction Indicator Lamp (MIL) on your dashboard.

Common Symptoms of the P1399 Code

When this fault appears, you may observe one or more of the following symptoms:

• Engine shaking or misfiring: Loss of synchronization leads to inefficient combustion.
• Difficulty starting: The PCM struggles to determine piston position to initiate the starting sequence.
• Irregular idle speed: The engine may stall or have a very rough idle.
• Noticeable decrease in performance and power: The car lacks responsiveness and seems to be lacking power.
• Abnormally high fuel consumption: Poor timing makes combustion less efficient.

Possible Causes of the P1399 Code on a Cadillac

Several components can be the source of this problem. It is crucial to investigate them in a logical order.

• Faulty camshaft position sensor: This is the most common cause. The sensor itself, its electrical connector, or its wiring may be damaged, corroded, or defective.
• Wiring or connector problem: Frayed, shorted, or open wires between the sensor and the PCM can cause an intermittent signal.
• Poor sensor power supply voltage or ground: The sensor requires a reference voltage (usually 5V or 12V) and a good ground to function properly.
• Mechanical problem with the camshaft target: The toothed rotor (or tone wheel) that the sensor reads may be damaged or dirty.
• Problem with the crankshaft position sensor (CKP): Although the code often points to the CMP, a failing CKP can also skew the diagnosis.
• Mechanical timing issue with the camshafts: In rare cases, a slightly loose timing chain or a faulty tensioner may be the cause.

Diagnostic Procedure and Solutions

Before replacing expensive parts, follow these diagnostic steps.

1. Visual Inspection

Start with a thorough inspection. Locate the camshaft position sensor (usually located at the front or rear of the cylinder head). Check its connector: is it properly plugged in? Are there any signs of corrosion, oxidation, or damage? Visually inspect the wiring along its entire length for any potential chafing, burns, or cuts.

2. Electrical Testing of the Sensor and Its Circuit

Using a digital multimeter, check the sensor’s power supply voltage (consult the repair manual for values specific to your model). Also test the integrity of the ground. Finally, measure the sensor’s output signal; it should vary when you crank the engine. A flat or absent signal indicates a faulty sensor.

3. Sensor Replacement

If your tests point to a faulty sensor, proceed with its replacement. Always use quality OEM or good quality aftermarket parts. Remember to clear the error codes with an OBD-II scanner after replacement to verify that the P1399 Cadillac fault does not return.

4. Further Investigation

If the problem persists after replacing the sensor, the next step is to mechanically inspect the camshaft target (often requiring disassembly of parts) and meticulously check the wiring all the way to the PCM using an electrical diagram. In the most complex cases, the intervention of a Cadillac specialist mechanic may be necessary.

Conclusion

The P1399 Cadillac code is not a foregone conclusion. Although it can cause significant inconvenience, it is often a symptom of an accessible and replaceable component. By following a logical diagnostic approach, starting with the simplest checks (connectors, wiring), you have a strong chance of resolving the issue and regaining the pleasure of driving your Cadillac with peace of mind. Do not ignore this code, as prolonged operation with this fault can, over time, damage the catalytic converter or other engine components.