Mysterious Engine Light: Load Calculation Cross Check - Lower Limit Exceeded
- Thread starter Indi
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- 1.4 bby fault code vcds
PlasticMac
Member
Try Group 004, Basic Functions, Block 02. Looks to be the same as Group 061, Block 02.
01, Engine Speed,,Specification (manual): 790...900 RPM | Specification (automatic): 630...730 RPM
02, Voltage Supply,,Specification: 12.0...15.0 V
03, Coolant,Temperature,Specification: 80.0...110.0 °C
04, Intake Air,Temperature,Specification: -30.0...+120.0 °C
Mac.
Just took a look at Group 004 Block 02
I get 11.60v with engine off and 13.80v with engine running.
If I run the engine then switch off the voltage holds up above 12.00v but if I come at it cold then it is showing below 12v.
I think the battery is reasonable as it always starts first time without any hesitation even on cold days.
I get 11.60v with engine off and 13.80v with engine running.
If I run the engine then switch off the voltage holds up above 12.00v but if I come at it cold then it is showing below 12v.
I think the battery is reasonable as it always starts first time without any hesitation even on cold days.
PlasticMac
Member
Battery volts are a bit low, engine off, but seem fine when engine is running. With the engine running, turn the rear screen heater, man, and dipped headlights on, and check Group 004 Block 02 again, to be sure. This is to check the alternator output on load. I think the 61/02 missing voltage reading is not significant, just as Ross-Tech suggested.
Mac.
Could you take a look at Block 32, 33, 34. You’ll have to go for a bit of a drive first to get the values to show. That should help give an indication if there is an air leak or not, and give a general indication of the lambda sensor condition.
Also what brand of sensor did you use to replace your intake manifold pressure sensor?
The missing supply voltage does appear to be a red herring, maybe used on other vehicles as mentioned.
Also what brand of sensor did you use to replace your intake manifold pressure sensor?
The missing supply voltage does appear to be a red herring, maybe used on other vehicles as mentioned.
Indi
Member
The replacement sensor was Febi, so possibly not the highest quality I suppose, for some reason I assumed it wasn’t as critical as say a MAF sensor to use the oem brand though maybe that was a mistake…
I’ll check those blocks if it shows up, but at the moment the light hasn’t turned on for 3-4 days, the most it’s stayed off in weeks, though I’m sure acknowledging that here will make it resurface
Cheers
PlasticMac
Member
That's Groups 32, 33, & 34.
Mac.
Yes groups, I’m not sure where blocks came from.
I wouldn’t be surprised if it turned out the Febi sensor was dud. It’s as critical as the MAF, although it’s probably a bit easier to produce.
The error is saying there is a difference between the expected air flow and the “measured” airflow. That sensor, along with RPM and probably throttle angle, are used to “measure” the air.
It’s worth taking a look at the groups regardless, if you dare to plug it in
. If they show quite extreme values, it may point towards another issue rather than just a slightly off sensor.
I wouldn’t be surprised if it turned out the Febi sensor was dud. It’s as critical as the MAF, although it’s probably a bit easier to produce.
The error is saying there is a difference between the expected air flow and the “measured” airflow. That sensor, along with RPM and probably throttle angle, are used to “measure” the air.
It’s worth taking a look at the groups regardless, if you dare to plug it in
. If they show quite extreme values, it may point towards another issue rather than just a slightly off sensor.
Indi
Member
Lo and behold, the Light came on on my drive home yesterday 
Today I took my laptop and logged the trip, the light appeared about 5 minuets in.
Here is the readings from the end of the trip:
Nothing stood out to me on the log, but I don't really know what I'm looking for, so I'll format and graph the log to post here if its possible there would be useful information.
Today I took my laptop and logged the trip, the light appeared about 5 minuets in.
Here is the readings from the end of the trip:
Nothing stood out to me on the log, but I don't really know what I'm looking for, so I'll format and graph the log to post here if its possible there would be useful information.
PlasticMac
Member
With luck, the graph will show a deviation of at least one of the blocks at the five minute markLo and behold, the Light came on on my drive home yesterday
Today I took my laptop and logged the trip, the light appeared about 5 minuets in.
Here is the readings from the end of the trip:
View attachment 118993
Nothing stood out to me on the log, but I don't really know what I'm looking for, so I'll format and graph the log to post here if its possible there would be useful information.
Mac.
We would need to see the graph to check group 33, but 18% is far too high for group 32. Both values should be as close to 0 and possible in group 32. The limit is +/-10%.
The engine is running lean, so lambda control is having to add fuel to get the mixture correct. It could be not enough fuel (Filter, injectors, pump?) or it could too much air.
I would say it’s more likely too much air based on the error code. Either an actual air leak, or, a faulty sensor is causing the ECU to measure less air than is actually entering the engine.
The engine is running lean, so lambda control is having to add fuel to get the mixture correct. It could be not enough fuel (Filter, injectors, pump?) or it could too much air.
I would say it’s more likely too much air based on the error code. Either an actual air leak, or, a faulty sensor is causing the ECU to measure less air than is actually entering the engine.
PlasticMac
Member
If it's an inlet air leak, it would be a leak after the MAF sensor, I think?
Edit: There is no MAF in the 1.4. Uses inlet temperature and pressure sensors, so look at:
Group 003,0,Basic Functions
Block 03,1,Engine Speed,,Specification (manual): 790...900 RPM
Block 03,2,Intake manifold,pressure,Specification: 240...420 mbar
Block 03,3,Throttle Drive,Angle Sensor 1,for EPC (G187) | Specification: 0.0...11.0 %
Block 03,4,Ignition,Timing Angle,Specification: 0.0...10.0 °BDTC
Group 004,0,Basic Functions
004,1,Engine Speed,,Specification (manual): 790...900 RPM
Block 04,2,Voltage Supply,,Specification: 12.0...15.0 V
Block 04,3,Coolant,Temperature,Specifiation: 80.0...110.0 °C
Block 04,4,Intake Air,Temperature,Specification: -30.0...+120.0 °C
See if they look sensible. Probably check the fuel filter first though.
Mac
Last edited:
Indi
Member
The 1.4 petrol's don't have a MAF sensor, so presumably it would have to be after the manifold pressure/temp sensor, narrowing it down to a bad seal between the manifold and head, or the injector seals perhaps...
This is a zoomed in graph of around the time the light lit up (300-340 seconds ish) Oxygen sensor voltage and dynamic factor use the left hand axis, while the rest use the right.
The dynamic factor starts doing stuff at around the time the light came on, I'll see if it behaves the same on my way home.
Here is the graph for the full trip, showing how the lambda self adaption adjusts.
I also just noticed the 'Marker' feature in VCDS, so I'll be using that to get more accurate time stamps in the future
On the topic of it running lean, I did have an error saying bank 1 senor 1 fuel trim low or something to that effect believe, but somewhere along the way it disappeared and hasn't shown up, that must've been about a year ago now. At the time I believe I assumed it was just one of the low battery voltage gremlins...
I changed the sensor due to a 'manifold pressure sensor implausible correlation' error (alongside the load calculation crosscheck error), which did fix it for several months but has now returned, though the wording is ambiguous as to whether its a symptom or a cause.
PlasticMac
Member
While you have VCDS hooked up, try throttle body adaptation.
Mac.
PlasticMac
Member
Just posted that no MAF, and pressure and temp sensor measuring blocks. Did you fit genuine VAG pressure sensor?The 1.4 petrol's don't have a MAF sensor, so presumably it would have to be after the manifold pressure/temp sensor, narrowing it down to a bad seal between the manifold and head, or the injector seals perhaps...
View attachment 118999
This is a zoomed in graph of around the time the light lit up (300-340 seconds ish) Oxygen sensor voltage and dynamic factor use the left hand axis, while the rest use the right.
The dynamic factor starts doing stuff at around the time the light came on, I'll see if it behaves the same on my way home.
View attachment 119000
Here is the graph for the full trip, showing how the lambda self adaption adjusts.
I also just noticed the 'Marker' feature in VCDS, so I'll be using that to get more accurate time stamps in the future
On the topic of it running lean, I did have an error saying bank 1 senor 1 fuel trim low or something to that effect believe, but somewhere along the way it disappeared and hasn't shown up, that must've been about a year ago now. At the time I believe I assumed it was just one of the low battery voltage gremlins...
I changed the sensor due to a 'manifold pressure sensor implausible correlation' error (alongside the load calculation crosscheck error), which did fix it for several months but has now returned, though the wording makes me think its probably just another symptom of it running lean, rather than a cause perhaps.
Mac.
Indi
Member
I ran throttle body adaption and egr adaption a few months ago, which made the light go away for a week or so...
The temp and pressure readings all looked sensible when I checked them a few weeks ago, pressure at around 1000mbar with the engine off, and dropping to within the 240-420 threshold when idling, though under driving conditions it left the threshold in both directions, I assume this is normal based on speed, engine load and overrun...
This was the graph from part of a previous run monitoring blocks 003, 061 and 062. The light came on around 180 seconds
No, the replacement sensor was Febi, for some reason I had it in my head that the pressure sensors were less finicky than MAFs and therefor wouldn't be as brand sensitive, but I couldn't tell you why I thought so or if this is true...
Cheers
Fuel filter was changed last either last summer or the summer before, can't remember off the top of my head, but definitely not more than a year and a half ago, how do I check it, can I disconnect the engine side and see if fuel flows out due to gravity, or do I need to turn the ignition on so the pump starts up?
The temp and pressure readings all looked sensible when I checked them a few weeks ago, pressure at around 1000mbar with the engine off, and dropping to within the 240-420 threshold when idling, though under driving conditions it left the threshold in both directions, I assume this is normal based on speed, engine load and overrun...
This was the graph from part of a previous run monitoring blocks 003, 061 and 062. The light came on around 180 seconds
No, the replacement sensor was Febi, for some reason I had it in my head that the pressure sensors were less finicky than MAFs and therefor wouldn't be as brand sensitive, but I couldn't tell you why I thought so or if this is true...
Cheers
PlasticMac
Member
It would be good to see a log of inlet pressure readings, (Group 003 Block 02), from another car, to confirm the typical range over a run.
Mac.
Mac.
PlasticMac
Member
Check the inlet pressure ignition on, engine off. I'd expect it to be around zero, logically anyway.
Then go negative,, (vacuum), as the engine starts.
Mac.
Indi
Member
I
It sits around 1000mbar if I recall correctly, which makes sense to me as that’s atmospheric pressure