Oct 202016

A different, non-Linux story today. I own Peugeot 4007 4×4 SUV – a nice car that drives remarkably well and is generally highly regarded by the whole family. I would probably never buy a French car (no offence, my dear French audience) but this one is made in Japan, in the exactly same plant as Mitsubishi Outlander and Citroen C-Crosser. All of these three cars look almost exactly the same, the difference being engine fitted and few details outside. 4007 (AKA four double O seven) and C-Crosser (AKA crossdreser) siblings are fitted with an excellent 2.2 HDI FAP* engine, a powerful and lively unit.

Now, to the point – my engine was seemingly running fine but, as I love tinkering with stuff, I hooked up ELM237 based Bluetooth OBD dongle into diagnostic socket to see if there are any errors recorded. After starting Torque it turned out that there are indeed two faults stored, P1351 and P2408. Googling these faults took me to Peugeot owners forum where it was revealed that

P1351, idm input circuit malfunction,
P2408, fuel cap sensor / switch circuit.


First problem relates to faulty glow plug/plugs. Although it’s quite still warm outside (they aren’t normally needed, only when temp drops to around 0C, allegedly) in this particular engine glow plugs are used to initiate and help with FAP* regeneration cycle, by bringing up temp in exhaust manifold and burn soot accumulated in filter. As far as I understand.

If you are hit with this issue a general advice is to check the relevant relay in engine compartment fuse box first and if that’s OK – replace all four glow plugs. Not so easy to change them if you don’t have a ramp as they sit on the bottom front of the engine. Certainly not a job that can be done on the driveway, besides, glow plugs have a nasty tendency to snap when they’re being removed which turns a simple job into a horror story. I can do simple stuff but this, no thank you. I decided to entrust with this bit to a local garage.

A day later, glow plugs replaced but faults despite clearing are coming back. Hmmm…. OK, lets leave this for now and focus on part two.

Second fault, fuel cap sensor. Why a fuel cap needs a sensor in the first place? It’s because every time you put a diesel into a tank, a tiny amount of special additive (eolys) is being injected into a tank. It helps to lower down fumes burn temperature to assist above mentioned FAP regeneration cycle. Something like that.

Now, how did I fix the second problem? Before diving into locating and replacing this sensor I tried to: check cap to see if there are still two magnets, remove fuel cap, start engine, switched off engine, put the cap back on. Started engine again and went for a short spin to the town. Now the best part. After connecting OBD and running diagnostic again result was: oh my Lord, no stored faults!

Not sure what is logic/magic behind this. I read something that ECU needs some time, few start stop cycles to remove faults. Re fuel cap, maybe ECU lost signal and only removing cap “reset” the system? Anyway, it was somehow related to glow plugs as these problems often show up on Peugeot forums in pairs.

Hope this will help someone who is facing similar problem. Those cars are not so popular, information on the internet are scarce and not very clear. Here with a cheap OBD dongle, cheap Android app I managed to diagnose and solve a problem that would normally result in hefty charge from Peugeot dealer.

* To clarify, stop giggling already – FAP is French for DPF (Diesel Particulate Filter). FAP catches diesel particulates in a silicon carbide filter. It then eliminates them by burning at a high temperature in a ‘regeneration’ process controlled by the engine’s computer.