Problem with Fuel additive and engine ECU

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Matthewscottuk
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Problem with Fuel additive and engine ECU

Post by Matthewscottuk »

Hi everyone!

I have a 2014 1.6L Citroen C4 Grand Picasso that had problems starting.

RAC said it was a weak fuel pump. took it to a Garage said who had to call an electrician out. He said:

“Diagnostics found intermittent fault with SCR system. Fuel additive module has fault with communication to engine ecu.

“Wiring checks done but because of the intermittent fault there was no fault found at the time of tests.

“Its possible for the main SCR tank and module to be at fault but until this fails permanently no diagnoses can be 100 percent.”

The Garage has said to go to the main dealer, who will charge me £312 for diagnostics.

Can anyone help with this please?
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GiveMeABreak
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Re: Problem with Fuel additive and engine ECU

Post by GiveMeABreak »

That's confusing 2 separate technologies and won't be the first time I've heard this.....

The Diesel Particulate Filter (DPF) system is completely separate to the SCR (Selective Catalytic Reduction) system.

1) The DPF uses an additive injected from the Eolys reservoir into the fuel tank each time fuel is added. This is to help reduce the exhaust gas temperature needed to burn of the trapped particles in the DPF during regeneration.

2) Separate to that the SCR system treats the NOx emissions by injecting Urea (Adblue) into the catalytic converter. The Adblue is contained in a separate tank.
Diagnostics found intermittent fault with SCR system. Fuel additive module has fault with communication to engine ecu.
Adblue is not added to the fuel - so they are talking nonsense here.

You may well have a DPF additive pump fault for the Eolys additive, but he seems to be mixing that up in the same sentence as the SCR.
You may also have a fault with the Adblue Tank which contains the Urea pump, or the Urea injector or harness.

So these are separate issues and you need to take it to either a dealer or a proper garage that knows what they are on about to get a proper diagnostic done. Any faults with these systems will generally have fault codes stored that can be retrieved. If you have the actual codes, pop them up here with your VIN and we may be able to help.

Without a proper diagnostic you will be wasting money with garages that don't know what they are doing.

Further, £312 for dealer diagnostics is also BS.

Citroen have a standard hourly rate for diagnostics and it won't take them that long to return the faults. So I don't know where they are getting that from!

£120, see for yourself:

https://www.citroen.co.uk/maintain/fixe ... &gclsrc=ds
Matthewscottuk
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Re: Problem with Fuel additive and engine ECU

Post by Matthewscottuk »

Marc,

Thank you so much for the informative and helpful reply.

I am pursuing the Garage and their electrician for the error codes and will post when I have them.

When RAC got the car started, they did give me an error report with these codes:

DTC: P2291,The rise in pressure in the injection rail is too slow on starting

DTC: P050B,Starting time too long

System Type: ENGINE SYSTEM TEST/VALUES

Name: 9HR - SID 807
DTC: P2291,Rail pressure inadequate at starting

DTC: P050B,Starting time too long

I only seem to have this problem when the car is pointing up hill on my driveway (it’s on a slight incline) and never when facing down hill. It’s also never happened anywhere else…

Hope these codes help and if I find any more I’ll let you know.

Thank you so much again.
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GiveMeABreak
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Re: Problem with Fuel additive and engine ECU

Post by GiveMeABreak »

The main issue is Fault P2291 which is: Starting monitoring: Pressure increase in the injection rail too slow when starting. Fuel injection common rail pressure increase time too long (Threshold at 700 ms when the coolant temperature is 5°C).

The main culprit may be a lack of fuel getting to the high pressure pump and then the rail.

These are the main suspects, but when did you last have the diesel fuel filter changed? If that gets any crap in it from the fuel tank (especially if you regularly run the vehicle with low fuel levels in the tank) this can lead to diesel bugs / sludge or other contamination in the filter and this can cause a fuel supply problem.

Suspects
  • Air leak on the fuel filter
  • Clogging of the fuel filter
  • Running out of fuel
  • Leak in fuel circuit (low pressure)
  • Fuel high pressure flow regulator
  • High pressure fuel pump
  • Leak on the high pressure fuel pipes
  • Leak on the fuel high pressure common injection rail
  • Fuel injectors
  • Electrical harnesses
  • Connectors
So I would first check the diesel fuel filter. However, that must be done properly and the fuel system primed afterwards.
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xantia_v6
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Re: Problem with Fuel additive and engine ECU

Post by xantia_v6 »

It could also be a weak battery or starter causing the engine and hp pump to be cranking too slowly to raise sufficient pressure, the cranking speed should also be checked as part of the diagnostic.
Matthewscottuk
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Re: Problem with Fuel additive and engine ECU

Post by Matthewscottuk »

Thank you both, really helpful.

I’ve been told that there wasn’t an issue with the battery or the fuel filter, so I’m trying to get hold of the electrician to see if he can elaborate any more on his report.

I’m really grateful for all the support shown here!
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GiveMeABreak
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Re: Problem with Fuel additive and engine ECU

Post by GiveMeABreak »

No problem, but I'm not sure how anyone can say you haven't an issue with the fuel filter to be honest - it's not like it will be a different colour...
Matthewscottuk
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Re: Problem with Fuel additive and engine ECU

Post by Matthewscottuk »

The garage finally came back with the following from the electrician:

“Fault code U029D-87 fault code comms with adblue De nox system. Only work for the trade

“Also because it’s intermittent warranty company may not entertain it till it faults constantly”
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GiveMeABreak
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Re: Problem with Fuel additive and engine ECU

Post by GiveMeABreak »

Ok, so that's a completely new code which is a fault with the downstream NOx sensor or communication with it. If the Downstream NOx sensor or is either faulty or not sending data, which in this case the fault indicates the engine ECU is not getting any data, then it means it can't monitor the NOx levels of the exhaust gasses. So it needs further investigation to find out the issue, but here are the pointers. It may of course also mean that the electrical connection to the sensor is faulty which would also cause the lack of data or operation of the sensor.

Fault Code: U029D 87
Description of Fault: Emissions control CAN network (Downstream NOx sensor) : Missing information. Fault in communication with the NOx sensor : Information absent.
Conditions for Fault to clear: At least one of the following conditions must be fulfilled
- After switching the ignition off and then back on
- Driving for 5 minutes
Downgrade Modes whilst Fault is active:
  • Activation of the cruise control or speed limiter function impossible
  • Deactivation/cut-off of the cruise control or speed limiter
  • Switching on of the urea solution warning lamp, then message, then inhibiting of restarting of the engine
    Switching on of the "Stop and Start" warning lamp / Engine diagnosis warning lamp
Symptoms: None Reported
Suspect Areas:
  • Fuse
  • Passenger compartment fuse box
  • Downstream NOx sensor
  • Electrical harness
  • Urea pump - gauge module
  • Connectors
  • Engine ECU
  • DeNOx system relay
  • Supplies protection and management unit