Mysterious Engine Light: Load Calculation Cross Check - Lower Limit Exceeded

Indi

Indi

Member
I have been hunting this engine light on and off for months now and have come back with nothing.

A year or two ago I had a load of fault codes, (including the one mentioned as far as I remember) these were mainly electrical and mostly fixed by a new alternator and eventually a new battery too. The car was sat unused for a few terms while I was at university, and a missing bonnet drain cup meant water was being funneled onto the alternator. This fixed most of the issues, except a code for the EGR valve which I replaced solving the issue.

There was then a clear patch with only occasional intermittent codes (I cant really remember, but possibly EGR valve and Intake manifold pressure sensor) and stretches of no engine light in between.

Then 6 months ago maybe started getting codes for the manifold pressure sensor and load calculation cross check more and more frequently.

17550 - Load Calculation Cross Check
P1142 - 35-10 - Lower Limit Exceeded - Intermittent
17961 - Barometric / Manifold Pressure Signals
P1553 - 35-10 - Implausible Correlation - Intermittent



The obvious suspect was the manifold combined pressure/temp sensor, as this is used instead of a MAF in the 1.4 MPI so would explain both codes. However replacing it didn't fix the Load Calculation Cross Check code, though it did seem to get rid of the Manifold Pressure code.


On the Ross Tech Website it lists the following:

17550/P1142/004418 - Load Calculation Cross Check: Lower Limit Exceeded​

Possible Causes​

  • Mass Air Flow Sensors (G70) faulty
  • Intake Air System faulty/leaking (false Air)
  • Throttle Pedal faulty
  • Throttle Body dirty/faulty

Possible Solutions​

  • Check Mass Air Flow Sensors (G70)
  • Check Intake Air System
  • Check Throttle Pedal
    • Check Throttle Pedal Position Sensor (G79)
    • Check Throttle Pedal Position Sensor 2 (G185)
  • Check Throttle Body
    • Check Angle Sensor 1 for Throttle Actuator (G187)
    • Check Angle Sensor 2 for Throttle Actuator (G188)
  • Check Engine Control Unit

As I said earlier, there is no MAF, but G70 refers to the Manifold pressure sensor on the 1.4 MPI, which I had already replaced.

I had poked around with the intake system a year or two ago when I did the alternator, and noticed a mouse had chewed the rubber off the flap that switches between the hot and cold intakes, It was not available new or aftermarket anywhere I could find, and the second hand one I got was in worse shape than the original, so just put it back together as is. This is all upstream of the G70 sensor so as far as I can tell should not be causing the errors I have.

I decided to double check the air intake system and change the air filter, and found the mouse damage was more extensive than I had realised:

1704799851349.jpeg


Changing the filter didn't help and the light came back after a day or two.

Next I decided the throttle body and EGR adaption, as I did not do this when changing the EGR valve as I didn't have VCDS at the time.
Without resetting the codes, the light disappeared for a almost a week, (using the car twice a day for about 12 miles) the longest it had stayed off in a long time, however after the brief interlude returned to lighting up every trip. The EGR code has not showed up again since.

I checked the four other sensors listed, but only one seems present on the 1.4 (G79 iirc) and it seemed to go through a range of values as I pressed the pedal, though I didn't probe any further than that.

Over the weekend I drove about 750 miles over 4 trips, and at the end of trip 3 the ABS warning beeped at me and all the associated lights came on on the dash, But the brakes were fine, instead just telling me to check the engine DTCs:

01314 - Engine Control Module
013 - Check DTC Memory - Intermittent

The engine module showed

17550 - Load Calculation Cross Check
P1142 - 35-10 - Lower Limit Exceeded - Intermittent
17961 - Barometric / Manifold Pressure Signals
P1553 - 35-10 - Implausible Correlation - Intermittent

Which was the first time the manifold pressure code had showed up in the several months since I'd changed the sensor.

I did not reset the codes, but the brake lights went away when I turned off the car, though it did come on again once.


Further info;
The car is a 1.4 Petrol BBY, 115k miles, still drives fine, I don't notice any difference in power or economy, returned 55mpg @ 55mph over the weekend. I run it on E5.
A month or two ago I tried logging some trips with VCDS to try to catch the error and associated sensor graphs as it happened, but over the two trips the light conveniently did not show up.
I had been driving the car for over a year with the filter in that state, and miraculously seems to have suffered no consequences (unless this is somehow related) I presume it was all soft mouse nest materials so just got burned off without causing too much damage.

Thanks for reading, I have reached a bit of a wall so thought I'd see if anyone else had any ideas.

Cheers,
Indi
 
Running a car for quite a long time effectively without an air filter will cause any sensors that are in the intake to get contaminated. I would check/test/replace all sensors in the intake. I'm not an expert on petrols but I'd be surprised if it doesn't have an air mass meter, perhaps someone else can confirm. If it has then that is your favorite as they can be very sensitive to contamination.

T
 
As the sensors in the airstream are after the filter there is a good chance they are contaminated and need careful cleaning / replacing. As you have been attacked by Stuart Little there is a high chance further wiring damage has not been noticed yet. So check all the wiring looms in the engine bay including where the cables pass into the cabin. Repair all damage found.

Get a cat!!!!
 
audifan said:
As the sensors in the airstream are after the filter there is a good chance they are contaminated and need careful cleaning / replacing. As you have been attacked by Stuart Little there is a high chance further wiring damage has not been noticed yet. So check all the wiring looms in the engine bay including where the cables pass into the cabin. Repair all damage found.

Get a cat!!!!
Click to expand...
All the looms look good, there is one of the rubber sleeves that has been chewed but the insulation of all the wires inside hasn't been touched, and its not a part of the loom relevant to this anyway (above the drivers side suspension strut, so headlight, and brake fluid sensor)
The loom from the pressure sensor hasn't been touched, I followed it back until it goes into a hard plastic pipe and disappears back under the bulkhead.

I have had another look but still the only sensor I can find in the airflow is the combined manifold temp and pressure sender, which I have already replaced.

I am going to double check that the connector plug is clean and making good contact, and then see if I can trigger the light by wobbling the wires where they go into the plug... that would be a delightfully easy fix

Then I guess its onto the diagnostic test procedure for the throttle body...
 
I have the same model and same issue of that error code popping up and the random frequency sounds just like yours.

17550 - Load Calculation Cross Check
P1142 - 35-10 - Lower Limit Exceeded - Intermittent

I have done all the suggestions from Ross Tech but still the same code will come up. Like you, the engine runs fine with no change when the light comes on.

For me both the EPC and yellow check engine light come on together. Then when I turn off the ignition and back on again the EPC light goes out but the yellow check engine light stays on. It starts and drives fine. When I check the module on VCDS its always the same 17550 code and it clears no problem. Its been doing this for a good few months and I clear the code and carry on.

The last two times though it's done something weird. Both lights come on, I stop at some point and start again and just the check engine light is on as normal but then after a distance of a few miles the check engine light goes out on its own! I did not know it could even do that? Please comment if you can confirm if the light can go out once it is triggered.
Later, with no warning lights on the dash if I check VCDS then the 17550 code is there and I clear it.

The first time it self cleared I noticed the light went out just after I had put a full tank of fuel in so I thought this may be something to do with it - flap release switch, fuel sender or cap blocked so when it happened again the next day about 10 miles later I thought I would open the fuel tank and replace the cap but it did not clear the light. It did clear itself a few miles later though.

As I said, I have done all the suggested things - cleaned the EGR, cleaned the throttle body and aligned, checked air filter, and checked pipes, new mass airflow sensor and checked plugs and wires, even pulled out the throttle pedal and cleaned that (it was clean though and in good condition for 83,000 miles so I think they are pretty reliable).

I do think it is something minor and I am OK driving with the light on but I'd like to fix it so that the warning light can do it's job for any other problem.

Any thoughts anyone?
 
When you scan, are you doing a full scan of all controllers, or, just the engine?
There are conditions in other, (typically ESP, Air Bag, ABS, etc), controllers, which are considered a safety risk, and will trigger Limp Home Mode in the ECU, and so display the EML. If that non engine condition clears, so will the EML.
By EPC light, I'm guessing you mean ESP, (stability), warning?
Mac.
 
PlasticMac said:
When you scan, are you doing a full scan of all controllers, or, just the engine?
There are conditions in other, (typically ESP, Air Bag, ABS, etc), controllers, which are considered a safety risk, and will trigger Limp Home Mode in the ECU, and so display the EML. If that non engine condition clears, so will the EML.
By EPC light, I'm guessing you mean ESP, (stability), warning?
Mac.
Click to expand...
He means the Electronic Power Control light, it’s the indicator for faults in the computer controlled engine systems

I’ve been doing full scans for mine and other than a few minor electrical faults (radio, air con, etc) it’s just the load calculation cross check and manifold pressure codes

NeilA2 said:
I have the same model and same issue of that error code popping up and the random frequency sounds just like yours.

17550 - Load Calculation Cross Check
P1142 - 35-10 - Lower Limit Exceeded - Intermittent

I have done all the suggestions from Ross Tech but still the same code will come up. Like you, the engine runs fine with no change when the light comes on.

For me both the EPC and yellow check engine light come on together. Then when I turn off the ignition and back on again the EPC light goes out but the yellow check engine light stays on. It starts and drives fine. When I check the module on VCDS its always the same 17550 code and it clears no problem. Its been doing this for a good few months and I clear the code and carry on.

The last two times though it's done something weird. Both lights come on, I stop at some point and start again and just the check engine light is on as normal but then after a distance of a few miles the check engine light goes out on its own! I did not know it could even do that? Please comment if you can confirm if the light can go out once it is triggered.
Later, with no warning lights on the dash if I check VCDS then the 17550 code is there and I clear it.

The first time it self cleared I noticed the light went out just after I had put a full tank of fuel in so I thought this may be something to do with it - flap release switch, fuel sender or cap blocked so when it happened again the next day about 10 miles later I thought I would open the fuel tank and replace the cap but it did not clear the light. It did clear itself a few miles later though.

As I said, I have done all the suggested things - cleaned the EGR, cleaned the throttle body and aligned, checked air filter, and checked pipes, new mass airflow sensor and checked plugs and wires, even pulled out the throttle pedal and cleaned that (it was clean though and in good condition for 83,000 miles so I think they are pretty reliable).

I do think it is something minor and I am OK driving with the light on but I'd like to fix it so that the warning light can do it's job for any other problem.

Any thoughts anyone?
Click to expand...
Sounds exactly the same as mine, EPC and emission control/engine management light both coming on together. The EPC light occasionally goes away by itself during a trip though always disappears when I turn on the engine. The engine management light goes away if the car doesn’t detect the fault for a while (3 clear trips possibly?)

I’m continuing to drive with mine at the moment (same for the last 4 months or so) It’s got more and more frequent, now triggering pretty much every trip, though it still drives fine.
There’s occasionally very slight rev hunting or lurching, but very minor so I think probably just me looking for correlations
 
Hello,
It's lucky the code doesn't seem to have any negative effect on the cars performance and fuel miles.
I did a quick Internet search and I came up with 'unexpected air' can cause an error.
Your did the throttle body adaption. (AFAIK)The MAP on the side of the air intake manifold measures the air pressure inside that part. I guess the ECU looks at the throttle pedal position adjusts the butterfly in the throttle body to meter the air. The ECU checks the temperature of the air and engine coolant reads the pressure inside the intake manifold and meters the fuel sent to the injectors.
ECU will monitor the 2 lambda sensors to see that the combustion is clean.

Your car seems to be doing these tasks very well indeed as your fuel miles are good.
I'm going to reel off a big boring list of possible air leaks that may or may not be throwing the engine fault code. Forgive my ignorance but I've owned 2 AUA engines so there are subtly differences in your engine systems.
My thoughts on the air mismatch are.
Engine crank case breather seal/gasket and hose check
Injector o ring seals
Air intake manifold seal/gasketsx4
Egr metal gasket seals both ends of pipe
Throttle body metal and rubber gasket seals
Hose and one way valve seal on brake booster

Fuel tank cap not venting properly or seal perished
Engine oil filler cap seals x2 one in service flap and 1 on rocker cover
Map sensor o-ring seal

A quick look at 7zap for the intake of a BBY I forgot the charcoal canister hose and can't see the brake boost hose in the diagram.

All the best with traking this gremlin

EDITS....
7zap crank case breathers

Going on a hunch how new is the brake light switch?
EDIT 2...
Forgot there are a o-rings on the cam sensor, oil filler pipe and dip stick tube which are nothing to do with combustion process but the AUA engine disliked a vacuum leak I guess the BBY is similar.
 
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I hear that this valve (from the intake diagram) can be troublesome.
1000000332.jpg


EDIT

If you have your intake intake manifold off the car at some point. It would be peace of mind to check seal number 8 is OK.

1000000333.jpg
 
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rotifer said:
Hello,
It's lucky the code doesn't seem to have any negative effect on the cars performance and fuel miles.
I did a quick Internet search and I came up with 'unexpected air' can cause an error.
Your did the throttle body adaption. (AFAIK)The MAP on the side of the air intake manifold measures the air pressure inside that part. I guess the ECU looks at the throttle pedal position adjusts the butterfly in the throttle body to meter the air. The ECU checks the temperature of the air and engine coolant reads the pressure inside the intake manifold and meters the fuel sent to the injectors.
ECU will monitor the 2 lambda sensors to see that the combustion is clean.

Your car seems to be doing these tasks very well indeed as your fuel miles are good.
I'm going to reel off a big boring list of possible air leaks that may or may not be throwing the engine fault code. Forgive my ignorance but I've owned 2 AUA engines so there are subtly differences in your engine systems.
My thoughts on the air mismatch are.
Engine crank case breather seal/gasket and hose check
Injector o ring seals
Air intake manifold seal/gasketsx4
Egr metal gasket seals both ends of pipe
Throttle body metal and rubber gasket seals
Hose and one way valve seal on brake booster

Fuel tank cap not venting properly or seal perished
Engine oil filler cap seals x2 one in service flap and 1 on rocker cover
Map sensor o-ring seal

A quick look at 7zap for the intake of a BBY I forgot the charcoal canister hose and can't see the brake boost hose in the diagram.

All the best with traking this gremlin

EDITS....
7zap crank case breathers

Going on a hunch how new is the brake light switch?
EDIT 2...
Forgot there are a o-rings on the cam sensor, oil filler pipe and dip stick tube which are nothing to do with combustion process but the AUA engine disliked a vacuum leak I guess the BBY is similar.
Click to expand...

Cheers, lots to try there, probably be a few weeks till I get a chance to have another crack at it (I’m currently in the middle of a few jobs on the FSI and then the 1.4 is in desperate need of it’s new clutch which arrived yesterday)

But when I get a chance I’ll start systematically replacing some of the seals and O-rings you’ve mentioned

I also have a few VCDS logs covering trips where the light came on so I need to have a look at that and see if there’s any clues,

presumably a sensor briefly flicking to min or max reading before the error shows would indicate an intermittent bad connection or short,
or if the error is preceded by a particularly low intake pressure then that could indicate it opening a seal and sucking in air through one of the places you mentioned…

Thanks
 
I believe that the EPC light is an indication that the ECU has put the engine into Limp Mode, but not, necessarily due to an engine fault.
If the EML goes out, with no Engine DTCs logged, then the ECU is, probably, responding to an instruction from another controller, requesting Limp Mode.
Mac.
 
Hi Mac,
Could it be the brake light switch?
Edit
There very cheap and easy to replace...
 
Hi,

This chap on YouTube has not removed his lower trim properly but the video gives a view of the location.
Edit...
I second that Mac, don't buy a cheap one
 
Hi Mac, it definitely is the EPC light I am talking about.
I just ran a full scan with VCDS and got the following report-
VCDS-Lite
Windows Based VAG/VAS Emulator
Version: Release 1.2
www.Ross-Tech.com
Workshop Code: 000 00000
Self-Diagnosis Log
Wednesday, 24 January 2024, 10:12:48:39051
VIN Number: WAUZZZ8Z43N013861 License Plate:
Mileage: Repair Order:
Chassis Type: 8Z - Audi A2
Scan: 01,02,03,08,15,16,17,18,37,45,46,56,57,75,76,77
------------------------------------------------------------------------------- Address 01: Engine Labels: 036-906-034-APE.LBL
Controller: 036 906 034 CA
Component: MARELLI 4MV 4637
Coding: 00051
Shop #: WSC 02138
VCID: 53D964C4B2ED
WAUZZZ8Z43N013861 AUZ7Z0B2181086
1 Fault Found:
17550 - Load Calculation Cross Check: Lower Limit Exceeded
P1142 - 35-10 - - - Intermittent
Readiness: 0010 0101
------------------------------------------------------------------------------- Address 08: Auto HVAC Labels: None
Controller: 8Z0 820 043 D
VCID: 370130540655
Note: Excessive Comm Errors

------------------------------------------------------------------------------- Address 45: Inter. Monitor Labels: 8E0-951-177.LBL
Controller: 8Z0 951 177
Component: Innenraumueberw. D04
Coding: 00001
Shop #: WSC 00000
VCID: 55DD9ADCBC19
1 Fault Found:
01463 - Alarm triggered by Sensor for anti-theft alarm System
43-00 - Closed
------------------------------------------------------------------------------- Address 46: Central Conv. Labels: None
Controller: 8Z0 959 433 AF
Component: Komfortgerát TBD 1210
Coding: 06859
Shop #: WSC 02138
VCID: 8A6739A0A527
3 Faults Found:
01370 - Alarm triggered by Interior Monitoring
35-00 - -
01561 - Left Rear Door
60-10 - Won't Safe - Intermittent
01561 - Left Rear Door
61-00 - Won't De-Safe
End -------------------------------------------------------------------------------------------------

I have removed the no fault found entries from this list.
Notes:-

1. 17550 error is there.

2. Address 08 Auto HVAC has comm error. You can see it trying to connect but it never does. This has been the case for a long time now though the Heater and Auto AC works fine for temperature but the fan seems to alter in sound and the flaps make bumping or hunting noises quite consistently. I suspect a poor connection somewhere.

3. The Alarm was I think from an accidental triggering incident.

4. The rear left door is a job waiting to be done!

I cleared all the error codes in VCDS but cannot connect to the Auto HVAC module due to the comm error constantly coming up on that.
Drove to the end of the road from cold and both EPC and Engine light came on!
EPC went out after a restart but Engine light remained on for the 10 miles driven today.

The suggestion of brake light switch is interesting as the lights came on as I braked for a T junction but who knows, it's definitely not consistent.
 
I had the HVAC comms error also, using VCDS. I then tried OBD Eleven, and comms was fine, cleared DTCs, and from then on, comms, with either VCDS or OBD Eleven was fine.
No idea what changed, or is different between VCDS and OBD Eleven comms. No other controller is a problem.

If you look at these engine Groups and Blocks, (Groups 060, 061, & 062) that relate to the EPC, you may find a clue.
Take a look at Group 060, Block 04, and see what the adaptation status, (ADP runs/ADP OK/ADP ERROR), is.
Remember, if a sensor is giving a reading that is incorrect, but with the specified range, there will b e no DTC. This is where Measuring Blocks are useful, you can see the individual sensor output, and decide yourself, if it is right for the conditions. Logging is very useful, as the fault might only be present under specific conditions, speed, load etc.

Group 060, Speed Regulation (EPC Adaptation):
060,1,Throttle Drive,Angle Sensor 1,for EPC (G187) | Specification: 10...85 %
060,2,Throttle Drive,Angle Sensor 2,for EPC (G188) | Specification: 85...10 %
060,3,Self-Adaptation,Steps Counter,Specification: 0...12
060,4,Result,Throttle Valve Adp.,Display Range: ADP runs/ADP OK/ADP ERROR
;
Group 061, Speed Regulation (EPC System):
061,1,Engine Speed,,Specification: 800...5700/6600 RPM
061,2,Voltage Supply,,Specification: 12.0...15.0 V
061,3,Throttle Drive,Angle Sensor 1,for EPC (G187) | Display Range: 0...100 %
061,4,Load Status,,see labelfile
; --1xx - Air conditioning system switched on
; --x1x - Driving range (gear) selected
; --xx1 - Air conditioner compressor switched on
;
Group 062, Throttle Angle (EPC System):
062,1,Throttle Drive,Angle Sensor 1,for EPC (G187) | Specification: 3...97 %
062,2,Throttle Drive,Angle Sensor 2,for EPC (G188) | Specification: 97...3 %
062,3,Throttle Position,Sensor (G79),Specification: 0...100 %
062,4,Accelerator Pedal,Position Sensor 2,G185 (Specification: 0...100 %)

Mac.
 
I checked some of these via the diagnostic procedures in the workshop manual (they were within tolerance and seemed to respond as I expected to pedal inputs) but I’ll double check them again tomorrow.

The one of the throttle pedal values only had travel from 14-77%, compared to the tolerance in the manual of 12-97% but other than that behaved as expected…
I can’t remember which sensor (possibly G187) it was so I’ll double check tomorrow
 
Indi said:
I checked some of these via the diagnostic procedures in the workshop manual (they were within tolerance and seemed to respond as I expected to pedal inputs) but I’ll double check them again tomorrow.

The one of the throttle pedal values only had travel from 14-77%, compared to the tolerance in the manual of 12-97% but other than that behaved as expected…
I can’t remember which sensor (possibly G187) it was so I’ll double check tomorrow
Click to expand...
VCDS for the APE/AUA/BBY engine, gives the Accelerator Pedal Position Sensor, G185 a Specification of 0...100 %.
I'd expect Block 04, Group 062 to show it move between 0% to 12% and 97% to 100%, (based on your manual), over the full range of pedal movement
Mac.
 
If I recall correctly the manual was worded slightly vaguely, seeming to say that as long as it went through a range of values between 12 and 97 when the pedal went through its motion then it was within tolerance even if it didn’t cover the full 12-97 range, I’ll plug in VCDS and check it out again tomorrow
 

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