Peugeot 806 OBD2 Fault Codes Explained: P0420, P0201, and P0351-3 Interpretation & Fixes
Hi everyone, I'm looking for reliable guidance on interpreting the OBD2 fault codes appearing on my 2001 Peugeot 80 or 806 (2.0 i, 100 KW, automatic). The current codes are: - P0420: Catalytic Converter System - Bank 1 Efficiency Below Threshold - P0201: Injector 1 - Circuit Malfunction - P0201: Injector 3 - Circuit Low - P0201: Injector 4 - Circuit Low - P0201: Injector 2 - Circuit Low - P0351: Ignition Coil A - Primary/Secondary Circuit Malfunction - P0352: Ignition Coil B - Primary/Secondary Circuit Malfunction The vehicle has been serviced multiple times recently, including replacement of lambda sensors and the catalytic converter. However, the underlying issue remains unresolved. I'm seeking expert input on whether these codes point to a fuel injection problem, ignition coil failure, sensor malfunction, or loose wiring connections. Specifically: - Would replacing injectors or ignition coils resolve the issue? - Is P0420 likely caused by one of the above issues (e.g., misfires), or could it be due to a deeper sensor or system fault? Additionally, the car previously stopped running and would only restart for about 5 seconds. Mechanics initially suspected a fuel pump failure — but I'm now wondering if this might actually point to an electrical or ignition issue. Any insights on how to prioritize diagnostics (e.g., spark testing at plugs, injector circuit checks using a DVOM or noid light) would be greatly appreciated. Best regards, Armand
Yes, OBD2 codes are generally reliable and should be trusted for diagnosis. The P0201 code is not just a broad injector issue — it indicates multiple specific problems: 1) The presence of P0351 and P0352 (ignition coil faults) suggests misfiring, which can directly impact fuel injection performance. 2) The repeated P0201 entries across injectors point to potential circuit issues, especially Injector 1 — this should be checked with a digital multimeter (DVOM) or noid light. 3) P0420 is often triggered by misfires; once the ignition and injector problems are addressed, the catalytic converter efficiency code may clear itself. Recommended next steps: - Confirm spark presence at all plugs — no spark means a serious ignition issue. - Test injectors, especially Injector 1, using a DVOM or noid light to verify proper signal and operation. - Prioritize fixing misfire sources before replacing parts — this will improve diagnostic accuracy and avoid unnecessary component replacements.