Technical Fiat Ducato

[bengoa]

Hello all! hoping somebody can help us.


We have a Fiat Ducato 2.3 from 2014 (pre-facelift X250), converted to a camper-van. We are in Italy (we have been stranded here because of the covid lockdowns and finally returning home) and two weeks ago after a cold start the engine would not rev up and vibrates strongly while idling, the engine stops after a few seconds and the engine management light comes on. The logged code is P0697, I could only find two other threads searching for the error code, neither posted the solution.

If I press the accelerator while switching the engine on, then works as long as I keep pressing the accelerator. Once the engine is warm it works, starts and idles fine without having to press the accelerator.

After a trip to the mechanic, they reset the ECU and it worked fine, until now when it happens every time I start. I have taken it to 5 other mechanics, but they find it hard to diagnose because it only happens when cold and can't do much apart from resetting the ECU.


I can't find exactly what sensors are related to this ECU (edc16c39) anywhere

So far I have tried to check the cables from the sensor to the ECU, but my multimeter leads don't fit in the ECU connector pins (we are traveling so we don't have many tools). Last year we had a similar symptoms when a broken EGR pipe caused the DPF to become clogged, so I tried changing the DPF differential pressure sensor without luck.


Does anybody know exactly what sensors are related to this error code?

Would really appreciate any kind of help diagnosing this.

 

[FreeSpirit]

Hi
Try this site which has the error codes for Fiat & other makes -
https://www.dtcdecode.com/

Here is a direct link to the Fiat code P0697 :
https://www.dtcdecode.com/FIAT/P0697

FIAT DTC P0697
Make:FIAT
Code0697
Definition:
Sensor Reference Voltage 3 Circuit
Description:
The Powertrain Control Module (PCM) detects a short to voltage or short to ground on the 5-Volt Sensor Supply 3 circuit for 0.6 seconds.
Cause:
•5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
•5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
•FUEL TANK PRESSURE (FTP) SENSOR
•A/C PRESSURE SENSOR
•POWERTRAIN CONTROL MODULE (PCM)

Hope this helps
Cheers

 

[bengoa]

Hey, Sorry, the ECU is MJD 8F3.B1, not the bosh one.

I already found that page before and tried disconnecting the A/C pressure sensor (no luck), trying to diagnose the problem but can't find the pinout of the ECU anywhere.

It was a lof of head scratching because I was testing cables using the bosh pinout (they have the same connectors) and I was going crazy thinking my multimeter leads weren't contacting the pins in the ECU connector correctly.

Anyone have a wiring diagram or pinout of the MJD 8F3.B1 ecu? I can't find anywhere.

 

[bengoa]

We spent all day debugging it today,
First we found the pinout, for the people that arrive here via search, I'm not allowed to post links, but you can find it by searching for "ducato 2.3 euro 5" in google books, there is one Italian book there called "Manuale di riparazione elettronica Fiat Ducato 2.3 JTD (130 e 150 cV) - EAV77" you can find the pinout in page 19. It's in Italian, but it was easy for me to understand.


Then we tested the continuity of the cables to the sensors (everything we tested was fine), but when we tested the voltage some of the 5V supply wires show 1.2V instead. We started disconnecting all sensors that are supplied by 5V until the voltage was fixed and found out the problem is only present when the DPF differential pressure sensor is connected. I just changed this sensor trying to troubleshoot the problem and it happens both with the new one and the old one.

So if the sensor is not broken does that mean that the ECU is broken? Any other idea?

 

[andydiver]

You are doing all the right sorts of things only using buzz testing to find an intermittent wiring issue is hit and miss at best and unlikely to find the issue as such. Removing and replacing lots of connections has not so far fixed the issue by disturbing and friction, nor changing sensors?
There are more connections under the headlight on the air filter side, around the Ecu and in a big plastic box affair tucked in that area.
Keep going, and use visual inspection to look fir hints of corrosion and so on in the connection blocks, some of them are quite big multiway affairs.
Also keep an eye for heavier looking earth wires, scrub any you find.
Good luck.
It is also worth putting the battery on charge overnight, you never know, you might be getting brown outs on the voltage line.

 

[rayc]

Then we tested the continuity of the cables to the sensors (everything we tested was fine), but when we tested the voltage some of the 5V supply wires show 1.2V instead. We started disconnecting all sensors that are supplied by 5V until the voltage was fixed and found out the problem is only present when the DPF differential pressure sensor is connected. I just changed this sensor trying to troubleshoot the problem and it happens both with the new one and the old one.

So if the sensor is not broken does that mean that the ECU is broken? Any other idea?

A voltage that drops when a load is connected indicates a high resistance, possibly somewhere in the feed to it. It is a bit complicated that the 5v is ok with all other sensors fitted but it drops to all of them when the dpf pressure sensor is connected. What is the resistance of the sensor and what happens if a resistor of similar value is inserted in its place?

 

[bengoa]

Removing and replacing lots of connections has not so far fixed the issue by disturbing and friction, nor changing sensors?

We can reproduce the voltage drop problem every time, we tried disconnecting the sensor several times, only happens when the sensor is connected. I had a look at all the cables I could see, but that was before I figured out the voltage drop. Will try to follow the DPF pressure sensor cables to the ECU tomorrow and see if I can see something fishy.

A voltage that drops when a load is connected indicates a high resistance, possibly somewhere in the feed to it. It is a bit complicated that the 5v is ok with all other sensors fitted but it drops to all of them when the dpf pressure sensor is connected. What is the resistance of the sensor and what happens if a resistor of similar value is inserted in its place?

We will check the resistance of the cables going to the sensor and the resistance of the sensor tomorrow, not sure if I can find a shop to buy a resistance here but we will try! Thanks for the suggestions

 

[bengoa]

The three cables are fine, the resistance between the pins of the sensor is (with the sensor disconnected from pipes so 1atm in both pipes)

Ground to Supply 23 Ohm
Ground to Signal 51 Ohm
Signal to Supply 59 Ohm

I don't know enough about this to know if it's normal or what.

 

[JohnCamper]

I am at exactly the same stage as you with what appears to be exactly the same problem.
2013 Ducato motorhome. 130 Multijet.

Never had any issue before.
Engine warning light came on during a long drive, plus cruise control stopped working, but I think that's a consequence, not a fault.

Starting the engine - idle is rough, and stalls after some seconds.
Start engine with some throttle and it runs fine once "warmed up"
Took to a local friendly garage who plugged it in.
Fault shown as DPF clogged, and Cruise Control intermittent.
He cleared the fault codes. Ran perfectly for a minute, then engine warning light came back on, and back to same problem as before clearing.
I have reason to believe the DPF is NOT clogged, so removed the pressure sensor to inspect.
Found water present inside the sensor when tapped it into my hand. Apparently this is evidence of a damaged sensor.

Ordered a new one yesterday. Waiting for delivery.
Be sure to blow out the connected pipes from the DPF, or you may water-damage a new sensor, I've been told.
I'm also in the process of setting myself up with MultiECUscan so I can help myself a bit more.
Please do let me know how you get on, as we do seem to have the same problem.

 

[Anthony489]

Hi Bengoa

I don't have access to detailed manufacturer's data, so what follows is my educated guess.


You have three sensors which all share the same +5 Volt supply. I would expect this supply to be regulated down within the ECU from the vehicles 12V supply and then sent out to the three sensors. It would normally only be expected to supply a fairly small total current, say 30 milliamps (10 milliamps per sensor), and may have inbuilt electronic short circuit protection/current limiting rather than a fuse. In this case, any overload causes the voltage to progressively collapse down, in your case this seems to be happening when the Differential Pressure Sensor (DPS) is connected.

The electronic chip within the DPS will produce an analogue voltage signal for the ECU, from which it can calculate the pressure drop across the DPF to tell if it is excessively restricting flow (blocked). This analogue signal would normally be in the range +0.5 to +4.5 volts relative to ground. Anything below about +0.2 V or above +4.8 V will be treated by the ECU as a fault.


Your DPS resistance readings look rather low to me, but to be honest resistance checks on electronic circuits can be a bit hit and miss, and can be different depending on which way round you place the meter probes. I have read reports of faulty sensors filling with water and thereby drawing excessive current, though this wouldn't explain your replacement sensor showing the same behaviour. The DPS input tubes must face down to keep condensation out of the sensor. What resistances does the new sensor show, measured both ways round ?


I can see four possibilities 1.) The DPS is drawing more supply current than it should. 2.) One of the other two sensors is drawing more current than it should, and adding the DPS is the "last straw" 3.) The connectors and wiring of the 5V supply from the ECU have excessive series resistance. 4.) The ECU for some reason is incapable of supplying enough current

I hope this information might shed some light on your faultfinding, I appreciate it's not easy with limited equipment.

Good luck, and keep us posted.

One last thought, if you keep the old DPS in place with its tubes, but temporarily wire in a good new DPS to the harness (new DPS hanging in "fresh air"), it should signal to the ECU that there is zero pressure differential which it may be happy with. This might make your testing easier.

 

[bengoa]

Thanks for the detailed post, Anthony489.

I ended up driving to spain with the sensor disconnected, everything worked normally (including cruise control, I didn't try it whith the sensor on). Every 500km I drove for 15 mins at 3500rpms to try to regenerate the DPF passively, since without sensor the ECU wouldn't know that the filter is getting clogged and initiate an active regeneration. I also took the DPF out before leaving and looked clean inside. I'm not an expert but it looked like clean DPF photos from google.

Now my leading hipotesis is that the old sensor is shorted and the new one is the wrong part number (and it's mislabeled in amazon.it). The new sensor has different shape and slightly different diameter in the pipes. The part number is the same according to the seller.

What resistances does the new sensor show, measured both ways round ?

I measured it and only got no electrical connection between all the pins, but I did it before I read your reply and didn't think of measuring it the other way around (It's under the van so hard to access).

In the new sensor it's basically the same resistance both ways, there is 2ohm difference max.

I'm trying to get my hands on a ELM327 that works with multiecuscan and a new sensor, if the third sensor doesn't work either I guess the problem must be in the ECU.

 

[JohnCamper]

UPDATE

So I got the correct MES package, and it arrived on Tuesday (yesterday), and just WOW, what a brilliant tool. I feel like I was working blindfolded, and now I can see what I am doing!
Gendan were fantastic, rapid and helpful responses to my queries, immediate despatch, great product, great service.

The new DPF pressure differential sensor arrived today. Fitted. Plugged into MES. Told the system a new DPF snsor had been fitted.
At first, I did see an issue whereby the sensor showed an open circuit/short fault.
Got underneath, unplugged the sensor, and re-connected it again.
All good.
DPF is not blocked, according to the system now (reading 30% clogged and classed as within normal parameters. All faults gone. Startup idle from cold is fine. All good.
Even cruise Control is functioning normally (presumable because limp mode is no longer being activated by a dodgy sensor signal)

Conclusion:- The DPF sensor was water logged due to extended period of inactivity (condensation etc), causing eventual failure of the sensor, in turn causing DPF clogging mis-diagnosis and limp mode engagement.

Learning points for me:-


Extended periods of inactivity must be avoided.
MES is a "must have".

I want to say a big thanks to all who have guided me towards the solution and fix in what amounted to less than a week from a point of zero knowledge.

 

[bengoa]

So updating my solution, changing the sensor (again) fixed the problem for me too, I've contacted amazon so that they stop selling the wrong sensor with that reference. I've been driving 10 days with the new sensor and it works perfectly.

Thanks to all that helped!