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2010 Suburban 75th Diamond Edition
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17 Posts
Discussion Starter #21
I hate to sound like a newb, but would i need to remove the part from the car to test it with a ohm meter? Whats the difference in using the ecm sensor data vs an ohm meter?

The absolute throttle position sensors measure how open or closed the butterfly valve in the throttle body is.

Here is a graph with the 2 outputs from the pedal position sensor, the quotient of those 2 signals, as well as the absolute throttle position.

When the graph show the throttle position anomaly the pedal sensors quotient in near 2, which mean that both outputs from the pedal sensor where correct at the time the TPS signal dipped very low.

But on this graph you can see a huge mismatch in output 1 and 2 of the pedal position sensor.. I circled it in orange on the quotient graph.. During that time while I was driving, I did experience a lag in acceleration then followed by a jerk...

How could I find out if all those small variances on the quotient graph are within spec? Is there not some document that I can read that will tell me what is acceptable or not?

I think the only way I will be able to find out if my pedal is out putting the correct signals is maybe order a new one, install it and run the same test..

167634
 

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I'm not an expect; but I would guess your seeing the TPS input from the pedal position sensor.
As I said earlier, an ohm meter will tell you if the position sensor is smooth, or has open spots.
A new sensor is probably $40
Ok, I've done a little reading.
The TPS is told what to do by the APPS, as the gas pedal is operated, the throttle butterfly follows.
However, this we haven't talked about, the TPS has a variable resistor that tells the ECM where the butterfly is in relation to fully open, or fully closed.
So @Bionic , the graft you have been posting is the output of the TPS, not as I was guessing, the output of the APPS

And, from what I've been reading, a graft like the one you posted should be throwing a code, a code between P0121 and P0124.

If one of those 4 codes is present, the TPS should be changed. And, as I said earlier GM has a program were they will change it for free.
 

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2010 Suburban 75th Diamond Edition
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Discussion Starter #23
@RayVoy . I have posted graphs for both.. The APP and the Throttle Position. If you look at the post 21 above, that graph has the 2 outputs for the App, 1 output for the throttle position, and 1 line graph that represents the quotient of the 2 App outputs.

I have no codes. So if the sensors are bad they are recovering from the error state quicker that the ecm will put it in an error state an post a code for it.

Perhaps the graphs that I am getting is completely normal.. I dont know... but what I did do was order an new APP and amazon just delivered it.. I am going to install the new one and graph the outputs and see if there is a difference.
 

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Discussion Starter #24
So I just replaced the APP, and I am currently on a test drive.. The car idle is steady! It seems like I can accelerate smoother from the stop lights, I haven't experienced any weird shifting or acceleration while braking!

I am logging data.. so once I get back home I will download the data being output now with the new app vs the data I have with old app.
 

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Discussion Starter #25
Here is a new graph with the new APPS installed..

I did not include the Output 1 and Output 2 of the APPS. I only include the Quotient of the APPS, because the quotient graph is where you will be able to detect the problems.
Look how straight the blue Quotient graphs is now! That means that the 2 outputs of the APPS is outputting the correct synced signals levels.

I also included to Absolute Throttle Position % in red. This represents how open the throttle body butterfly is open.. The 2 flat top peaks, is when I went WOT merging on the freeway!

Everything looks good and the car is driving a lot better. Will continue logging and analyzing the data for the next few days. But as of right now, I consider this fixed!

Thanks for yalls help, pointing me in the right direction! The advice to get an OBD Scanner and start plotting the output of the sensors put me on the right path!

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Some of what he described sounded like a bad wheel speed sensor. Similar to things I had when mine went bad. But I don’t think that’s cause a rough idle or surging? Idk
 

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Discussion Starter #27
Quick update..
Before I replaced accelerator pedal & sensor my gas mileage was 12.3 mpg on the DIC.
After I replaced it a few days ago, my gas mileage is now 14.3mpg!

Having better gas mileage would make sense now, because I haven't experienced the surging feeling or auto acceleration issues anymore.

Also, I have always needed new brake pads kind of quickly (to me it seems).. I bet me braking while the car car is still trying to accelerate or having a high idle was the reason my brake pads would wear out quickly. In all my research I did, I didn't see early brake pad wear as one of the symptoms of a faulty Accelerator Pedal Position Sensor, but I guess it could be and would be a logical symptom.
 
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