Fuel Cap Open error

[exec406]

Hi

I have a 406 2.2 diesel (2003) and have just had a new DPF fitted (main dealer) and also had the additive fluid topped up with counters reset. I also had a replacement fuel cap sensor fitted.

At the same time, I also got a new ECU controller fitted for the additive tank.

After all that, I'm still getting problems with a 'fuel cap open message' after about 20 minutes or so of the car running. When starting from 'cold' e.g. overnight, I don't get the fuel cap open message but after about that 20 minute time frame, it comes on all the time when you stop the car with the engine running.

Before the car went into the main dealer to get a new DPF etc the 'min level gasoil' was constantly on and 'Clean diesel filter urgent' message was more or less constant and every other day I had to take the car a blast at 60mph, only for the blocked filter message to come back after about a day or so. I also had the fuel cap open error but it was more frequent than it is now.

Does anyone know how I can get this 'fuel cap open' issue fixed? Mechanic at the main dealer suggested fuel cap magnets were not that strong and to try another cap off E-Bay (these magnetic fuel caps are no longer produced for the 406) I managed to get another cap off a 607 with the 2.2 and the fuel cap open message is replicated again after about 20 minutes.

Could a dodgy differential pressure sensor be causing this? Could it have been goosed when I had the blocked DPF? Could it be some other electrical system that's cutting power to the fuel cap sensor? When plugged into a OBDII adapter using the Torque app these codes come up:

P1446
P2408
P1442

Any help appreciated! Car does not go into limp mode on these errors.

Not looking to De-Fap after spending quite a bit of cash on this new DPF etc.

[Doggy]

The only thing I can think of trying is to use PP2000 to show the status on the fuel flap sensor, while you manipulate, tap, wiggle or pull everything in sight until you find out what's causing it.
There's a diagram on here: http://petrila.org/repair/index.htm
The switch links pin 19 of the 26-way yellow connector on the BSI, (wire no. 4201) to ground or not, depending on whether the cap's fitted.
If you can't get reliable operation of the reed switch, you could always wire it to a pushbutton inside the car and press it yourself when you refuel.

I can understand you not wanting to de-FAP after spending all that money, but bear in mind it will need doing again... and again... and again

[exec406]

Thanks for that, I'll get the car back in again soon.

In the interim, don't think I'll drive it that much as that fuel cap open coming on all the time after about 20mins is sure to drain the Eolys fluid quickly?

Apart from the new fuel cap sensor just fitted, the car had another fuel cap sensor put on about four years ago. At that time it was a straight 'fuel cap open' as soon as you started the car, not a 20 mins or so delay like this time around.

The build up to the fuel cap error before I had the car booked in was the min level gasoil message came on and I was driving about having to do almost daily fast runs at high revs to clear the FAP blocked message as well. I did this for quite a while and it was during that time the fuel cap open message started. This is what lead me to believe is that a blocked FAP being driven for a while could cause damage to the differential pressure sensor.

If the differential pressure sensor near the FAP was on the blink what issues would I have?

I also thought it could even be a faulty brake light switch that was causing the issue as occasionally I would get the ESP/ABS light coming on. The fact I'm getting the fuel cap open error when I'm just off or just on the brakes coming to a stop led me to think that. Perhaps the fuel cap open error doesn't flash up at certain speeds?

Cheers

[Doggy]

Be aware it's generally not soot that blocks the FAP, as this burns away during a successful regen, but the additive residue never clears and it is this that ultimately blocks the filter.

If the differential pressure is too high, you will get a FAP warning light, EML, A/P fault and 'unblock diesel filter' messages. In extreme cases it wil go into one of several limp modes. Normally you will experience difficulty starting as well.

[exec406]

Be aware it's generally not soot that blocks the FAP, as this burns away during a successful regen, but the additive residue never clears and it is this that ultimately blocks the filter.

If the differential pressure is too high, you will get a FAP warning light, EML, A/P fault and 'unblock diesel filter' messages. In extreme cases it wil go into one of several limp modes. Normally you will experience difficulty starting as well.

Thanks for that.

Turned on the engine this morning and I had the ESP/ABS error lights coming on but no fuel cap open error.

Later in the day I had those errors plus the Fuel Cap open message at same time when starting the car. The ESP/ABS error then went away but the fuel cap open error remained.

Will this multiple fuel cap open message drain the Eolys rather rapidly?

Cheers

[GingerMagic]

When I got my MK1 Gingermobile, I drove it from Dudley to Bournemouth in limp-mode with the fuel flap beeping every time I pulled away, either from lights or just in traffic - I was on the brink of madness after a 6 hour journey...
No ABS fault though, just the Flap open one so I don't think your faults are connected.

I used to think this drained the additive quickly too, but I believe there is also another way of the ECU knowing whether you have refueled or not, although I can't remember off the top of my head.

[MixMan]

I believe the fuel gauge sender messages the ECU, hence why you have to put fuel in when resetting the counters after filling the Eloys fluuid up.

[Doggy]

Agreed. On starting, the additive ecu looks for an increase in fuel tank contents of something like 10 - 15 litres or more as part of its decision process regarding when and how much additive to inject. It is likely the strategy and programming evolved during the 3 years or so that dpf equipped 406's were produced. There was certainly a change in additive type and quite possibly improvements to overcome issues identified on the earlier cars. For this reason you will find conflicting accounts of how the system works and the precise role of the fuel cap sensor and / or fuel gauge.

[exec406]

Thanks for that.

I was under the impression every time the system sensed no fuel cap it assumed fuel was being added and would inject the Eolys 176. But, considering the keys are usually out of the ignition at that point there would be no power to the cap sensor anyway?

If the system senses the fuel level change and adds additive then that's a bit of a relief the Eolys is not going to go down pronto with that fuel cap message flashing all the time.

I had a new additive ECU fitted the other week. How does that work exactly - does it communicate with the fuel sender gauge & the DPF sensors?

May have to get another (new) fuel cap sensor and take it from there.

Cheers

[Doggy]

The keys being out of the ignition doesn't gaurantee 'grand frere' isn't watching you - the various ecus shut down over a period of some minutes when you turn off.

You have a 'fully-multiplexed' electrical system, which means all the ecus communicate and share information. (This means you can use one coolant temperature sensor to work the gauge, control the fans and give values to the engine ecu, for example).

The additive ecu is responsible, among other things, for adding Eolys to the fuel tank, but requests regeneration assistance from the engine ecu, the engine ecu will request assistance from the BSI, which turns on as many electical loads as possible to increase engine load to help increase exhaust temperature to assist burning off the soot trapped in the dpf during regeneration and so on.

Your fuel cap sensor is connected to the BSI, not the additive ecu. The problem may not be related to the additive ecu at all.

[exec406]

Thanks for the info.

If the fuel cap open error has no impact on the injection of the Eolys 176, can I not just disable this fuel cap open message somehow?

Could you do it via Peugeot Planet? Or just disconnect the cap sensor itself?

It's a new sensor that's on and if I get another new sensor I might have the same problem. Or maybe it would be wiser to get if fixed?

Also:

Why do I get P1446 & P1442 error codes appearing at the same time when the cap error (P2408) appears? Are they linked to P2408?

Thanks for the help.

[exec406]

.....it appears the P1446 can't be cleared whilst the fuel cap error P2408 is showing as I found on this thread here:

http://www.peugeotforums.com/forums/307 ... des-23052/

Main dealer was saying they couldn't clear a low additive fault code (which I presume was the P1446) and they had just filled up the Eolys.

Think I need to get another new cap sensor again....

[GingerMagic]

The codes are;

P1446 - Evaporative Vac Solenoid Circuit Malfunction
P2408 - Fuel Cap Sensor/Switch Circuit

I'm not sure how the P1446 affects the other code and why it can't be cleared...?

I think Planet can turn off the sensor, or make it 'absent' but there may be other factors to consider..

[Doggy]

The common reason you can't clear a low additive level fault is because the level sensor has burned out. The sensor is a thermistor that is 'cooled' by the additive it's immeresed in and measures an increase in temperature when it's uncovered. If it is left uncovered for any length of time, the thermistor burns out and is not available separately, so you need a new tank.

Be good if they told you this before charging you for filling it up, wouldn't it?

[exec406]

The common reason you can't clear a low additive level fault is because the level sensor has burned out. The sensor is a thermistor that is 'cooled' by the additive it's immeresed in and measures an increase in temperature when it's uncovered. If it is left uncovered for any length of time, the thermistor burns out and is not available separately, so you need a new tank.

Be good if they told you this before charging you for filling it up, wouldn't it?

Cheers

£241 for a new additive tank.

I wonder if the two additive related error codes P1442 & P1446 are programmed to use the fuel cap sensor alert as a way of 'notifying' about this error as those codes are not limp codes.

I'm sure main dealer technician sad he tested the new cap sensor and it was OK and the fact I've now tried a different fuel cap and have the same error leads me to think this could be the case.

If I get this job done I wonder if they could get the full tank of eolys fluid out of the old tank into the new one rather than paying for 4 or 5 litres eolys again.

Thanks