DPF regeneration & power loss

[Lee540]

Hi all. Still trying to get to the bottom of this problem where I lose power every now and then. It’s not done it for 3 months but just started again in the last 2-3 days.
Few points I need advice on:

- My diagnostics tells me I have a low voltage somewhere but won’t tell me where.
- Drove to work the other day and everything was perfect even the engine management light went out. However it came back on during the drive home (on start up).
- Drove to work the next day, engine lost power so got someone to read and record live data (see photos).

Couple of things I noticed:
- The coolant temp between 1 and 2 is different. Was wondering shouldn’t this be the same or even close?
- The voltage of the oxygen sensor is different on one to the other. Could this be my low voltage issue?
- It’s also telling me that it’s never completed a DPF Regen. That doesn’t sound normal.

Any comments or advice would be gratefully received.

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Maybe your scanner doesnt have the necessary interface to read DPF data.

Do you notice power loss throughout all gears? Do you know when your van is doing a regen? i.e faster idle, high engine oil temp, fans running.. when the revs drop back down to 800rpm, is it normal to drive again?

 

[pmblue57]

Not thought of that. However I use know when it had just done a regen as the fan was on full when I stopped. Use to happen regularly but not seen it for about 6 months now. Coupled with the fact the auto start/stop feature doesn’t work every time I’m thinking there must be something that’s common to both that’s draining power causing ‘low voltage’ fault.
Is there a list of all the functions used for regen and a list for auto start/stop? I.e they both use the wheel speed sensors …..

 

[mmi]

My diagnostics tells me I have a low voltage somewhere but won’t tell me where.

I'm not sure if I understand - do you mean code P0562 mentioned in

P0562 Low Voltage

What is regarded as low voltage for T6? Would 11.7v at the battery not running trigger the P0562 fault code?

www.t6forum.com

or something else? The code P0562 just indicates "system voltage too low", thus a weak battery, failing altenator, poor connection, etc.
Can you see timestamp when the fault was captured - to identify if it coincidewith power loss, or a separate issue?

The coolant temp between 1 and 2 is different. Was wondering shouldn’t this be the same or even close?

Presumably the lower temperature is radiator outlet temperature - what was temperature outside then - less than 24 °C I hope?

The voltage of the oxygen sensor is different on one to the other. Could this be my low voltage issue?

Not likely.

It’s also telling me that it’s never completed a DPF Regen. That doesn’t sound normal.

I don't see that in your data unless you meant these


I have never seen any activity on those - they have always been plain zeros.

Anyways, would be useful to know what engine (engine code, what year, mileage, etc.

 

[pmblue57]

The van is a 69 reg 2.0 tdi T32. It’s done 80,000 miles, was remapped when I bought it, EGR valve removed and AdBlue removed.
The ambient temperature was low as it was in the morning about 12 degs.
The code P0562 has been there right from the start, when the loss of power started about 4-5 months ago.

 

[pmblue57]

I'm not sure if I understand - do you mean code P0562 mentioned in

P0562 Low Voltage

What is regarded as low voltage for T6? Would 11.7v at the battery not running trigger the P0562 fault code?

www.t6forum.com

or something else? The code P0562 just indicates "system voltage too low", thus a weak battery, failing altenator, poor connection, etc.
Can you see timestamp when the fault was captured - to identify if it coincidewith power loss, or a separate issue?


Presumably the lower temperature is radiator outlet temperature - what was temperature outside then - less than 24 °C I hope?

Not likely.


I don't see that in your data unless you meant these
View attachment 248382

I have never seen any activity on those - they have always been plain zeros.

Anyways, would be useful to know what engine (engine code, what year, mileage, etc.

Same code.

I did think the code meant faulty battery but I’m recording 14+v during running so can’t be that. Now I’m thinking it’s a voltage drain on a sensor, etc.

I can delete the code but it comes back the next day. Maybe the fault is intermittent ¯\_(ツ)_/¯

 

[mmi]

Now I’m thinking it’s a voltage drain on a sensor, etc.

Not sure about that. The sensors have their own stabilized 5 Volts supplies. Voltage glitches with them should be captured by fault codes stating "Sensor Reference Voltage..."

I’m recording 14+v during running

Have you checked fuses supplying ECU.
Is the voltage permanently 14+, no dips at all?

Does your scanner have so called freeze frame data about the faults? Would be helpful to know when the fault was captured - the most "natural" moment would be at engine start up. Could you read fault codes right after engine start - if none then read again at the end of journey (after power loss) engine still running?

 

[pmblue57]

What would happen if the 5v supply line was damaged on a sensor that was used to trigger the DPF regen? Do you think this is viable?
My diagnostics has a function where I can read battery voltage real time on a graph. Although I never see it drop below 14v I’ve never done it on start up or when the fault code appears?
You thinking it’s the battery?

 

[mmi]

What would happen if the 5v supply line was damaged on a sensor that was used to trigger the DPF regen? Do you think this is viable?

I'm confident that would trigger a fault code or two. Also the DPF regen is triggered off calculated value - well, certainly it's more or less based on sensor values.

Although I never see it drop below 14v

Well, I would expect it to drop at some point down to 13.4V, or even lower because the battery management should eventually register fully charged state and ease charging a bit. Unless the battery is about to expire. But still, the alternator during running can keep even poor battery up to perfect voltage - so a bit difficult to see low voltage happening when engine is running.

I'm just trying to pinpoint when the "low voltage" happens - just to rule it in or out as the culprit

What's your engine code - on sticker under dash by steering column. The live data screenshots you posted makes me think it's EU5 engine (=without AdBlue)

 

[pmblue57]

You’re right the voltage does vary from start up, early running to end of a trip. I think I did mention on an early post that the non running voltage is below 12v and suggest I should change the battery. However I’d convinced myself 14v when running there wasn’t a problem with it.
The van is a Euro6, the AdBlue was removed.
About 6 months ago the engine management light came on. The fault was a faulty glow plug on #4. Then a few weeks later the engine started to lose power. I had the glow plug replaced hoping that would fix the power lose problem. Picked up the van the engine management light was out. Next day on start up the light was back on. Read the fault code and it was a fuel temperature sensor. Replaced that, light was out for a day, next morning it was back on. Now the current fault is a low voltage.
On a positive note the light went out for the first time on its own the other week when I started up to go to work. Van ran great, however no sign of regen or auto start/stop. Unfortunately light came back on when started up to come home from work in the afternoon.

 

[DaveD]

- It’s also telling me that it’s never completed a DPF Regen. That doesn’t sound normal.

The van is a 69 reg 2.0 tdi T32. It’s done 80,000 miles, was remapped when I bought it, EGR valve removed and AdBlue removed.

I don't pretend to be an expert but if the van has had the AdBlue mapped out then you can't expect diagnostics to show data on regens.

 

[pmblue57]

This is what’s worrying me. I spoke to the guy who removed the AdBlue and EGR and asked what are the side effects. He’s says his not seen any and not had problems like this before. ¯\_(ツ)_/¯

 

[dane]

If it was me, I would be checking the wiring in the engine bay for any obvious signs of damage cables specially round the area of the fuel temp sensor.

Cables can get damaged or break. That causes high resistance which then could result in a voltage drop or short to ground which doesn’t alway blow a fuse.


Also faulty cabling won’t necessarily cause a noticeable issue if the conductors are just touching, it’ll just lay in wait. It’s possible the mechanic working on the vehicle moved a wire which disturbed the fault?

If nothing obvious, and it’s challenging, get a wiring diagram and multi meter you could test the continuity of the wires.

 

[pmblue57]

So tempted to change the battery but In the back of my mind I know it’s not going to solve the problem.
A wiring fault makes more sense and I did start to check all the wires but soon discovered it could be a corroded pin and I would never know just by looking unless I took the pin out of the socket.
The resistance test seems the way to go but even then I’d have to lucky the wire is sitting in the right position.
Like you say I’ll start with the fuel temp area.

 

[Lee540]

Has anyone checked your fuel pump or injectors?

 

[pmblue57]

Hi! Not that I know of.

I did start to look at the connectors over the weekend. I started cleaning one at a time to see if the engine management light went out. Got to the third connector and the light went out. ¯\_(ツ)_/¯ Lucky!

However not sure if it’s fixed the engine power lose yet.

I started to think back on what I did over the passed 6 months and I remember jet washing the engine bay. Maybe that wasn’t a good idea!

 

[Lee540]

Do you know what plug it was?

Have you checked DPF pressure sensor as well? So many sensors!!!

 

[pmblue57]

It was the first three plugs (see picture) you can see when you lift the bonnet, in the middle under the bulkhead. Not sure which one it was now but the engine management light came back on the journey home so I’ll have a better look at the weekend.