P0024 on 2007-2012 Mercedes-Benz GL-Class: M273 Exhaust Cam Timing Causes and Fixes

What's Unique About the 2007-2012 Mercedes-Benz GL-Class

The M273 V8, like its M272 V6 sibling, is well-known for issues with its camshaft adjuster magnets (solenoids). These components are a frequent failure point, leading to timing-related codes like P0024. They not only fail electronically but are notorious for leaking oil through their internal seals and into the engine wiring harness. This oil can wick all the way to the main engine computer (ECU), causing thousands of dollars in damage. While early M273 engines (before serial no. 2739..30 088611) also had a serious issue with a soft timing chain idler sprocket, a solitary P0024 code usually points to the much simpler and cheaper magnet failure rather than the catastrophic internal engine problem.

Symptoms You May Notice

• Check Engine Light is on
• Rough or unstable idle, especially on cold start
• Engine stalling
• Reduced engine power and hesitation during acceleration
• Decreased fuel economy
• Rattling or knocking noises from the front of the engine upon startup

Most Likely Causes

1. Faulty Camshaft Adjuster Magnet (Solenoid) 🔴 High Probability These magnets are a very common failure point on M272 and M273 engines. They can get stuck, fail electronically, or develop internal seals that leak oil into the wiring harness.
   How to confirm: Unplug the electrical connector for the Bank 2 (driver's side) exhaust camshaft magnet. Inspect for engine oil inside the connector; oil presence confirms a bad magnet. A common diagnostic test is to swap the exhaust magnet with the intake magnet on the same bank. If the code changes from P0024 to P0021, the magnet is faulty.
   Typical fix: Replace the faulty camshaft adjuster magnet. It is highly recommended to replace all four magnets (intake and exhaust on both banks) at the same time as a preventative measure. Also, install a short adapter pigtail harness (part no. 2711500156) to prevent future oil contamination of the main harness. 🎬 See why ignoring these leaking magnets can be so costly.
   Est. part cost: $30-$80 per magnet
2. Low or Dirty Engine Oil 🟡 Medium Probability The VVT system is operated by oil pressure. Incorrect oil viscosity, low oil level, or oil that is dirty and sludged can restrict the small passages in the system, preventing the camshaft adjusters from working correctly.
   How to confirm: Check the engine oil level and condition. Review service records to ensure oil changes have been performed with the correct Mercedes-Benz approved synthetic oil (MB 229.5 specification) and a fleece filter.
   Typical fix: Perform an engine oil and filter change using high-quality, manufacturer-specified oil and a fleece filter.
   Est. part cost: $70-$150 for oil and filter
3. Faulty Camshaft Position Sensor ⚪ Low Probability
   How to confirm: If replacing the adjuster magnet doesn't solve the issue, the sensor that reads the camshaft's position may be faulty. This can be tested by swapping it with the sensor from the intake cam or the other bank to see if the code follows the sensor. The sensor is located near the magnet.
   Typical fix: Replace the Bank 2 exhaust camshaft position sensor.
   Est. part cost: $40-$100

Rare But Worth Checking

• Worn Timing Chain Idler Sprocket: This was a major issue on early M273 engines (before engine serial number 2739..30 088611). 🎬 Watch: How to check for catastrophic sprocket wear before it's too late. A worn sprocket causes timing chain slack, leading to correlation codes. This is a catastrophic, engine-out repair. This is usually indicated by codes P0016/P0017 appearing alongside P0024, not just P0024 alone.
• Failed Camshaft Adjuster (Phaser): The mechanical gear assembly (phaser) that the magnet controls can fail internally, often causing a loud rattling noise at startup that persists. This is a much more involved and expensive repair than replacing the magnet. Internal wear on the locking pin or plate can cause failure.

Diagnosis Steps

1. Check the engine oil level and condition. Top off or perform an oil change with MB 229.5 specification oil if necessary.
2. Use an OBD-II scanner (preferably one with Mercedes-specific capabilities like iCarsoft or STAR Diagnosis) to check for any other codes. The presence of P0016, P0017, 1200, or 1208 indicates a potentially more severe issue.
3. Locate the camshaft adjuster magnets on the front of the cylinder heads. Bank 2 is the driver's side. The exhaust magnet is the outer one, typically lower than the intake magnet.
4. Unplug the electrical connector from the Bank 2 exhaust magnet. Carefully inspect the connector and the magnet's pins for any sign of engine oil. If oil is present, the magnet has failed and must be replaced.
5. If no oil is found, perform a swap test. Swap the Bank 2 exhaust magnet (P0024) with the Bank 1 exhaust magnet (passenger side). Clear the codes and run the engine.
6. If the code changes to P0014 (Bank 1 Exhaust), the magnet you moved is confirmed to be faulty and needs replacement.
7. If the code P0024 returns, the problem lies elsewhere. Consider testing or swapping the camshaft position sensor next.
8. The magnets are held by three E8 external Torx bolts. An E8 Torx spanner or a small 1/4" drive wrench may be needed for the less accessible bolts, especially on the driver's side. An 8mm 12-point wrench can also be used in tight spaces.
🎬 Watch: Step-by-step guide to removing the magnets and sensors.

Parts You'll Likely Need

• Camshaft Adjuster Magnet (Solenoid) (OEM #A2720510177) — This is the most common cause of P0024 on the M273 engine due to high failure rates from electronic malfunction or internal oil leaks. This is an updated part number; the original was 2720510077.
  Trusted brands: Genuine Mercedes-Benz, Bosch, Pierburg
  OEM price range: $50-$80
  Aftermarket price range: $25-$50
• Camshaft Magnet Harness Extension Pigtail (OEM #2711500156) — This is a highly recommended preventative part. It acts as a sacrificial harness to catch oil leaking from a failing magnet, preventing it from wicking into the main engine harness and destroying the ECU, which is a very expensive repair.
  Trusted brands: Genuine Mercedes-Benz
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Camshaft Position Sensor (OEM #A2729050043) — A less common cause, this sensor can fail and send incorrect position data to the ECU. It's often replaced as a precaution when addressing cam timing codes if the magnet swap doesn't resolve the issue.
  Trusted brands: Genuine Mercedes-Benz, Bosch, Continental/VDO
  OEM price range: $50-$100
  Aftermarket price range: $30-$60

Related Codes That Often Appear With This One

• P0021 — Intake camshaft timing over-advanced on the same bank (Bank 2). Can appear if multiple magnets are failing or if a diagnostic swap was performed.
• P0016 / P0017 — Crankshaft/Camshaft position correlation errors. If these codes are present with P0024, it strongly suggests a more serious mechanical timing problem, such as a stretched timing chain or a worn idler sprocket, and requires immediate professional diagnosis.
• 1200 / 1208 — These are Mercedes-specific fault codes that often accompany P0016/P0017 and point toward the catastrophic idler gear/balance shaft issue on M272/M273 engines. 1208 corresponds to Bank 1 (passenger side) and 1200 to Bank 2 (driver's side).

Technical Service Bulletins (TSBs) & Recalls

• S-B-03.30/08i - This service bulletin addresses worn idler gears on M273 engines (and balance shafts on M272s), which can cause timing correlation fault codes. It also details procedures for diagnosing leaking or faulty camshaft adjuster solenoids and provides updated engine serial number ranges for the affected components.

Platform-Specific Known Issues

• Oil wicking from the camshaft adjuster magnets into the main engine wiring harness is a well-documented problem on M272 and M273 engines. Installing inexpensive pigtail harnesses is a critical preventative measure to avoid ECU damage that can cost upwards of $7,000 to repair.
• Early production M273 engines (before engine serial number 2739..30 088611) are susceptible to premature wear of the timing chain idler gear sprocket, a very expensive repair requiring engine removal. This is typically indicated by codes P0016/P0017 and/or Mercedes-specific codes 1200/1208.

Mechanic-Grade Diagnostic Values

• Camshaft Adjuster Magnet (Solenoid) Internal Resistance — expected: 10-18 Ohms. Failure: An open circuit (infinite resistance), a short (zero resistance), or a reading far outside the expected range indicates a failed solenoid.
• Camshaft Position Sensor Voltage (Live Data) — expected: Typically 0.5V - 4.5V. Failure: A consistently high or low voltage, or a signal that does not change with engine RPM, can indicate a faulty sensor.

Hidden / Shadow Codes Worth Checking

• 1200: Constant adjustment of exhaust camshaft of left cylinder bank in direction 'Retarded' (P0024 equivalent). Often indicates a mechanical timing issue (stretched chain, worn idler gear) rather than just a magnet failure, especially if paired with 1208. (see via Mercedes-specific scan tool like XENTRY/DAS.)
• 1208: Constant adjustment of intake camshaft of right cylinder bank in direction 'Retarded' (P0016 equivalent). While not directly for P0024, its presence alongside 1200 or other timing codes strongly points to the major idler gear/balance shaft problem. (see via Mercedes-specific scan tool like XENTRY/DAS.)

Scan Tool Commands That Help

• Mercedes XENTRY/DAS or advanced bidirectional scanner: VVT Solenoid Actuator Test — This command allows you to manually activate the Bank 2 exhaust solenoid while the engine is running. If the solenoid is functioning correctly, activating it should cause the engine to hesitate or stall. If there is no change in engine operation, it confirms a problem with the solenoid, its wiring, or the oil passages.

Wiring & Ground Locations

• Main Engine Ground Strap — Typically a braided copper cable running from the transmission bell housing (driver's side) to the chassis, under and to the rear of the steering box.. While not a direct cause, a poor engine ground can create a host of electrical gremlins and unstable sensor readings. Ensuring this primary ground is clean and secure is a crucial step in any electrical diagnosis to prevent misdiagnosis of components like sensors and solenoids.
• Engine Bay Ground Points (W164) — On the W164 chassis, there are main grounding points on both the driver and passenger side inner fenders, just forward of the firewall. They are identifiable by a stud with multiple brown wires attached.. These points ground numerous engine bay components. Corrosion or looseness here can affect the ECU and its ability to correctly read sensor data and control actuators like the camshaft magnets. Verifying these are clean and tight is good practice.

Real Owner Repair Stories

• MBWorld.org user 'go000ob' (2007 C230 (M272 engine, same magnet design as M273)) — Check Engine Light with camshaft-related codes.
  ❌ Tried (didn't work) The user had previously replaced all 4 camshaft magnets 2 years prior to solve the issue.
  ✅ What actually fixed it After the codes returned two years later, replacing all four camshaft magnets again with new OEM parts resolved the Check Engine Light. The user concluded that the magnets may need to be replaced every few years as a maintenance item.

OEM Part Supersession History

• 2720510077 → A2720510177 — The original part was prone to internal oil leaks. The updated part has improved seals to mitigate this common failure mode.
• N/A → 2711500156 (Pigtail Harness) — This part was created by Mercedes-Benz as a solution to prevent oil from failed magnets (A2720510177) from wicking into the main engine harness. It's a preventative addition, not a direct replacement.

Model Year Variations Within This Range

• 2007-2008 (Early Production): Engines built before serial number 2739..30 088611 are susceptible to the worn timing chain idler sprocket. A solitary P0024 code is still likely the magnet, but if accompanied by P0016/P0017 or Mercedes codes 1200/1208, this major internal engine flaw is the probable cause.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• AIRMATIC Air Suspension Failure 🔴 High — Very common, typically after 80,000-150,000 kilometers. Failures include leaking air springs (bags), worn compressors, and faulty valve blocks.
• Intake Manifold Runner Control Failure 🟠 Medium — Common failure where the plastic actuating levers for the internal swirl flaps break. This causes poor idle, loss of power, and can set codes like P2004, P2005, or P2006.
• Power Tailgate Latch/Motor Failure 🟠 Medium — The soft-close motor or the latch mechanism in the power liftgate frequently fails, preventing the tailgate from latching securely.
• Timing Chain Idler Sprocket Wear (Early Engines) 🔴 High — Affects M273 engines manufactured before serial number 2739..30 088611. A soft metal idler gear wears prematurely, causing catastrophic engine damage. This is a very expensive, engine-out repair. (Ref: S-B-03.30/08i)
• Transmission Conductor Plate/Valve Body Failure 🔴 High — The 7G-Tronic (722.9) transmission's internal electronic conductor plate is prone to failure, causing harsh shifting, getting stuck in gear, or loss of drive. This often occurs around 100,000-150,000 km.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, buying a used camshaft adjuster magnet is NOT recommended. The failure rate of this part is very high due to both electronic malfunction and internal oil seal degradation. A used part has an unknown history and is likely to fail soon, if it hasn't already. The cost of a new, quality aftermarket part is low enough that the risk of a used part is not worthwhile.

What to inspect on the donor part:

• Not applicable, as used parts are not recommended.

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

• While not strictly OEM-only, it is critical to use a reputable brand for the Camshaft Adjuster Magnet. Cheap, unbranded parts from online marketplaces are known to have very high failure rates.

Aftermarket brands forum-validated for this vehicle:

• Pierburg (often the original OEM supplier)
• Bosch

Brands owners have reported issues with on this vehicle:

• Unbranded, no-name parts from marketplaces like eBay and Amazon should be avoided. While they may be cheap, they often fail quickly, leading to the code returning.

Real Owner Stories

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

Related OBD-II Codes

• P0021 — This is the intake camshaft equivalent for Bank 2; the code may switch to this during a diagnostic swap test if the magnet is faulty.
• P0014 — The Bank 1 exhaust equivalent; if P0024 moves to this code after swapping magnets across banks, it confirms the magnet is the issue.
• P0016 — A timing correlation code that, when appearing with P0024, often indicates more severe internal wear of the idler gear sprocket.
• P0017 — A timing correlation code frequently seen alongside P0016 on early M273 engines with worn timing components.
• 1200 — A Mercedes-specific diagnostic code that indicates serious timing issues related to the idler gear sprocket on M273 engines.
• 1208 — A Mercedes-specific diagnostic code often paired with 1200, signaling premature wear of the timing chain idler gear.

Frequently Asked Questions