IsItAGoodCar
Reliability Guide

Common Problems with the
2021 Peugeot 308 (Mk3)

The P5 308 reached UK dealers in late 2021 with the new lion badge, a 55 mm longer wheelbase and a much plusher cabin. Petrol, diesel, plug-in hybrid and, from 2022, the e-308 electric gave buyers four powertrain routes.

What changed for 2021

  • •1.2 PureTech 130, 1.5 BlueHDi 130 and 1.6 PHEV 180/225 powertrains
  • •Six-speed manual, eight-speed EAT8 and a 12.4 kWh plug-in hybrid battery
  • •e-308 added in 2022 with a 54 kWh battery and 115 kW motor
  • •Matrix LED headlights, 10-inch touchscreen and i-Toggles on GT trim

Common MOT watch-outs

  • !ADAS camera and radar faults after windscreen or bumper repairs
  • !TPMS warnings and uneven tyre wear on 18-inch rims
  • !Brake disc corrosion on low-mileage PHEV and e-308 cars
6
Known Issues
3
Serious
2
Moderate
1
Minor

All Known Issues

1.2 PureTech "Wet Belt" Degradation

SeriousEngine

The 1.2 PureTech petrol engine features an internal timing belt submerged in crankcase engine oil. Fuel dilution and thermal breakdown cause the belt surface to degrade and shed rubber particles into the lubrication circuit. This debris clogs the oil pickup strainer, starving the vacuum pump and resulting in sudden loss of braking servo assistance (Recall R/2020/331), as well as risking terminal engine damage.

Est. Repair Cost: £600–£1,800
Warning Signs:

Low oil pressure warning message displayed on digital cluster, Hard brake pedal requiring excessive foot effort to stop the vehicle, Check engine light illuminated with variable valve timing fault codes, Visible surface cracking, fuzzing, or swelling on the timing belt visible via oil filler cap

What to Inspect:
  • Inspect the timing belt width and surface condition through the oil filler neck using a gauge
  • Verify documented service history proving annual oil changes with correct PSA B71 2010 specification oil
  • Check DVSA database to verify safety recall status and extended 10-year warranty coverage
Verified by IsItAGoodCar Research TeamUpdated

1.5 BlueHDi 7mm Camshaft Chain Snapping

SeriousEngine

Early Mk3 1.5 BlueHDi diesel models built prior to early 2023 use a 7mm chain connecting the twin camshafts. The chain is susceptible to premature wear, elongation, and snapping under load. When the chain breaks, the valves impact the pistons, breaking rocker arms and destroying the camshaft carrier. Stellantis instituted an extended warranty campaign and replacement 8mm chain kit with modified cylinder head components.

Est. Repair Cost: £1,200–£3,500
Warning Signs:

Metallic ticking or clattering noise from upper cylinder head during cold startup, Sudden engine shutdown while driving followed by refusal to restart, Engine spins rapidly and evenly on starter motor with zero cylinder compression, Check engine warning light accompanied by camshaft synchronization DTCs

What to Inspect:
  • Listen for metallic clattering from the top right of the cylinder head on a cold start
  • Confirm with dealer service records whether the 8mm chain upgrade has been fitted under warranty
  • Check service documentation proving strictly observed 0W-20 (PSA B71 2010) engine oil changes
Verified by IsItAGoodCar Research TeamUpdated

Plug-in Hybrid (PHEV) Traction Battery and On-Board Charger Faults

SeriousElectrics & Electronics

The Hybrid 180 and Hybrid 225 plug-in hybrid models utilize a 12.4 kWh high-voltage lithium-ion battery pack and an integrated on-board charger (OBC). Owners experience unexpected charging halts, charging port locking errors, failure to engage pure Electric mode, and high-voltage isolation fault messages. Rectification requires high-voltage BMS software flashes or physical OBC replacement.

Est. Repair Cost: £600–£2,400
Warning Signs:

Instrument cluster displays "Electric mode currently unavailable" when selected, Charging port LED blinks red and AC charging session disconnects after a few minutes, High-voltage traction electrical fault message illuminated on digital instrument cluster, Traction battery fails to charge beyond minimal level on home wallbox

What to Inspect:
  • Plug vehicle into a Type 2 AC charger and verify continuous charging without disconnection
  • Select pure Electric mode on test drive and check that the petrol engine remains dormant under moderate throttle
  • Verify whether dealer technical service bulletins relating to PHEV battery management have been completed
Verified by IsItAGoodCar Research TeamUpdated

Infotainment & i-Cockpit Software Bugs

ModerateElectrics & Electronics

The Peugeot i-Connect and i-Connect Advanced infotainment system on Mk3 models suffers from software instability. Owners experience blank black screens, sluggish menu navigation, freezing digital i-Toggle shortcut bars, and dropped wireless Apple CarPlay and Android Auto connections. Dealership firmware updates are required to resolve system crashes and restore responsive touch control.

Est. Repair Cost: £0–£350
Warning Signs:

Central 10-inch infotainment touchscreen blackouts or random reboots while driving, Configurable digital i-Toggles strip fails to respond to touch or freezes in one mode, Repeated wireless Apple CarPlay or Android Auto connection dropouts, Climate control temperature sliders lag or fail to adjust cabin fan speed

What to Inspect:
  • Operate all configurable i-Toggle shortcuts and swipe through vehicle setup menus for lag
  • Connect a smartphone to verify wireless Apple CarPlay and Android Auto stability
  • Confirm with a Peugeot franchised dealer that the telematics software has been updated to the latest release
Verified by IsItAGoodCar Research TeamUpdated

12-Volt Auxiliary Battery Discharge and Phantom Drain

ModerateElectrics & Electronics

The complex networked electronics, telematics module, and proximity keyless entry on the 308 Mk3 create significant parasitic battery drain when parked. If left standing or driven primarily on short urban runs, the 12V auxiliary battery quickly drains below minimum operating voltage, locking out electronic systems and generating multiple false ADAS and stability warnings on startup.

Est. Repair Cost: £140–£320
Warning Signs:

Vehicle fails to unlock via proximity sensor or start without a jump pack, "12V battery low" warning or vehicle enters permanent Economy Mode shutdown, Spurious dashboard warnings for lane assist, front radar, and electronic parking brake, Starter motor clicks repeatedly without cranking the engine

What to Inspect:
  • Test auxiliary 12V battery open-circuit voltage with a multimeter before starting
  • Verify how rapidly central displays initialize when unlocking the driver door
  • Check whether telematics control unit sleep-mode firmware updates have been installed
Verified by IsItAGoodCar Research TeamUpdated

Front Radar and ADAS Sensor Calibration Drift

MinorElectrics & Electronics

The forward-facing radar mounted behind the front grille badge and the camera module mounted in the upper windscreen can lose alignment from minor bumper impacts, road grit, or windscreen replacements. Misalignment causes adaptive cruise control, automatic emergency braking, and active lane keeping to disable intermittently with persistent cluster warnings.

Est. Repair Cost: £200–£550
Warning Signs:

"Front radar sensor blinded" or "Driving aids unavailable" alert displayed in clear weather, Adaptive cruise control disengages abruptly or refuses to activate on dual carriageways, Lane positioning assist wanders within lane or gives false lane-departure tugs, False forward collision emergency alerts triggered by roadside guardrails or bridges

What to Inspect:
  • Examine the front grille badge and windscreen camera aperture for physical damage, stone chips, or misaligned brackets
  • Test adaptive cruise control and lane keep assist systems during a road test
  • Confirm whether the windscreen has been replaced and whether optical calibration was performed
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 2021 Peugeot 308 (Mk3)

  • Test every i-Toggle and the touchscreen climate page for lag
  • On PHEV, check the charge flap, both cables and the petrol engine's cold start
  • Verify the software version with a dealer before buying an early 2021-2022 car
2022–2023
Check a 2021 Peugeot 308 (Mk3) by Registration