ECM - ECU temp

[Minimucks]

Can anyone shed any light on what sensor this is relevant to?

I've been having cold start issues with what seems like excess diesel/white smoke and juddering.

No fault codes present and no dash lights. Seems ok once up to 90 temp on the dash.

The ecu temp shows as -265.1 degrees. Presumably this sensor has failed / open circuit? It does change but only to around 250 degrees once warm.

Van is 2019 150psi with 24k.

Thanks in advance for any help!

 

[Dav-Tec]

I'd say that ECU is probably faulty. It should read anywhere near that high or low. Maybe worth looking in the E-Box located under the battery if there's any moisture in there. Would also explain the excessive diesel and poor running

 

[mmi]

What connection profile you are using - there seems to be quite many without a value at all?'
The "raw" values from ECU are just binary digits which need to be scaled to be meaningful for humans.

I would say your -265.1 C should actually read + 8C (= -265.1+273.1) - would that align with ambient temperature?

 

[Minimucks]

What connection profile you are using - there seems to be quite many without a value at all?'
The "raw" values from ECU are just binary digits which need to be scaled to be meaningful for humans.

I would say your -265.1 C should actually read + 8C (= -265.1+273.1) - would that align with ambient temperature?

Thanks,
I'm simply using a carista dongle but with the car scanner app on my phone.

I don't have access to vagcom etc!
Ambient temp was prob between 8-10c at the point of the screenshot.

Engine was not running at time of test and last used two days ago.

 

[mmi]

I'm simply using a carista dongle but with the car scanner app on my phone.

The Carista dongle works just fine. The Car Scanner (at least the paid version) has (under settings) more than 30 connection profiles for VW engines. In the profiles are the scalings for various sensors - but still have to be a bit cautious when seeing "funny" values.

It does change but only to around 250 degrees once warm.

Must assume you mean MINUS 250 degrees - that would equal to +23 C - if my theory - so ECU would be 15 degrees above ambient when warmed up (sounds correct!)

 

[Minimucks]

The Carista dongle works just fine. The Car Scanner (at least the paid version) has (under settings) more than 30 connection profiles for VW engines. In the profiles are the scalings for various sensors - but still have to be a bit cautious when seeing "funny" values.


Must assume you mean MINUS 250 degrees - that would equal to +23 C - if my theory - so ECU would be 15 degrees above ambient when warmed up (sounds correct!)

Thanks,
Yes correct -250c is what I meant. Your theory seems to make sense in my head.

Time to look elsewhere for my issues then?

 

[mmi]

Thanks,
Yes correct -250c is what I meant. Your theory seems to make sense in my head.

That's good. Actually this specific ECU sensor doesn't use the -273.1 scaling (seen in the other value).

Time to look elsewhere for my issues then?

Yes, it would have been too easy.
Failed glow plug would have been a candiadte for white smoke (unburned diesel) as they stay on two minutes after startup. But shouldn't be a problem with only 24kmiles.
VCDS would be very useful tool for further analaysis.

cold start

What's the temperature then?

 

[Minimucks]

That's good. Actually this specific ECU sensor doesn't use the -273.1 scaling (seen in the other value).


Yes, it would have been too easy.
Failed glow plug would have been a candiadte for white smoke (unburned diesel) as they stay on two minutes after startup. But shouldn't be a problem with only 24kmiles.
VCDS would be very useful tool for further analaysis.


What's the temperature then?

Well I say cold start it's just the first start of the day it seems, or at the end of the day 8 hours later.

Temperature is generally above zero. Realistically 5c minimum on average since it's started.

One thing I have noticed is that the battery is on its last legs. It runs at above 14v driving. Sits around 12v pre startup and drops to around 10v cranking.
Is it possible for a low voltage to cause such issues?

 

[mmi]

Is it possible for a low voltage to cause such issues?

Not likely - as the voltage is good as soon as engine is running. Also too low voltage should manifest itself as fault code.
Does the engine fire up immediately, or does it need extended cranking?

 

[Minimucks]

Occasionally an extended cranking.
Maybe 1 in 10 starts.

 

[roadtripper]

That's good. Actually this specific ECU sensor doesn't use the -273.1 scaling (seen in the other value).

As an aside that isn't a scaling factor, that's the offset between Kelvin and Celsius so looks like something is doing an unnecessary units conversion at some point.

A prehistory in physics makes certain numbers leap off the page at me

 

[mmi]

As an aside that isn't a scaling factor, that's the offset between Kelvin and Celsius so looks like something is doing an unnecessary units conversion at some point.

A prehistory in physics makes certain numbers leap off the page at me

Yes, you are right. For this specific value the offset is 0 and the scaling factor is 0.1 thus giving a resolution of 0.1 degrees.
This morning my ECU returned raw data value of "0xFFAE"

Spoiler: Scaled decimal value

-8.2 °C

 

[Minimucks]

Just drove around 80 mike's today and got a fault code appear but still no dash lights.

 

[mmi]

Just drove around 80 mike's today and got a fault code appear but still no dash lights.

View attachment 223628

P20EE (Generic OBD code) = 31103 (VW specific code).

Pending DTCs are fault codes that have been identified by the ECU but are deemed not yet critical enough to trigger the MIL.

 

[Minimucks]

P20EE (Generic OBD code) = 31103 (VW specific code).

Pending DTCs are fault codes that have been identified by the ECU but are deemed not yet critical enough to trigger the MIL.

I'm gettin the van looked at later this week but thought I'd take another poke around the sensors earlier on.

It seems as soon as the engine hits 90/91 degrees it runs normal, or as good as!

This seems to coincide with the Nox sensor kicking in from 65535 ppm down to 4 ppm. (Presumably working as it should)?

The other thing that seems strange is the cold temp reading of the exhaust gas temperature bank 1 sensor 1 shows as 75 degrees.
( Increases to 216.5 degrees after a short drive at full temperature).

Screenshots attached of completely cold engine, warmed up on Tickover and hot after short drive.

Any thoughts? @mmi

 

[roadtripper]

Screenshots attached of completely cold engine, warmed up on Rickover and hot after short drive.

Is Rickover when the engine sounds like it's Never Gonna Give You Up?

 

[Minimucks]

Is Rickover when the engine sounds like it's Never Gonna Give You Up?

But it feels like it's gonna let me down

 

[mmi]

This seems to coincide with the Nox sensor kicking in from 65535 ppm down to 4 ppm. (Presumably working as it should)?

Yes - NOx-sensor indeed wakes up when things have warmed up. However, the raw data the sensor reports is plain 0 till sensor activation. Perhaps the 65535 (=FFFF) is a way to report "not ready" status - thus combined status and actual measument into a single value.

The other thing that seems strange is the cold temp reading of the exhaust gas temperature bank 1 sensor 1 shows as 75 degrees.
( Increases to 216.5 degrees after a short drive at full temperature).

Is the reading always the same 75 when cold - if so it possibly would be just an interpretation (of Car Scanner), or depending from which "address" Car Scanner is getting it's data - there are several sources for the data - e.g. actual, filtered and even just calculated numbers.

The sensor itself is capable of much lower numbers as per raw data below


All the above could be related to which Car Scanner connection profile you are using - as Car Scanner seems to try to read data even from some non-existing (on this engine) sensors.