P0340 on 2008-2013 BMW M3: Camshaft Sensor 'A' (Bank 1) Causes and Fixes

What's Unique About the 2008-2013 BMW M3

The high-revving S65 V8 engine has four camshaft position sensors—one intake and one exhaust for each cylinder bank. Code P0340 specifically identifies the intake sensor on Bank 1 (the passenger side in LHD vehicles). An interesting issue noted by specialists is that these sensors can be sensitive to oil quality and moisture content; cars that are stored for long periods or have extended oil change intervals may trigger this fault even if the sensor is mechanically sound. Additionally, because the sensors are located under the valve covers, faults can sometimes be accidentally introduced during services like valve cover gasket replacements, such as a disconnected plug or a loose mounting bolt.

Symptoms You May Notice

• Check Engine Light is on
• Difficulty starting the engine (long crank time)
• Engine cranks but does not start
• Rough idle or unstable engine speed
• Engine stalling, especially at low speeds or randomly at traffic lights
• Noticeable loss of power and acceleration
• Vehicle may enter 'limp mode' with reduced performance
• Reduced fuel economy

Most Likely Causes

1. Failed Bank 1 Intake Camshaft Position Sensor 🔴 High Probability → Shop Engine Camshaft Position Sensor Heat cycles and oil exposure in the cylinder head can cause the sensor's internal electronics to fail over time. It is a common failure part on many BMW engines and is considered a maintenance item on the S65.
   How to confirm: Swap the Bank 1 intake sensor with the Bank 2 intake sensor. Clear the codes and run the engine. If the fault code changes to P0345 (Camshaft Position Sensor 'A' Circuit - Bank 2), the sensor is confirmed bad. All four sensors on the S65 engine share the same part number.
   Typical fix: Replace the faulty camshaft position sensor. It is highly recommended to use a Genuine BMW or OEM-supplier (e.g., VDO) part. Aftermarket sensors are known to be unreliable.
   Est. part cost: $150-$220
2. Wiring or Connector Issue 🟡 Medium Probability The sensor connector can become disconnected or the wiring can become brittle and damaged from engine heat, especially during other maintenance like spark plug or valve cover gasket changes.
   How to confirm: Visually inspect the sensor's electrical connector to ensure it is fully seated and the locking tab is engaged. Check the wiring harness leading to the sensor for any signs of damage, melting, or corrosion. A YouTube video by 'E92M3London' documents a case where a main dealer service left the sensor unplugged, causing this exact code. 🎬 Watch: E92M3London's diagnosis of a disconnected sensor plug.
   Typical fix: Securely reconnect the plug. If the connector or wiring is damaged, it will need to be repaired or replaced.
   Est. part cost: $0-$50
3. Poor Oil Quality or Contamination ⚪ Low Probability As noted by parts suppliers, the sensors on the S65 can be sensitive to moisture in the oil, which can occur in vehicles that are not driven regularly. Debris from other services, like an oil filter housing gasket replacement, can also clog VANOS passages and affect sensor readings.
   How to confirm: This is difficult to confirm directly but should be considered if the car has been in storage or is overdue for an oil change. Check the oil condition and service history.
   Typical fix: Perform an oil and filter change. Clear the codes and see if the fault returns. If the issue occurred after other engine work, consider inspecting the VANOS solenoids for debris.
   Est. part cost: $80-$150

Rare But Worth Checking

• Failing Engine Control Module (DME): → Shop Engine Control Module (ECM) This is very rare, but if the sensor and wiring have been tested and are known to be good, a fault within the DME's internal circuitry is a remote possibility. This is more likely if the old sensor failed with an internal short, potentially damaging the DME driver circuit.
• VANOS System or Timing Chain Issue: → Shop Engine Timing Chain A problem with the VANOS solenoids or a stretched timing chain could potentially cause camshaft position errors, but these issues would typically be accompanied by other, more specific fault codes (like 2A82, 2A87, or P0016).

Diagnosis Steps

1. Read the fault codes with a BMW-capable OBD-II scanner to confirm P0340 is present and check for any other related codes.
2. Remove the plastic engine cover and the Bank 1 (passenger side, cylinders 1-4) valve cover. This requires disconnecting the coolant reservoir and moving it aside for access.
3. Locate the intake camshaft position sensor. It is one of two sensors at the front of the cylinder head, held in by a single 5mm hex bolt.
4. Crucially, check if the electrical connector is fully plugged into the sensor. A loose connection is a simple but common cause, especially after recent service.
5. If connected, inspect the wiring for any visible damage (brittleness, melting, exposed wires).
6. To definitively test the sensor, swap the Bank 1 intake sensor with the Bank 2 (driver's side) intake sensor. They are the same part number and interchangeable.
7. Reinstall the valve covers with new gaskets, clear the fault codes, and start the engine. Let it run for a few minutes.
8. Re-scan for codes. If code P0345 (Bank 2) now appears, the sensor you moved is faulty and needs to be replaced.
9. If code P0340 returns, the problem lies in the wiring for Bank 1 or, rarely, the DME itself. Use a multimeter to test the wiring for continuity, shorts to ground, and proper reference voltage (typically 5V) from the DME.
10. If the sensor is confirmed bad, replace it with a new, high-quality part (Genuine BMW or VDO) and a new o-ring (Part No. 13627796699).

Parts You'll Likely Need

• Camshaft Position Sensor (OEM #13627837904) — This sensor is the most common cause of the P0340 code due to electronic failure over time. All four sensors on the S65 are identical.
  Trusted brands: Genuine BMW, VDO (OEM)
  OEM price range: $150-$220
  Aftermarket price range: $100-$150
• Valve Cover Gasket Set (Bank 1) (OEM #11127838271) — The valve cover must be removed to access the sensor. It is mandatory to replace the gasket at the same time to prevent oil leaks, as they are single-use and prone to hardening from heat. 🎬 Watch: Step-by-step S65 valve cover gasket replacement guide.
  Trusted brands: Genuine BMW, Elring, Victor Reinz
  OEM price range: $60-$90
  Aftermarket price range: $40-$60

Platform-Specific Known Issues

• A user on M3Post.com reported having the exact same issue (P0340) immediately after a valve cover gasket job. The cause was a loose bolt holding the sensor to the valve cover; tightening it resolved the code.
• A YouTube video from 'E92M3London' documented a P0340 fault that appeared after service at a BMW main dealer. Upon inspection, the sensor's electrical connector was found to be completely unplugged. Plugging it back in fixed the issue instantly.

Mechanic-Grade Diagnostic Values

• Camshaft Sensor Connector Voltage (KOEO) — expected: Pin 1 (Supply): ~5V DC. Pin 2 (Ground): < 0.1V DC (good continuity to ground). Pin 3 (Signal): ~5V DC.. Failure: No voltage on Pin 1 or 3 points to a wiring or DME issue. Voltage significantly different from 5V.
• Camshaft Sensor Signal Test (Sensor Plugged In) — expected: Using a multimeter, the signal wire (Pin 3) should toggle between ~5V and ~0V as a ferrous metal object is passed in front of the sensor tip.. Failure: Voltage does not change or does not drop close to 0V. This indicates a faulty sensor.
🎬 See this walkthrough on testing BMW camshaft sensor signals.
• Alternator AC Ripple Voltage — expected: < 100mV AC measured at the battery terminals with the engine running at ~1500 RPM.. Failure: AC voltage exceeding 100-200mV. This indicates a failing diode in the alternator, which can create electrical noise that disrupts the camshaft sensor's signal, causing a P0340 code even with a good sensor and wiring.

Hidden / Shadow Codes Worth Checking

• 0x271A: DME: Camshaft sensor, inlet, plausibility. This is the BMW-specific code logged in the DME that corresponds to the generic P0340. It indicates the signal from the Bank 1 intake cam sensor is illogical or missing when compared to the crankshaft sensor signal. (see via BMW-specific diagnostic software like ISTA, INPA, or high-end professional scan tools.)

Scan Tool Commands That Help

• ISTA (BMW Dealer Software): Perform VANOS system test — Use this function if a new sensor does not resolve P0340, or if it is accompanied by other VANOS-related codes (e.g., 27BB). The test actuates the solenoids and measures camshaft adjustment times, which can definitively identify a mechanical VANOS problem (like a sticking solenoid) versus an electrical sensor or wiring issue.
• ISTA (BMW Dealer Software): Delete adaptation values — This should be performed after replacing major VANOS components or performing timing work to reset the DME's learned adjustments for valve timing. While not strictly required for a simple sensor swap, it can be a useful step if driveability issues persist.

Wiring & Ground Locations

• Camshaft Sensor Connector (Bank 1 Intake) — At the front of the Bank 1 (passenger side) cylinder head, under the valve cover.. This is the direct connection point for the sensor. Pin 1 is +5V supply, Pin 2 is ground, and Pin 3 is the signal wire to the DME. All voltage and signal tests start here.
• Main Engine Ground Strap — Underneath the car, connecting the engine block to the chassis. On the E9x M3, it is typically located on the driver's side, near the engine mount and header-to-x-pipe connection.. This is the primary ground path for the entire engine. If this strap becomes corroded or breaks, which is a known issue, it can cause unstable sensor grounds, leading to erratic sensor readings and codes like P0340, along with no-start conditions.

Real Owner Repair Stories

• M3Post forum user experience (2009 BMW M3 E92) — Persistent P0340 code, occasional long crank, and rough idle, especially after the car warmed up.
  ❌ Tried (didn't work) Replaced the Bank 1 intake camshaft position sensor with a new Genuine BMW part., Swapped the new sensor with the Bank 2 sensor; fault remained on Bank 1 (P0340)., Visually inspected the wiring harness near the sensor connector for damage; none was found.
  ✅ What actually fixed it The owner inspected the main engine-to-chassis ground strap located under the driver's side of the car. The strap was found to be severely corroded and frayed. After replacing the ground strap with a new OEM part and cleaning the contact points on the chassis and engine block to bare metal, the P0340 code was cleared and did not return. The unstable ground path was causing voltage fluctuations in the sensor circuit that the DME interpreted as a sensor fault.

OEM Part Supersession History

• 13627837904 → 13627837904 — No supersession found. This part number appears to be consistent for the entire production run of the S65 engine.

Model Year Variations Within This Range

• 2008-2013: No significant variations related to the camshaft position sensor circuit, its causes, or fixes have been documented across the E9x M3 model years. Minor engine accessory changes in early production do not affect this system.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Rod Bearing Wear 🔴 High — Extremely well-documented issue. Considered a mandatory preventative maintenance item by many owners, often replaced between 60,000-80,000 miles. Failure can be catastrophic to the engine. (Ref: No official recall, but was the subject of a class-action lawsuit.)
• Throttle Body Actuator Failure 🔴 High — Very common failure, typically occurring between 50,000-80,000 miles. The engine has two actuators, and failure of one will put the car in limp mode. Often both are replaced at the same time.
• Valve Cover Gasket Leaks 🟠 Medium — Extremely common oil leak source. The gaskets harden over time due to engine heat and begin to leak oil onto the exhaust manifolds, causing a burning smell.
• Idle Control Valve Failure 🟠 Medium — A common cause of rough, erratic, or hunting idle when the engine is warm. Failure can also cause stalling.
• Main Bearing Failure 🔴 High — Less discussed than rod bearings but a known cause of catastrophic engine failure, particularly affecting the #1 main bearing due to stresses from the timing chain assembly.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used OEM sensor from a low-mileage wrecked vehicle can be a viable option if on a tight budget, as OEM electronics are generally robust. However, given the labor to access the sensor (valve cover removal), the cost savings may not be worth the risk of a shorter lifespan compared to a new part.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Ask for the VIN or mileage of the donor car.
• Inspect the electrical connector pins for any signs of corrosion or damage.
• Check the plastic housing for cracks or signs of extreme heat exposure.
• Ensure the o-ring is present or purchase a new one separately.

OEM-only on this vehicle (don't cheap out):

• Camshaft Position Sensor

Aftermarket brands forum-validated for this vehicle:

• VDO (This is the Original Equipment Manufacturer for BMW)

Brands owners have reported issues with on this vehicle:

• Unbranded 'white-box' sensors from online marketplaces (e.g., eBay, Amazon) are frequently reported on forums to be dead-on-arrival or fail within a few months.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0345 — This is the code for Camshaft Position Sensor 'A' Circuit - Bank 2. Because the S65 uses identical sensors on both banks, swapping a suspected bad sensor from Bank 1 to Bank 2 will cause the code to change from P0340 to P0345.

Frequently Asked Questions