OBD Code - P0420 / P0201 / P351 - what is the likely cause?

Question

Hi,

I would really appreciate some help with interpretation OBD codes showing up om my Peugeot 806, 2001, 2.0 i, 100 KW, automatic

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
P0420, Catalytic Converter system, bank 1, efficiency below threshold

The car has been in and out of the garage recently but they do not seem to be able to fix whatever is the problem. Lambda sensors and other sensor are recently changed (and also the catalytic part of the exhaust). Would appreciate if somebody could comment on the codes shown above and advice if e.g. replacing injectors and ignition coil would solve the problem (or this is more likely to be a sensor problem or loose connection problem). The car stopped a while back and would after restart it would only run for about 5 sec. "Experts" though this was a problem with the fuel pump.

All the best, Armand

Answer 1

The fact that the car has been stopping and restarting indicates that there is a problem with the fuel delivery system. This could be due to a faulty fuel pump, a clogged fuel filter, or a problem with the injectors.

It is difficult to say definitively what the problem is without more information, but it is possible that all of these codes are related to the same underlying issue. For example, if the fuel pump is not delivering enough fuel, this could cause the injectors to malfunction and the ignition coils to misfire. This could also lead to a buildup of carbon deposits in the catalytic converter, which would cause the P0420 code.

I recommend that you take your car to a qualified mechanic who has experience with Peugeot vehicles. They will be able to diagnose the problem and recommend the appropriate repairs.

Here are some things you can do to try to troubleshoot the problem:

• Check the fuel pressure. If the fuel pressure is too low, this could be a sign of a faulty fuel pump or clogged fuel filter.
• Check the injector resistance. If the injector resistance is too high or too low, this could be a sign of a faulty injector.
• Check the ignition coil resistance. If the ignition coil resistance is too high or too low, this could be a sign of a faulty ignition coil.
• Check the wiring harness for any signs of damage.
• Check the ECU for any signs of damage.