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Serkan

Problem with random E Throttle fault code 76

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Hi, I have tested 2 different cars with 2 different TTlink plug in ECU's  with identical Hemi 80mm throttle bodies. 95% of the time there is no problem at all but sometimes both of them randomly go into limp mode with fault codes 76 and 73. Upon inspecting the logs, I have seen that once in a while there are slight differences between the TPS 1 and TPS 2 readings and I think that these differences are randomly triggering limp mode. Is there any way to change the tolerance of the difference between the TPS readings? Because I initially thought that there is a problem with the throttle body or wiring but having both cars with the same throttle body doing exactly the same thing confused me. Log files of different cars and map file are attached. Thank you in advance for any help.

c Log 2018-04-6 5;03;49 pm.llg

Log 2018-04-6 1;00;26 pm.llg

c 8 4 18 v3.pclr

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Also I wanted to link my previous topic. I was dealing with the same issue actually thought that fault 76 was a result of fault 73 however it was the other way round, because of the tracking error the ecu was shutting down the supply hence fault code 73.. just noticed that I've been dealing with this for more than 1 year :)

 

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Unfortunately there is no setting to adjust the tolerance on this. From memory it is about a 2% difference. And it needs to be different for more than 2 seconds. 

You could check grounds and power supplies to the sensors to confirm that they are remaining the same.

Worst case will be to share a signal across both sub and main. (Warning this does reduce the fault checking / safety features) 

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This is the exact throttle body I'm using on both cars. The 5V and 0V are shared between the two TPS's so does this that the difference between the signals is completely to do with the internals of the throttle body? Also since this throttle body is listed in the help file, I'm assuming that it's been tried and tested?

Throttle body.jpg

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Yep has been bench run to confirm pinout and PIDs. 

It might also be worth rechecking the TPS calibrations are happy at both cold and operating temps. Might be there is some drift with engine temp. 

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Looking at your log I would say either there is a bad connection somewhere or the TP sub sensor has a dead patch.  I know you said you have two cars with a similar problem but I assume we only have the log from 1 car here.

Through 99% of your log TP sub and main track each other nicely.  In certain random areas TP(sub) suddenly drifts away from TP main.  Since they are both connected to the same shaft there is no mechanical way this can happen, it can only be electrical.

In the screenshot below notice up to about 20:28 the TP sub and main are almost sittting dead on top of each other, after that TP sub drifts away (throttle has not moved as RPM stays constant) so the TP error accumulator starts to count.  After about 20:33 the error accumulator has counted up to 100 so it goes into safety mode and shuts the E-throttle power off.  Even after the motor power has been turned off there is still an offset remaining between TP sub & main.

nUdecpD.png

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Yes and the interesting thing is that the logs are from 2 different cars with identical TB's. Thats why I'm thinking it may be the nature of this TB?

When I go through both of the logs,  I see the same drift between the main and sub randomly scattered here and there, just not enough to trigger an error, but once in a while its just too much. 

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I didnt realise you had logs from both cars there, I initially only looked at the "C" log.

Looking now at the second log that shows a different problem, the TPsub/main are tracking good at all times in this car.  The problem in this log is TP/Target tracking error.  This is when the throttle position does not follow the commanded target closely, this is normally PID settings related.  You will just need to tune your PID a little better on this car and it should then work fine without error.

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Just to follow up on the other car which showed better consistency between main and sub signals, I took an ecu log of the problem showing up.. seems very strange .. Everything looks just fine and then suddenly the sub value shoots up

screenshot.jpg

screenshot.jpg

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Yeah weird.  I could only explain this by a dead area in one of the TP sensor tracks.  It is relatively common in high mileage cars as the potentiometer wiper does a lot of work over the small area around idle & cruise.  You might have to follow Simon's advice and connect the TP main sensor to both analog inputs.

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Was there ever a better solution or resolution to this?

I'm running the same throttle body that ran for over a month although I did get one tracking error that I was able to reset and didn't come back until it reared it's ugly head this weekend almost stranding me and ruining a track day.

Tried 2 new throttle bodies with the same issues (well one of the throttle bodies looked really bad).

I'm thinking i'm going to dissect the one throttle body that I have just to see how this is set up internally to see if I see anything odd.

I was able to get home after no issues though basically tuning the PID loop to the APS sub vs the Main. I'm idling at the same type of throttle positions as the original poster 2-3% so i'm wondering if it just don't like being at that low of a position.

 

Also brings up another question I have. How are the TPS Main and Sub signals used? Does the control loop only look at Main and use sub for error checking? is it an average of the 2 signals?

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Essentially the issues is something electrical as the ECU can only work with the signals its given.

The ECU looks at the calibrated % reading off the 2 signals and if it drifts by more than 2% it will start to clock errors. Once it hits 100 errors it will shut the throttle down. (takes roughly 2 seconds to do this if in constant error.

The target is all based off the TP main reading 

 

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20 hours ago, barge said:

Was there ever a better solution or resolution to this?

I'm running the same throttle body that ran for over a month although I did get one tracking error that I was able to reset and didn't come back until it reared it's ugly head this weekend almost stranding me and ruining a track day.

Tried 2 new throttle bodies with the same issues (well one of the throttle bodies looked really bad).

I'm thinking i'm going to dissect the one throttle body that I have just to see how this is set up internally to see if I see anything odd.

I was able to get home after no issues though basically tuning the PID loop to the APS sub vs the Main. I'm idling at the same type of throttle positions as the original poster 2-3% so i'm wondering if it just don't like being at that low of a position.

 

Also brings up another question I have. How are the TPS Main and Sub signals used? Does the control loop only look at Main and use sub for error checking? is it an average of the 2 signals?

Have you got a log showing the sub and main drifting apart like the original poster, or are you just assuming this is the cause of your tracking error?

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I don't have a log handy but over the weekend I was logging and watching a lot because I would get repeated tracking errors.

I can run a TPS calibration. Have the signals overlay perfectly. Cycle power to the ECU and be off 2%. This would almost always manifest as the Sub being at 0% while the main was at 2ish%. (as a note: The error count/accumulation does not increase while it's sitting like this)

They use the same 5V, the same signal ground, and they're a shielded pair inside the same shield. My first thought was a wiring issue but I see no evidence of that. Granted I was potentially stranded hours from home so now that I made it home i'll be able to step back and go through things step by step.

One thing I didn't like to see is that almost every time I calibrated the TPS the settings would change slightly.

I will be doing some more testing tonight and I will try to get some logs but it's seemingly "fine" right now even though the TPS signals are not perfect. I'm beginning to wonder if it's just that this throttle body doesn't like being held at 2-3% throttle opening. (Default opening percentage with motors unpowered is about 8%).

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Hi sorry for being late to reply. In both my cases I concluded that there were problems with the wiring. In the first car, there was a problem with the solder of the sensor ground, in the second car the throttle plug was not seating fully into the socket. In both cases there was electrical continuity most of the time but from what I understand the e throttle system is VERY sensitive. The solder problem and the problem with the plug were randomly creating just enough resistance to trigger the fault. Fixed the problems, re calibrated and no more faults ever since. Hope it helps !

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Thanks... mine is looking to be a wiring problem as well. I'll know more tonight.

However last night test driving my car I lost 5V to every analog sensor. It's all supplied through 1 pin on the stock subaru harness. When i built my new harness I didn't like the look of that connector... just a weak looking pin design and such.

Checked for shorts, none.

Verified ECU output supply value and it was 4.97 if I recall correctly.

No voltage when I checked at the EThrottle Connector. 5V at the bulkhead connector, chassis side.

I'll be replacing all the stock bulkhead connectors with deutsch solid pin connectors tonight then i'll relog. It appears that something in that pin connection gradually became worse and worse until it decided to fail terribly last night. If nothing else it was a giant billboard saying "Issue Here". Seeing as how i'm a controls engineer that troubleshoots electrical systems every day it was a rather frustrating weekend trying to track down what was going on (I reseated this connector several times to ensure i wasn't getting bad connections :/)

I'm still a bit lost as to why the error only seemed to show itself on the sub signal but I guess if both sensors were shifting a bit, with slightly different scaling, it could show some odd numbers.

Sometimes you learn the easy way... sometimes the hard way.

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On 9/17/2019 at 3:42 PM, Serkan said:

Hi sorry for being late to reply. In both my cases I concluded that there were problems with the wiring. In the first car, there was a problem with the solder of the sensor ground, in the second car the throttle plug was not seating fully into the socket. In both cases there was electrical continuity most of the time but from what I understand the e throttle system is VERY sensitive. The solder problem and the problem with the plug were randomly creating just enough resistance to trigger the fault. Fixed the problems, re calibrated and no more faults ever since. Hope it helps !

Did you log afterwards and see the signals tracking over each other.

I believe I've resolved my 5V issue noted above. I've got some new connectors coming in just to make sure the Ethrottle connection is solid... but i'm still seeing some inconsistencies in the sub sensor. I test drove the car after and i'm not seeing any faulting. Some momentary error count blips.... but the issue is so random that it will work "fine" for a day... then the next day be nothing but fault fault fault. So i'm not very trusting in functionality right now.

I did not that for some reason the main signal is shielded in the chassis harness for the vehicle but the sub is not. They are both shielded together in my engine harness.

I'm going to put some miles on it tonight to see how things look and i'll get some logs posted as well.

 

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