For the experts: Live diagnostic data

[breeze]

I've been wondering if there is a problem with the fuel economy of my 2008 C320 CDI pretty much since I have bought it.

http://forums.mercedesclub.org.uk/showthread.php?t=117989

I've spoken to the dealer who tells me that a best of 32 MPG from a tank on mostly motorway is within acceptable limits (which surprises me...) so have decided to take a different tack, this time with a fault code reader.

The reader that I went with was an e-Bay Autel MS509. I understand that this is not genuine, but it seems to work fine.

The car is showing no fault codes.

Live data shows the following at idle after warming up the car:
DTC_CNT 0
LOAD_PCT(%) 27.1
ETC(deg F) 189
MAP (inHg) 29.8
RPM (/min) 603
VSS (MPH) 0
IAT (deg F) 73
MAF (lb/min) 1.892
TP (%) 31.4
O2S B1S1---B2S----
OBD EOBD
RUNTM (sec) 1124
MIL_DIST (mile) 0
FRP (PSI) 3480.9
EQ_RATB1S1 1.999
O2B1S1 (v) 0.886
EGR_PTC (%) 4.7
EGR_ERR (%) 21.2
FLI (%) 32.3
WARM_UPS 255
CLR_DIST (mile) 3299
BARO (inHg) 29.2
CATEMP11 (deg F) 321.98
CATEMP12 (deg F) 2192.0
VPWR (v) 13.760
AAT (deg F) 61
APP_D (%) 6.3
APP_E (%) 3.1
TAC_PCT (%) 74.9
MIL_TIME 0h:00m

Does this look OK? I was hoping to be able to catch a high fuel trim reading, or similar, but it doesn't seem like any of the above cover that.

 

[S.Speed]

I don't know about live data but I DO know what both the E320 Cdi's achieved on motorway runs...
Being VERY realistic I always get around 40mpg on a long run... That figure is without watching the fuel gauge at all..
Also being realistic I get 32mpg around town..
Last Sunday I went to Portmeirion and back with 2 adult passengers (364 miles) and it averaged 40.1mpg
My motorway speeds are 70 - 80.
So in view of the C class being a lighter car, I too would not be happy with the figures you have given..
BUT . . .
What sort of speeds are you doing?
If I boot mine on the odd occasion I feel the need then I certainly wont be getting 40 mpg !!!

 

[mattuk]

Well. Best would be C instead of F in temp as metric instead of imperial.

I can't see short and long fuel trims. Maybe diesel doesn't show.
One read isn't accurate. You need to get frame data freeze with several reads in some time.
What is wierd for me that TB(throttle body)angle %. It shows 31. That's a lot. On idle should be no more than 10%.

Re-read values once again.do read while engine cold and hot

 

[Miffy]

using 27% of available torque at idle ?

LOAD_PCT(%) 27.1

 

[S.Speed]

I have a autel scanner..
I will scan my car on Wednesday which will be the next time its started.
I know it does live data. If I work out how to save it and post on here then I will do.
You can compare figures in that case.

 

[Miffy]

really these codes should be read out from STAR as a generic odbii scanner is going to leave a lot of holes in the data that will introduce guesswork.

 

[alexanderfoti]

Also, things like load pct are calculated by the ECU, and arent hugely accurate.

Also fuel trim etc, is only for petrol via OBD, to look at fuel trim values on the diesel you need star.

 

[S.Speed]

Depending on whether your reader is genuine or not you may find the options are different or missing. QUOTE]

My Autel is genuine...
Its a Maxidiag EU702
So there you have it..

 

[Benzworx]

I've been wondering if there is a problem with the fuel economy of my 2008 C320 CDI pretty much since I have bought it.

http://forums.mercedesclub.org.uk/showthread.php?t=117989

I've spoken to the dealer who tells me that a best of 32 MPG from a tank on mostly motorway is within acceptable limits (which surprises me...) so have decided to take a different tack, this time with a fault code reader.

The reader that I went with was an e-Bay Autel MS509. I understand that this is not genuine, but it seems to work fine.

The car is showing no fault codes.
Live data shows the following at idle after warming up the car:
DTC_CNT 0
LOAD_PCT(%) 27.1
ETC(deg F) 189
MAP (inHg) 29.8
RPM (/min) 603
VSS (MPH) 0
IAT (deg F) 73
MAF (lb/min) 1.892
TP (%) 31.4
O2S B1S1---B2S----
OBD EOBD
RUNTM (sec) 1124
MIL_DIST (mile) 0
FRP (PSI) 3480.9
EQ_RATB1S1 1.999
O2B1S1 (v) 0.886
EGR_PTC (%) 4.7
EGR_ERR (%) 21.2
FLI (%) 32.3
WARM_UPS 255
CLR_DIST (mile) 3299
BARO (inHg) 29.2
CATEMP11 (deg F) 321.98
CATEMP12 (deg F) 2192.0
VPWR (v) 13.760
AAT (deg F) 61
APP_D (%) 6.3
APP_E (%) 3.1
TAC_PCT (%) 74.9
MIL_TIME 0h:00m

Does this look OK? I was hoping to be able to catch a high fuel trim reading, or similar, but it doesn't seem like any of the above cover that.

Sorry but if you are happy with your code reader then why are you asking this ?

 

[Benzworx]

Get it put on star then you will know

 

[breeze]

I don't know about live data but I DO know what both the E320 Cdi's achieved on motorway runs...
Being VERY realistic I always get around 40mpg on a long run... That figure is without watching the fuel gauge at all..
Also being realistic I get 32mpg around town..
Last Sunday I went to Portmeirion and back with 2 adult passengers (364 miles) and it averaged 40.1mpg
My motorway speeds are 70 - 80.
So in view of the C class being a lighter car, I too would not be happy with the figures you have given..
BUT . . .
What sort of speeds are you doing?
If I boot mine on the odd occasion I feel the need then I certainly wont be getting 40 mpg !!!

Perfectly normal speeds. If I sit at 60 MPH on the motorway I might get the instant read out to approach 40 MPG but that soon disappears. As my earlier thread I could get 40 MPG from a tank on my last car (W203 C270 CDI) easily and that had been known to touch 50 MPG over long distances.

I am checking brim to brim, incidentally, and the fuel computer is accurate.

 

[breeze]

using 27% of available torque at idle ?

LOAD_PCT(%) 27.1

Perhaps as a diesel that isn't so unrealistic...?

 

[breeze]

I have a autel scanner..
I will scan my car on Wednesday which will be the next time its started.
I know it does live data. If I work out how to save it and post on here then I will do.
You can compare figures in that case.

Please do!

 

[breeze]

Depending on whether your reader is genuine or not you may find the options are different or missing. You need to create a custom file with the right PID's that you wish to monitor. Look at the options in Live data menu for something along those line's, then select the one's you wish to monitor. Keep them to a minimum as only so much data can be read via the ODB port at anyone time ( try to keep them below 6 but ideally 3 ir 4). You need to also understand which of the PID's are genuine vs calculated if you look at your list you have both a map and maf reading.

On the subject of fuel consumption have you verified the displayed average is accurate by recording actual mileage vs amount of fuel you put in at the pump its not unheard of for the displayed consumption to be wrong.

I did try selecting a few at random and the values did not change. To be honest I'm not sure what I should be looking at; Fuel Trim was what I was hoping to find and it doesn't show it.

 

[breeze]

Sorry but if you are happy with your code reader then why are you asking this ?

As far as I can tell the code reader is working.

My question is how to interpret the data.

 

[breeze]

I am leaning towards STAR but I must say that my experience to date with main dealers has been mixed at best.

I bought the car from Derby and had a truly nasty experience. Later I spoke to Watford who were much better, but the technician there said that a best of 32 MPG from a tank was good - that doesn't quite tally with posts here and conversations that I have had with another C320 owner.

That said, fuel trims would be good. Hmm...

 

[S.Speed]

My Live Data for comparrison

My own data in RED.. 2007 E320 Cdi with 43k miles

My MAF reading is massively different to yours !!

DTC_CNT 0 0

LOAD_PCT(%) 27.1 23.1

ETC(deg F) 189 88

MAP (inHg) 29.8 29.5

RPM (/min) 603 700

VSS (MPH) 0 0

IAT (deg F) 73 75.2

MAF (lb/min) 1.892 0.03

O2S B1S1---B2S----

OBD EOBD

RUNTM (sec) 1124 1609

MIL_DIST (mile) 0 0

FRP (PSI) 3480.9 3886.3

EQ_RATB1S1 1.999 1.999

O2B1S1 (v) 0.886 1.799

WARM_UPS 255 17

CLR_DIST (mile) 3299 2139

BARO (inHg) 29.2 29.5

CATEMP11 (deg F) 321.98 648

VPWR (v) 13.760 14.2

 

[breeze]

Thanks for this - it is really good.

A few obviously stand out:
ETC
O2B1S1
CATEMP11
MAF

Could the MAF be yours reading voltage? A quick Google suggests the value of mine is reasonable.

 

[turbopete]

Thanks for this - it is really good.

A few obviously stand out:
ETC
O2B1S1
CATEMP11
MAF

Could the MAF be yours reading voltage? A quick Google suggests the value of mine is reasonable.

i suspect Simons etc reading is in C not F as yours is.
catemp, i presume is the temp inside the cats? if so then it has just been running differently to yours (possibly driven to warm up rather than idling etc)

the MAF reading, i cant comment on. Simon may have the EGR deleted on his car. im sure he will let us know 1 way or the other!

 

[S.Speed]

MAF reading was(lb/min).. Whatever that is !
No I haven't had the EGR delete done as there is no way to do this on the V6 using the shunt method.. Apparently GAD tuning can delete it via reprogramming the ECU though.
My readings were in Degrees C but I converted them (online to Degrees F) to match the OP's..

As someone once said.. "Hope this helps"