Peugeot and Citroën Common OBD-II Codes: 308, 508, C4, C5

PSA Group (now Stellantis) unites Peugeot, Citroën, DS, and Opel/Vauxhall. The EP6 THP, EW10/EW12, DW10/DW12 engines are fitted across most models and share characteristic failure patterns.

EP6 THP (1.6 Turbo): The Most Discussed PSA Engine

EP6 THP is a 1.6-litre turbo jointly developed by PSA and BMW (N13/N18 in BMW). Fitted to Peugeot 308/508, Citroën DS3/DS5, Opel Astra J 1.6T.

Known EP6 THP problems:

P0016 — CKP/CMP Synchronisation Failure

Known defect in first-generation EP6 (pre-2012) — VVTi phaser failure.

• Cause: worn VVTi cam gear
• Sometimes resolved by ECU software update
• In severe cases: cam gear replacement (£400–£800)

P0011 / P0014 — VVTi Phase Out of Range

• Clogged OCV (Oil Control Valve)
• On EP6 THP, resolved primarily by flushing and switching to 0W-30

Carbon Deposits on Valves (no code)

EP6 THP is a GDi engine. Carbon buildup appears after 40,000–50,000 miles of city driving.
Symptoms: rough cold idle, misfires when cold, reduced power.

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P0299 — Underboost (EP6 THP)

Common on Peugeot 308 THP and Citroën DS3/DS4 after 50,000–80,000 miles.

Causes:

• Crack in plastic intercooler hose between turbo and intercooler
• Intake manifold gasket leak
• Sticking wastegate (particularly with oil-wetted turbo)

Check:

• Live Data → Boost Pressure Target vs Boost Pressure Actual under load
• Difference > 50 kPa → find the leak

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EGS Robotised Gearbox: Characteristic Problems

Peugeot and Citroën use the EGS (Efficient Gearshift System) robotised gearbox — a standard manual gearbox with a servo clutch actuator.

Common EGS codes:

Code	Description
P0812	Gearbox position sensor: fault
P0700	Transmission: general fault
P0803	1-4 Upshift: incorrect signal
U1118	Lost communication ECU and TCU

Known EGS problems:

• Gearbox stuck in neutral (P0803 + “Gearbox fault” on display)
• Judder pulling away — often resolved by clutch biting point calibration
• Worn clutch actuator after 60,000–80,000 miles

Live Data:

• Clutch Position — 0% (released) to 100% (engaged)
• Gear Position — in neutral: N; if not selecting 1st → actuator problem
• Clutch Wear % — above 80% → replacement or calibration needed

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BlueHDI (DW10/DW12): AdBlue and DPF Codes

Modern Peugeot and Citroën diesels have the full aftertreatment package:

• DPF (Diesel Particulate Filter)
• DOC (Diesel Oxidation Catalyst)
• SCR + AdBlue

Typical codes:

Code	Description
P2002	DPF: efficiency below threshold
P204B	AdBlue: dosing rate too low
P20EE	SCR NOx catalyst: efficiency below threshold
P244B	DPF: differential pressure below threshold

BlueHDI Live Data:

• DPF Soot Load g — when 15–25g → active regeneration starts
• AdBlue Level — at 1.5–2L → refill warning
• SCR Temperature — above 200°C → system active
• Exhaust Temp Before/After DPF — larger difference during regen is normal

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EW20 (2.0 Petrol) and EW10: Common Codes

Peugeot 508, Citroën C5 with 2.0L EW20 petrol:

Code	Description
P0120	Throttle position sensor: open circuit
P0123	Throttle position sensor: high voltage
P0171	Lean mixture Bank 1

Peugeot 508 / Citroën C5 fuel filter: Known blockage issue at 50,000–70,000 miles without replacement → P0087 or pressure drop symptoms.

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Summary Table

Model	Engine	Top Codes
Peugeot 308 II	EP6 THP 1.6T	P0016, P0299, carbon
Peugeot 508 II	EW20 2.0	P0171 MAF, P0420
Citroën DS3/DS5	EP6 THP 1.6T	P0011 VVT, P0299
Peugeot 308 HDI	DW10 2.0 HDI	P2002 DPF, EGS
Citroën C5 Aircross	BlueHDI 2.0	P20EE AdBlue, P2002

PSA vehicles require:

• ECU software updates (especially EP6 Gen 1) — check with Peugeot/Citroën dealer
• Quality 0W-30 oil for EP6 (critical for VVTi)
• Regular AdBlue top-up for BlueHDI diesels