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PSA Group
🟡 Medium
PSA Group
P0420
PSA P0420 Catalyst System Efficiency Below Threshold
The P0420 diagnostic trouble code indicates an issue with the Catalyst System Efficiency Below Threshold. A notorious code on Peugeot/Citroen (PSA) vehicles, mainly resulting from worn or melted catalytic converter. Found frequently across psa models utilizing 1.6 HDi, PureTech, THP engines, this code will illuminate the Check Engine Light and may cause the vehicle to enter Limp Mode to protect the mechanical components.
Brand
PSA Group
Fault Code
P0420
Severity
🟡 Medium
Models
Peugeot 207/208/3008/5008, Citroën C3/C4/C5, DS3/DS5
🛠️ Diagnostic Overview
Difficulty Level
🛠️🛠️🛠️
Hard (Advanced)
Estimated Time
⏱️ 3-6 Hours
🧰 Required Tools
- ✓ Digital Multimeter
- ✓ OBD2 Diagnostic Scanner
- ✓ Socket Wrench & Hand Tools
- ✓ Electrical Contact Cleaner Spray
⚠️ Possible Causes
- • Worn or melted catalytic converter
- • Faulty wiring harness connecting the respective sensor
- • Aging electrical connections or corrosion due to environmental elements specific to psa vehicles.
🔧 Recommended Fixes
- → Conduct a complete OBD2 scan. Inspect the engine bay for loose connections related to Catalyst System Efficiency Below Threshold. Replace failed components with genuine OEM psa parts to ensure the fault does not return. Clear the ECU memory afterwards.
🚗 Commonly Affected Vehicles
🏭 PSA Group – Other Common Fault Codes
U0100
PSA U0100 Lost Communication With ECM/PCM A
🚨 Critical
B1000
PSA B1000 Airbag Control Module Fault
🟡 Medium
P2293
PSA P2293 Fuel Pressure Regulator 2 Performance
🔴 High
P2279
PSA P2279 Intake Air System Leak
🟡 Medium
P219A
PSA P219A Bank 1 Air-Fuel Ratio Imbalance
🟡 Medium
P2181
PSA P2181 Cooling System Performance
🟡 Medium
P2096
PSA P2096 Post Catalyst Fuel Trim System Too Lean
🟡 Medium
P2015
PSA P2015 Intake Manifold Runner Position Sensor Circuit Range
🔴 High
P1101
PSA P1101 MAF Sensor Out of Self Test Range
🟡 Medium
P0741
PSA P0741 Torque Converter Clutch Circuit Performance
🟡 Medium
P0700
PSA P0700 Transmission Control System Malfunction
🚨 Critical
P0600
PSA P0600 Serial Communication Link Malfunction
🟡 Medium
P0507
PSA P0507 Idle Control System RPM Higher Than Expected
🟡 Medium
P0500
PSA P0500 Vehicle Speed Sensor Malfunction
🟡 Medium
P0456
PSA P0456 EVAP System Leak Detected (very small leak)
🟡 Medium
P0455
PSA P0455 EVAP System Leak Detected (large leak)
🟡 Medium
P0442
PSA P0442 EVAP System Leak Detected (small leak)
🟡 Medium
P0441
PSA P0441 Evaporative Emission System Incorrect Purge Flow
🟡 Medium
P0430
PSA P0430 Catalyst System Efficiency Below Threshold Bank 2
🟡 Medium
P0400
PSA P0400 Exhaust Gas Recirculation Flow Malfunction
🟡 Medium
P0335
PSA P0335 Crankshaft Position Sensor A Circuit Malfunction
🔴 High
P0325
PSA P0325 Knock Sensor 1 Circuit Malfunction
🟡 Medium
P0304
PSA P0304 Cylinder 4 Misfire Detected
🟡 Medium
P0303
PSA P0303 Cylinder 3 Misfire Detected
🟡 Medium
P0302
PSA P0302 Cylinder 2 Misfire Detected
🟡 Medium
P0301
PSA P0301 Cylinder 1 Misfire Detected
🔴 High
P0300
PSA P0300 Random/Multiple Cylinder Misfire Detected
🚨 Critical
P0299
PSA P0299 Turbocharger Underboost Condition
🚨 Critical
P0234
PSA P0234 Turbocharger Overboost Condition
🚨 Critical
P0175
PSA P0175 System Too Rich Bank 2
🟡 Medium
P0174
PSA P0174 System Too Lean Bank 2
🔴 High
P0172
PSA P0172 System Too Rich Bank 1
🟡 Medium
P0171
PSA P0171 System Too Lean Bank 1
🔴 High
P0141
PSA P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
🟡 Medium
P0135
PSA P0135 O2 Sensor Heater Circuit Malfunction
🟡 Medium
P0133
PSA P0133 O2 Sensor Circuit Slow Response
🟡 Medium
P0130
PSA P0130 O2 Sensor Circuit Malfunction
🔴 High
P0128
PSA P0128 Coolant Thermostat Malfunction
🟡 Medium
P0113
PSA P0113 Intake Air Temperature Circuit High Input
🟡 Medium
P0102
PSA P0102 Mass Air Flow Circuit Low Input
🟡 Medium
P0101
PSA P0101 Mass Air Flow Sensor Circuit Range/Performance
🟡 Medium
P0088
PSA P0088 Fuel Rail/System Pressure - Too High
🟡 Medium
P0016
PSA P0016 Crankshaft Position - Camshaft Position Correlation
🚨 Critical
P0012
PSA P0012 A Camshaft Position Timing Over-Retarded
🟡 Medium
P0011
PSA P0011 A Camshaft Position Timing Over-Advanced
🟡 Medium
P0010
PSA P0010 A Camshaft Position Actuator Circuit
🟡 Medium
P0340
CMP Sensor Signal Fault (TU/EW Petrol Engines)
🔴 High
U1213
BSI Internal Fault / Communication Failure
🔴 High
P0401
EGR Insufficient Flow (HDi DV4/DV6/DW10 Diesel)
🟡 Medium
P2187
System Too Lean at Idle (THP 1.6 Prince Engine)
🟡 Medium
P0087
Fuel Pressure Too Low (HDi Common Rail Diesel)
🔴 High
P2002
DPF (FAP) Efficiency Below Threshold (HDi Diesel)
🔴 High
P1336
Crankshaft Position Sensor Adaptation Required
🔴 High
P1336
PSA P1336 Crank/Cam Adaptation Fault
🔴 High
P0087
PSA P0087 High Pressure Fuel Rail Low
🔴 High
P1434
PSA P1434 Additive System Fault
🔴 High
P1435
PSA P1435 Additive System Level Error
🔴 High
P0299
PSA P0299 HDi Underboost
🔴 High
P0171
PSA P0171 PureTech Lean Mixture
🔴 High
P0100
PSA P0100 MAF Signal Incoherent
🔴 High
BSI-01
PSA BSI-01 BSI Supply Error
🔴 High
P1160
PSA P1160 Intake Air Leak
🔴 High
P0032
PSA P0032 HO2S Heater Control Circuit High (Bank 1 Sensor 1)
🚨 Critical
P0037
PSA P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
🚨 Critical
P0038
PSA P0038 HO2S Heater Control Circuit High (Bank 1 Sensor 2)
🚨 Critical
P0051
PSA P0051 HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
🔴 High
P0057
PSA P0057 HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
🟡 Medium
P0058
PSA P0058 HO2S Heater Control Circuit High (Bank 2 Sensor 2)
🟢 Low
P0103
PSA P0103 Mass or Volume Air Flow Circuit High Input
🚨 Critical
P0107
PSA P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
🟡 Medium
P0108
PSA P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input
🔴 High
P0112
PSA P0112 Intake Air Temperature Circuit Low Input
🟡 Medium
P0117
PSA P0117 Engine Coolant Temperature Circuit Low Input
🚨 Critical
P0118
PSA P0118 Engine Coolant Temperature Circuit High Input
🟡 Medium
P0122
PSA P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low Input
🟡 Medium
P0123
PSA P0123 Throttle/Pedal Position Sensor/Switch A Circuit High Input
🟢 Low
P0125
PSA P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
🟡 Medium
P0131
PSA P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
🟡 Medium
P0132
PSA P0132 O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
🚨 Critical
P0134
PSA P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
🟢 Low
P0137
PSA P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
🔴 High
P0138
PSA P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
🔴 High
P0151
PSA P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
🟡 Medium
P0152
PSA P0152 O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
🚨 Critical
P0157
PSA P0157 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
🟢 Low
P0158
PSA P0158 O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
🟢 Low
P0200
PSA P0200 Injector Circuit Malfunction
🔴 High
P0231
PSA P0231 Fuel Pump Secondary Circuit Low
🟡 Medium
P0232
PSA P0232 Fuel Pump Secondary Circuit High
🚨 Critical
P0327
PSA P0327 Knock Sensor 1 Circuit Low Input (Bank 1 or Single Sensor)
🟡 Medium
P0328
PSA P0328 Knock Sensor 1 Circuit High Input (Bank 1 or Single Sensor)
🟡 Medium
P0332
PSA P0332 Knock Sensor 2 Circuit Low Input (Bank 2)
🔴 High
P0333
PSA P0333 Knock Sensor 2 Circuit High Input (Bank 2)
🟡 Medium
P0440
PSA P0440 Evaporative Emission Control System Malfunction
🚨 Critical
P0443
PSA P0443 Evaporative Emission System Purge Control Valve Circuit
🟡 Medium
P0446
PSA P0446 Evaporative Emission System Vent Control Circuit Malfunction
🔴 High
P0451
PSA P0451 Evaporative Emission System Pressure Sensor Range/Performance
🟡 Medium
P0452
PSA P0452 Evaporative Emission System Pressure Sensor Low Input
🟢 Low
P0453
PSA P0453 Evaporative Emission System Pressure Sensor High Input
🔴 High
P0462
PSA P0462 Fuel Level Sensor Circuit Low Input
🔴 High
P0463
PSA P0463 Fuel Level Sensor Circuit High Input
🔴 High
P0502
PSA P0502 Vehicle Speed Sensor Circuit Low Input
🟡 Medium
P0503
PSA P0503 Vehicle Speed Sensor Intermittent/Erratic/High
🔴 High
P0505
PSA P0505 Idle Control System Malfunction
🟢 Low
P0506
PSA P0506 Idle Control System RPM Lower Than Expected
🟢 Low
P0562
PSA P0562 System Voltage Low
🚨 Critical
P0563
PSA P0563 System Voltage High
🟡 Medium
P0601
PSA P0601 Internal Control Module Memory Check Sum Error
🚨 Critical
P0603
PSA P0603 Internal Control Module Keep Alive Memory (KAM) Error
🟢 Low
P0604
PSA P0604 Internal Control Module Random Access Memory (RAM) Error
🔴 High
P0605
PSA P0605 Internal Control Module Read Only Memory (ROM) Error
🟢 Low
P0606
PSA P0606 ECM/PCM Processor Fault
🟢 Low
P0705
PSA P0705 Transmission Range Sensor Circuit Malfunction (PRNDL Input)
🟡 Medium
P0706
PSA P0706 Transmission Range Sensor Circuit Range/Performance
🟡 Medium
P0715
PSA P0715 Input/Turbine Speed Sensor Circuit Malfunction
🟢 Low
P0720
PSA P0720 Output Speed Sensor Circuit Malfunction
🟢 Low
P0722
PSA P0722 Output Speed Sensor No Signal
🔴 High
P0731
PSA P0731 Gear 1 Incorrect Ratio
🚨 Critical