Engine Light Cam Shaft Positions Sensor

P0340 Camshaft Position (CMP) Circuit Malfunction

IMO, the key to understand the P0340 DTC is the words “Circuit Malfunction”. Since the sensor itself has been replaced, this leaves a wiring fault as the next most logical step. Look for any break in the wires. Chaffing. What about the connector itself? Is it intact? Are the pins in place? Any damage at all to the connector?

The wiring diagram has been included for reference. Unless you can spot an obvious reason for the fault, some very detailed wiring tests will have to be done. The wiring diagram will help.

A source of electrical interference could be from a bad alternator diode. Have the alternator tested for AC ripple. Very simple test and will rule out a very real possibility.

Another long shot is the radio interference capacitors. Have they been removed/altered?

P0340 - Camshaft Position (CMP) Sensor Circuit Malfunction

The test fails when the PCM can no longer detect the signal from the CMP sensor.
• CMP circuit open
• CMP circuit short to GND
• CMP circuit short to PWR
• SIG RTN open (VR sensor)
• CMP GND open (Hall effect sensor)
• CMP misinstalled (Hall effect sensor)
• Damaged CMP sensor shielding
• Damaged CMP sensor
• Damaged PCM

Harness routing, harness alterations, improper shielding, or electrical interference from other improperly functioning systems may have intermittent impact on the CMP signal.

Wolfstang79:

Welcome to the forum and congrats on the new-to-you fine ride.

As the erstwhile "wmburns" mentioned, it is most likely a sickly alternator. If you search here for that code, you'll find quite a few Mustang owners have been fooled and missed the faulty alternator.

Whatever the reason for the code popping up, please post up an update. We don't like cliffhangers.

Chris

pretty much repeating what wmburns had said about checking the wiring. Give the wires that go into the connector at the sensor a good tug I have seen them break off inside the plug.

I think the issue with spark plug wire interference would be from spark plug wires getting to close to the sensor wiring and inducing false signals. Since your 02 has coil-on-plugs (COP) and doesn't have high voltage plug wires draped all over the front of the motor, plug wire interference seems pretty unlikely.