P0340: Camshaft Position Sensor Circuit Malfunction

What is P0340?

Error code P0340 is an OBD-II diagnostic trouble code defined as “Camshaft Position Sensor Circuit Malfunction” or “Camshaft Position Sensor A Circuit Malfunction.” 

It refers to the entire circuit attached to the camshaft position sensor (CMP sensor or cam sensor). So, the problem isn’t necessarily related to a bad camshaft position sensor alone. 

Besides a defective camshaft position sensor, it could be parts like the electric wiring in and around your camshaft position sensor. The Engine Control Module (ECM or ECU) and Powertrain Control Module (PCM) could be at fault too. 

Therefore, simply replacing the camshaft position sensor is often not enough to fix the P0340 fault code. You need to address the issue properly to deactivate the check engine light (CEL).  

Curious about the camshaft position sensor’s function?
Your CMP sensor calculates your engine’s camshaft rotation speed and tracks the shaft’s position. It also signals to the PCM or ECM to set the fuel injector timing and, in conjunction with the crankshaft position sensor (crank sensor), ignition timing.

Any signal disruption throws off the engine timing, triggering the check engine light, P0340 trouble code, and other engine codes.

Common Symptoms

You may experience one or more of these symptoms with an active P0340 fault code:

• Illuminated check engine light
• Engine cranking without starting
• Engine stalling
• Engine misfires or rough running (sometimes accompanied by misfire codes such as P0300, P0301, and P0316.)
• Loss of power while driving
• Transmission shifting issues
• Increased fuel consumption
• No spark plug activation when you turn the ignition switch

Can I Still Drive?

Immediately discontinue driving if you have an active P0340 code or an illuminated check engine light.

DTC P0340 is a severe error code, and it could be dangerous to continue driving with this fault code. You don’t want to risk your engine stalling while on the highway.

Furthermore, you risk damaging your vehicle’s ignition system if you continue to drive with the P0340 trouble code active — leading to an expensive repair job.

P0340 Causes

Here are the most common causes of DTC P0340:

• A faulty camshaft position sensor won’t accurately signal to your PCM when to inject fuel.

• An open circuit within the circuit wiring of the camshaft position sensor can disrupt voltage flow and compromise communication between your engine computer and the camshaft sensor.

• A defective connector to your camshaft position sensor circuit can interfere with the signal between the sensor and your ECU.

• A faulty crankshaft sensor could affect the ignition timing and spark plug activation.

• A faulty crankshaft position sensor reluctor wheel can prevent your ECM or PCM from accurately tracking your crankshaft’s position. A magnetic sensor detects the teeth of the reluctor wheel while it rotates and relays this information to the ECM.

• A defective PCM or ECM won’t accurately pick up the signals from your cam sensor or crank sensor.

• Lastly, incorrect installation or incompatible aftermarket sensors may also be the culprit. Additionally, aftermarket sensors may wear out faster, and it’s unlikely your warranty will cover them.

Diagnosis

Diagnosing a P0340 code isn’t a DIY task due to its complexity. So, it’s best to get a mechanic to attend to your automotive vehicle. 

Here’s how your mechanic will diagnose error code P0340 to find the root cause of the bad sensor circuit:

1. Use an OBD 2 scan tool to retrieve all other trouble codes stored by your PCM or ECM (often misfire codes). 

2. Check the continuity of the cam position sensor circuitry by inspecting the cam sensor wiring and wiring harness (they might use a wiring diagram as a guide). They’ll check to see if there’s been a short or open circuit  and if any frayed CMP sensor wiring is interfering with the voltage.

3. Check each camshaft position sensor connector (harness connector) to see if they’re broken or corroded.

4. Use a multimeter to test your camshaft sensor volt reading.

5. Look at your crankshaft position sensor and crank sensor circuit wiring to see if there’s any damage or need for a sensor replacement.    

6. Inspect your timing belt and its tensioner for any faults.

7. Finally, inspect your Powertrain Control Module or Engine Control Module to see if they’re defective or damaged.

Once diagnosed, the mechanic will begin with the possible solutions for the defective camshaft position sensor or other bad sensor components.

Possible Repairs for P0340 & Costs

Since there are multiple possible causes of the check engine light code P0340, your mechanic will need to complete the entire diagnostic process before performing any possible solutions. 

You don’t want to pay for a new Powertrain Control Module or Engine Control Module when your CMP sensor wiring is causing a short circuit problem.

Here’s how a mechanic will fix the different causes of engine light code P0340:

• Other error codes: Fix any other active error codes in order of seriousness.

• Camshaft position sensor: Replace your cam position sensor wiring and each camshaft position sensor connector if damaged, corroded, or frayed. Then, they’ll replace your faulty camshaft position sensor if required.

• Crankshaft position sensor: Perform the same repairs on your crank sensor. So, your mechanic will replace your crankshaft sensor wiring and each harness connector if damaged. They’ll also install a new crankshaft position sensor if it’s faulty.

• Timing belt: If your timing belt slips, putting it back in position is challenging. So, they’ll likely replace it with a new one. The timing belt should be replaced every 60,000-100,000 miles.

• Timing belt tensioner: Replace it if required. The tensioner maintains the appropriate tension in the timing belt.

• Timing cover:  Replace it if necessary. The timing cover protects the timing components of the engine from debris.

• PCM and ECM: If none of the above repairs resolve the issue, try fixing your PCM and ECM. They’ll install new ones if damaged beyond repair.

Let’s look at how much these different car repair jobs will set you back. 

Here are some P0340 code repair estimates (including labor charges):

• Camshaft sensor replacement: $100-$300
• Crankshaft position sensor replacement: $120-$300
• Timing belt replacement: $400-$1000
• ECM replacement: $800-$1500
• PCM replacement: $800-$1500