When your Check Engine Light comes on and an OBD-II scanner reads a P1374 diagnostic code, your car is telling you that the engine management system has lost track of the engine's timing. This matters because the Powertrain Control Module (PCM) relies on the exact relationship between the camshaft and crankshaft to fire the spark plugs and inject fuel. If those sensors do not agree, your engine might hesitate, stall in traffic, or refuse to start altogether.

What exactly does the P1374 code mean?

In most cases, particularly on General Motors vehicles with the 3.8L V6 engine, this code points to a Crankshaft Position (CKP) Sensor to Camshaft Position (CMP) Sensor correlation problem. The PCM monitors the signals from both sensors. The crankshaft sensor tells the computer where the pistons are, while the camshaft sensor tracks the valves. When the timing correlation falls outside the expected range, the computer sets the P1374 trouble code and often limits engine performance to prevent internal damage.

Before tearing into the engine, it helps to understand the specific trigger for your model's P1374 error since definitions can vary slightly between manufacturers. For example, on some Ford models, it might point to an Ignition Control Module (ICM) high-to-low frequency issue instead of a timing correlation.

When will you see this code on your dashboard?

You will usually notice the check engine light illuminating alongside drivability issues. Drivers usually seek out a breakdown of the warning signs associated with this code after noticing their vehicle stuttering at highway speeds. Common symptoms include:

  • Rough idling or shaking at stoplights
  • Hesitation or stumbling during acceleration
  • Engine stalling, especially when coming to a stop
  • Poor fuel economy due to incorrect fuel injection timing
  • Hard starting in the morning

If the correlation is only slightly off, the car might drive completely fine until you hit a specific RPM range. If the signal is lost entirely, the car may enter limp mode to protect the engine.

What usually causes a P1374 trouble code?

A faulty camshaft position sensor is the most frequent culprit. Over time, heat and vibration break down the internal electronics of the sensor. However, wiring damage is just as common. Rodents chewing on wires, or a harness rubbing against a hot exhaust manifold, can cause intermittent signal drops.

To avoid throwing parts at the problem, you should review a deeper look at the mechanical failures that set off this alert before buying anything new. Other known causes include:

  • A cracked or slipping harmonic balancer throwing off the crankshaft signal
  • Excessive timing chain slack
  • Dirt or metal shavings on the magnetic tip of the sensor
  • A corroded wiring harness connector

Common mistakes mechanics make when diagnosing this issue

The most expensive mistake is replacing the PCM without testing the wiring first. Another frequent error is replacing the crankshaft sensor when the code actually relates to the camshaft sensor, just because the crankshaft sensor is sometimes harder to reach.

Mechanics also sometimes ignore the reluctor wheel or interrupter ring. If this metal ring gets bent or accumulates debris, a brand-new sensor will still send distorted signals. You must visually inspect the physical path the sensor reads, not just the electrical resistance.

Practical tips for testing and fixing the issue

Start by connecting a high-quality scan tool to view the live data for both the CMP and CKP sensors. Rev the engine and watch the signal graphs. If the camshaft signal drops out randomly, you know where to focus your attention.

Next, check the wiring harness. Wiggle the wires near the connector while the engine is idling. If the engine suddenly stumbles, you have found a broken wire or loose pin. If you print out a wiring diagram to trace the harness, using a clean typeface like Roboto makes the small text much easier to read under garage lighting.

Always unplug the battery before replacing sensors to clear the Keep Alive Memory (KAM), and use an oscilloscope if live data is inconclusive. A multimeter will check for voltage, but an oscilloscope shows you the actual shape of the digital signal.

Next steps for your vehicle

Before you clear the code and hope it goes away, follow a structured diagnostic path to save time and money.

  1. Scan for all codes: Note if there are secondary codes for misfires or wiring shorts.
  2. Inspect the connectors: Look for green corrosion, pushed-back pins, or brittle wire looms at both the camshaft and crankshaft sensors.
  3. Check the harmonic balancer: Look for separated rubber or misalignment between the inner and outer rings.
  4. Test the sensor resistance: Compare the ohm readings against the factory service manual specifications for your specific vehicle.
  5. Clear and retest: After making a repair, clear the memory and drive the vehicle through a full drive cycle to ensure the code does not return.