What does it mean?
This is a generic powertrain diagnostic trouble code (DTC), meaning it covers all makes/models from 2003 onward. The code appears more common on Kia, Hyundai, Chevrolet, Toyota, and Ford vehicles, but any brand vehicle can be affected.
Specific troubleshooting steps vary by vehicle.
These vehicles may have a single in-block camshaft or a single overhead camshaft (SOHC) or dual (DOHC), but this code is strictly concerned with the incoming signal from the Bank 1 ‘B’ camshaft position sensor(s) being missing, typically during engine startup. It is an electrical circuit fault. Bank #2 is the engine bank that does not contain cylinder #1.
The PCM uses the camshaft position sensor to tell it when the crankshaft sensor signal is correct, when a given crankshaft position sensor signal is timed to cylinder #1 for timing, and it is also used for the timing/start of fuel injector fuel injection.
P0390 or P0391 codes may also be present alongside P0393. The only difference between these 3 codes is the duration of the issue and the type of electrical problem encountered by the sensor/circuit/engine controller. Troubleshooting steps may vary by manufacturer, camshaft position sensor type, and wire colors.
Symptoms
Symptoms of a P0393 engine code may include:
Check Engine Light illuminated
Engine misfiring or surging
Stalls, but may restart if the issue is intermittent
May run fine until restarted; will not restart
Potential Causes
Typically, causes for this code are:
Open in the ground circuit for the Bank 2 ‘B’ camshaft position sensor
Open in the signal circuit between the ‘B’ camshaft position sensor and the PCM
Short to 5 volts in the camshaft position sensor signal circuit
Faulty camshaft position sensor – internal short to voltage
Diagnostic and Repair Procedures
A good starting point is always checking for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogram to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.
Next, locate the camshaft and crankshaft position sensors on your specific vehicle. Since they share common power and ground circuits, and this code focuses on the camshaft position sensor’s power and ground circuits, it makes sense to check them for any damage to either. Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Disconnect the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear corroded, burnt, or perhaps greenish compared to the normal metal color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If not available, find 91% isopropyl alcohol and a soft plastic-bristled brush to clean them. Then, let them air dry, get some dielectric silicone compound (same as used for bulb sockets and spark plug wires), and apply a small amount where the terminals make contact.
If you have a scan tool, clear the diagnostic codes from memory and see if this code returns. If not, the connections were likely your problem.
If the code returns, we’ll need to test the sensor and its associated circuits. There are generally 2 types of camshaft position sensors: Hall effect or magnetic pickup sensor. You can usually tell which you have based on the number of wires from the sensor. If there are 3 wires from the sensor, it’s a Hall effect sensor. If it has 2 wires, it will be a magnetic pickup type sensor.
This code will only set if the sensor is a Hall effect sensor. Disconnect the harness going to the camshaft position sensor. With a digital volt-ohm meter (DVOM), test the 5V power circuit going to the sensor to ensure it has power (red lead to the 5V/12V power circuit, black lead to a good ground). Check with a wiring diagram or diagnostic chart whether this sensor is supplied with 5 volts or 12 volts. If there are 12 volts at the sensor when there should be 5 volts, repair the wiring from the PCM to the sensor for a short to 12 volts, or possibly a faulty PCM.
If that’s okay, with a DVOM, check that the camshaft position sensor signal circuit has 5V (red lead to the sensor signal circuit, black lead to a good ground). If there is no 5 volts at the sensor, or if you see 12 volts at the sensor, repair the wiring from the PCM to the sensor, or again a faulty PCM.
If that checks out, verify you have a good ground at each sensor. Connect a test light to the positive 12V battery terminal (red clip) and touch the other end of the test light to the ground circuit going to the camshaft sensor circuit ground. If the test light does not illuminate, that would indicate the circuit problem. If it lights up, wiggle the wire harness going to each sensor to see if the test light flickers, indicating an intermittent connection.
Related camshaft fault codes: P0340, P0341, P0342, P0343, P0345, P0346, P0347, P0348, P0349, P0365, P0366, P0367, P0368, P0369, P0390, P0391, P0392, P0394.