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Mercedes-Benz · Known Issues

2012 Mercedes-Benz B-Class Problems: 6 Known Issues

2012 model year · 680+ owner reports · Updated October 2026

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Issue summary

According to Au7o's analysis of 680+ owner reports, the 2012 Mercedes-Benz B-Class has 6 documented known issues, with 2 rated critical. The most serious are Timing chain rattle and stretch on the 1.6-litre M270 (owner reports) and Driver airbag may deploy without a crash — recall 2017-490. The most commonly reported issue is Hesitant take-off and jerky low-speed shifts from the 7G-DCT (owner reports) with 680 owner reports. DIY maintenance guides at au7o.io.

In This Article

  • B-Class Engine1
  • B-Class Safety/Recalls1
  • B-Class Transmission1
  • B-Class Brakes1
  • B-Class Emissions1
  • B-Class Cooling1
  • FAQ
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In This Article

  • Engine1
  • Safety/Recalls1
  • Transmission1
  • Brakes1

All 6 Known Issues

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On the 2012-2018 Mercedes-Benz B-Class M270 DE16 1.6L turbo, owners of W246 B-Class cars with the 1.6-litre M270 petrol engine report a rattle at start-up and stretched timing chains. A 2011 B 180 was diagnosed by a Mercedes workshop with a stretched chain at 75,000 km, 2012 1.6-litre cars needed a new chain and sprockets (one also a camshaft adjuster and cylinder head), and a pre-facelift B 180's chain apparently jumped, damaging the engine. Applies to: Second-generation (W246) B-Class with the 1.6-litre M270 petrol engine (M 270 DE 16: B 180 and B 200), model years 2012-2018; not sold in Canada. One further report concerns a 2.0-litre B 200 Natural Gas Drive whose cold-start rattle returned after a tensioner replacement; no report was found for the 2.0-litre B 220 or B 250, and a forum regular says none has been posted. Not the diesel or electric models. Mileage when it happened, as stated in the linked owner reports: 26,000 km (about 16,200 miles), 75,000 km (about 46,600 miles) on a 2011 and 80,000 km (about 49,700 miles) on a 2012.

Common Symptoms

  • Engine warning light comes on and returns the day after clearing
  • Rattling or clacking from the engine just after a cold start
  • Cold-start rattle persists despite several workshop repair attempts

How to Fix

Check the oil level and that the oil meets the Mercedes specification in your owner's manual, then have a Mercedes technician listen to a cold start and check camshaft timing with diagnostic equipment. Owners report tensioner replacement as the first repair and full chain replacement where the chain has stretched; have the cause confirmed before ordering parts.

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On the 2012-2018 Mercedes-Benz B-Class, on certain vehicles, electrostatic discharge combined with a broken clock spring and insufficient grounding of the steering components could inadvertently deploy the driver's frontal airbag. An unintended deployment could startle the driver and cause a crash, and could cause minor injuries. Applies to: Certain 2012-2018 model-year B-Class sold in Canada, as listed in Transport Canada recall 2017-490 (also C, E and GLK). The record notes that a broken clock spring shows a driver airbag warning message and a red airbag warning lamp. Only a Mercedes-Benz dealer can confirm whether a specific VIN is included.

How to Fix

Have a Mercedes-Benz dealer check your VIN for this recall. The correction in the recall record: dealers will add sufficient grounding to the steering components. Airbag work is dealer-only.

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680 owners

On the 2012-2019 Mercedes-Benz B-Class, owners of W246 B-Class cars with the 7G-DCT dual-clutch automatic describe a pause of about a second before the clutch bites when pulling away, and jerking or harsh shifts at low speed. One owner of a high-mileage 2014 B 220 CDI reports judder that a transmission reset did not cure; the cause was not diagnosed in the thread. Applies to: Second-generation (W246) B-Class with the 7G-DCT automatic: model years 2012-2018 in Europe and 2013-2019 in Canada (B 250), with the M270 petrol (1.6 and 2.0 litre, including the B 200 Natural Gas Drive), OM651 diesel or OM607 1.5-litre diesel. The owner reports linked here are from a B 200, a B 200 CDI and a 2014 B 220 CDI. Not the B250e electric (W242), which has a single-speed drive unit, and not manual-gearbox cars. Mileage when it happened, as stated in the linked owner reports: 3,200 km (about 2,000 miles), 110,000 km (about 68,400 miles) on a 2016 and 230,000 km (about 142,900 miles) on a 2014.

Common Symptoms

  • Car hesitates about a second before pulling away from a stop
  • Pressing the throttle harder does not speed up the take-off
  • Jerking in normal driving and sometimes when pulling away
  • Occasional rough shifts, mostly between first and second gear
  • Car sometimes lurches forward when manoeuvring or parking

How to Fix

Owners suggest keeping to the Mercedes transmission-oil change interval and having the transmission adaptation values reset; one owner reports a reset made no difference, and another notes a reset alone helps only briefly. Have a Mercedes technician read the transmission control unit, test-drive with diagnostic equipment and check for software updates for your VIN before any clutch work is quoted.

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Based on 680 owner reports

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On the 2012-2019 Mercedes-Benz B-Class, w246 owners report a parking-brake malfunction warning, and in one case the electric parking brake worked on one side only. One owner found water in the left rear actuator motor and replaced both actuators, but the warning stayed until the parking-brake control module connectors inside the right rear of the car were unplugged and reseated. Applies to: Second-generation (W246) B-Class with the electric parking brake: model years 2012-2018 in Europe and 2013-2019 in Canada (B 250). The owner reports linked here include a 2012 car. Owners report the rear actuator motors, the wiring and the control module as the parts involved; the cause on a given car must be diagnosed.

Common Symptoms

  • "Parking Brake - See Owner's Manual" warning message on the dash
  • Electric parking brake stops working
  • Yellow and red parking-brake lights come on with a malfunction warning
  • Parking brake applies on one side only
  • Warning first clears after a restart, then stays on

How to Fix

If the parking brake warning appears, park on level ground with the transmission in P and do not rely on the parking brake alone. Have a Mercedes technician read the parking-brake control module fault codes and check the actuator motors, wiring and the control-module connectors before replacing parts. Brake work is technician-only.

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On the 2012-2018 Mercedes-Benz B-Class OM651 DE18 LA / DE22 LA diesel, owners of W246 OM651 diesel B-Class cars report the engine warning light with a particulate-filter fault. On a 2013 B 200 CDI the fault "particulate filter overloaded" returned after a sustained drive at higher engine speed; on a 2014 B 220 CDI the workshop first found a faulty differential-pressure sensor and then replaced the particulate filter. Applies to: Only diesel W246 B-Class models with the OM651 engine (B 180 CDI 1.8, B 200 CDI, B 220 CDI), model years 2012-2018, mainly cars used for short trips. Not the B 160 CDI or B 180 CDI with the Renault-sourced 1.5-litre OM607, and not petrol, natural-gas or electric models; the Canadian B 250 is petrol only. Mileage when it happened, as stated in the linked owner reports: 20,000 km (about 12,400 miles) and 123,000 km (about 76,400 miles) on a 2013.

Common Symptoms

  • Engine warning light comes on with a particulate-filter-overloaded fault
  • Warning light returns right after a high-rpm cleaning drive
  • Engine warning light keeps coming back after the fault is cleared

How to Fix

Have a Mercedes technician read the particulate-filter data (soot load, differential pressure) before anything is replaced; owners report a workshop-triggered regeneration drive as the first step, and caution that repeatedly clearing the fault without a regeneration lets the filter block completely and that a faulty differential-pressure sensor can also be the cause. Owners recall the owner's manual guidance that the diesel needs a longer drive regularly to burn the filter clean.

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On the 2012-2019 Mercedes-Benz B-Class, owners of W246 B-Class cars with the M270 petrol engine report coolant warning messages, an engine warning light with the temperature stuck around 70-80 C, or the gauge swinging, with dealers replacing an electronically controlled thermostat that stuck open. Some gauge movement is normal on this engine, and owners report a dealer engine-software update that steadied it where no hardware fault was stored. A thermostat replacement did not always cure it: other causes found were a crack elsewhere in the cooling system and a stuck valve in the water pump. Applies to: Second-generation (W246) B-Class with the M270 petrol engine (B 180, B 200, B 220 4MATIC, B 250): model years 2012-2018 in Europe and 2013-2019 in Canada (B 250). The owner reports linked here are from a B 220 4MATIC, a 2012 B 200 and other W246 petrol cars. Not the diesel or electric models. Mileage when it happened, as stated in the linked owner reports: 65,000 km (about 40,400 miles) on a 2013, 74,000 km (about 46,000 miles) on a 2012, 142,000 km (about 88,200 miles) on a 2012 and 176,000 km (about 109,400 miles) on a 2012.

Common Symptoms

  • Coolant temperature gauge swings up and down while driving
  • Engine warning light comes on
  • Engine temperature stays at 70-80 C and will not rise
  • Red "check coolant" message appears on the dash
  • Gauge climbs to 120 C with a "switch engine off" coolant warning

How to Fix

If the coolant temperature runs high or a coolant warning appears, stop and let the engine cool; never open the cooling system when hot. Have a Mercedes technician read the fault memory, pressure-test the cooling system and check the thermostat, temperature sensor and water pump. Owners report a software update where no hardware fault is stored, a thermostat replacement when it is stuck open, and a sensor, a cracked part or the water-pump valve in other cases, so confirm the cause first.

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Frequently Asked Questions

What are the most common Mercedes-Benz B-Class problems?

According to Au7o's analysis of 680+ owner reports, the 2012 Mercedes-Benz B-Class has 6 documented issues. The most frequently reported are: Timing chain rattle and stretch on the 1.6-litre M270 (owner reports), Driver airbag may deploy without a crash — recall 2017-490, Hesitant take-off and jerky low-speed shifts from the 7G-DCT (owner reports). Of these, 2 are rated critical and should be addressed promptly.

Is the Mercedes-Benz B-Class reliable?

The 2012 Mercedes-Benz B-Class has 6 known issues documented across 680+ owner reports. 2 issues are rated critical: Timing chain rattle and stretch on the 1.6-litre M270 (owner reports) and Driver airbag may deploy without a crash — recall 2017-490. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

What is the 2012-2018 Mercedes-Benz B-Class Timing chain rattle and stretch on the 1.6-litre M270 (owner reports)?

Owners of W246 B-Class cars with the 1.6-litre M270 petrol engine report a rattle at start-up and stretched timing chains. A 2011 B 180 was diagnosed by a Mercedes workshop with a stretched chain at 75,000 km, 2012 1.6-litre cars needed a new chain and sprockets (one also a camsh… Severity: high.

What is the 2012-2018 Mercedes-Benz B-Class Driver airbag may deploy without a crash — recall 2017-490?

On certain vehicles, electrostatic discharge combined with a broken clock spring and insufficient grounding of the steering components could inadvertently deploy the driver's frontal airbag. An unintended deployment could startle the driver and cause a crash, and could cause mino… Severity: high.

What is the 2012-2019 Mercedes-Benz B-Class Hesitant take-off and jerky low-speed shifts from the 7G-DCT (owner reports)?

Owners of W246 B-Class cars with the 7G-DCT dual-clutch automatic describe a pause of about a second before the clutch bites when pulling away, and jerking or harsh shifts at low speed. One owner of a high-mileage 2014 B 220 CDI reports judder that a transmission reset did not cu… Severity: medium.

Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.

Data sourced from 680+ owner reports, NHTSA recalls, TSBs, and automotive forums.

Emissions
1
  • Cooling1
  • FAQ

    • What is the 2012-2019 Mercedes-Benz B-Class Electric parking brake fault warning or one side not working (owner reports)?

    W246 owners report a parking-brake malfunction warning, and in one case the electric parking brake worked on one side only. One owner found water in the left rear actuator motor and replaced both actuators, but the warning stayed until the parking-brake control module connectors… Severity: medium.

    What is the 2012-2018 Mercedes-Benz B-Class Diesel particulate filter overloaded warning (owner reports)?

    Owners of W246 OM651 diesel B-Class cars report the engine warning light with a particulate-filter fault. On a 2013 B 200 CDI the fault "particulate filter overloaded" returned after a sustained drive at higher engine speed; on a 2014 B 220 CDI the workshop first found a faulty d… Severity: medium.

    What is the 2012-2019 Mercedes-Benz B-Class Coolant temperature swings or warnings, sometimes from a stuck thermostat (owner reports)?

    Owners of W246 B-Class cars with the M270 petrol engine report coolant warning messages, an engine warning light with the temperature stuck around 70-80 C, or the gauge swinging, with dealers replacing an electronically controlled thermostat that stuck open. Some gauge movement i… Severity: medium.