Can an egr issue cause a U1208 ESP fault?

4fvw6lcprxeoyq

So I'm trying to track down the cause of an ESP warning light on my dash. Car is a Peugeot 407 1.6hdi 2006. I'm using Peugeot Planet (or Diagbox depending on my mood) and the fault code I'm getting is U1208 "no communication with engine ECU" and "data invalid".
Thing is, I'm fairly certain there's 'communication' with the engine ecu, I'm reading ~2.5v on the can wires. All my powers and grounds are fine too, and all my abs related values in PP2000 are fine. I can graph everything without fault like: steering wheel angle sensor, wheel speeds, yaw, transverse acceleration, etc.. But as soon as I start the car the fault comes back immediately, if I wipe it with the car started it comes back immediately, so it's not intermittent.

I don't think it's an abs issue either since an abs fault brings up serious red STOP lights on the dash. Cruise control works fine too so that rules out a few other variables.

At the moment I'm thinking it might be related to either the egr or/and a torque-reading issue: PP2000 reads torque (and torque required by driver) as 408nm and it never changes, just a flat line when I graph it. Also, a few of the egr percent values read as negative, like -0.01983 etc.
I'm wondering if the ESP system is multiplying with these negative values to calculate a torque reading, and ending up with a negative number, hence the data invalid error.

The previous owner has blanked off the egr valve, but I don't know if he also removed it from the ecu since I don't have any other car to compare it to. I know lots of people block them off but I assume it doesn't cause an ESP issue every time.

Anyone who knows their stuff got any ideas?

Was going to take the multimeter to the egr today but the weather was manky and it's way down the backside of the engine. I might have a look at it tomorrow and see what it's reading. I need to get rid of the light soon since it failed the NCT due to 'some kind of light on the dash' (lol).

4fvw6lcprxeoyq

So, I'm going to answer my own question: Yes!

I took out the EGR and gave it a clean, and the ESP warning on the dash is now gone, ESP working fine, the U1208 fault code is also gone, and the torque readings are back to normal.
I have the EGR mapped out of the ECU, and tested with the blanking plate on and off and no more faults. I'm guessing the EGR was stuck in a position that the ECU didn't like, and the ECU purposely sent a sent 'wrong' torque signal to the ABS\ESP to deactivate it.
I also got a P1728 (engine ecu torque invalid) fault from the ecu when I flashed a fresh ECU file for testing, that didn't have the EGR mapped out. This would have put me on the right track sooner,:mad: I assume this fault code was mapped out when the egr was getting mapped out to avoid fault codes and check engine lights.

Hope this helps someone in the future.. :-)

dieselbug

The esp system needs good reliable data from the engine to perform correctly and safely, like engine rpm, load etc.

Any fault codes stored by the engine controller make this data unreliable therefore possibly unsafe and the system is disabled bringing on the light.

4fvw6lcprxeoyq

dieselbug wrote: »

The esp system needs good reliable data from the engine to perform correctly and safely, like engine rpm, load etc.

Any fault codes stored by the engine controller make this data unreliable therefore possibly unsafe and the system is disabled bringing on the light.

Yea that sounds about right, when they're values related to the esp anyway. It was sending a constant value of 408nm for 'drivers wish torque' and actual torque. I assume torque is calculated using fuel, engine speed and airflow(which is affected by egr flow). 408 is a strange number to send though.. Maybe a bit of sneaky advertising for the newer Peugeot 408. :-)

I've got a few aunty pollutant faults since blanking the egr again but I can live with that, better than sending dirty air back into the engine..