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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29572
Experience:  GM Grand Master Technician 2007. 14 years experience.
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My apps is acting wierd no codes but no pedal if t clear on

Customer Question

my apps is acting wierd no codes but no pedal if hit clear on scanner will have pedal for a few seconds
Submitted: 2 years ago.
Category: GM
Customer: replied 2 years ago.
accelerator pedal position sensor is what i mean by apps, i have power on one of the pins with a test light, when i unplug the sensor i get a reduced engine power message on the dash, when i hook my scanner to it says no codes if i hit clear i get throttle for a few seconds then it goes away till i hit clear again yet still no codes on scanner or check engine light on the dash this a 2005 chevy 3500 6.6 lly duramax
Expert:  GM Tech (Cam) replied 2 years ago.
Hello, I'm Cam.
Can I get your first name please?
So the fault may not set the CB eck engine light but does your scanner show you if any codes pending? The issues that I've seen around this with the pedal position sensor itself, the wiring to the sensor, or as strange as it sounds the turbocharger position sensor. The Accelerator pedal position sensor uses three different sensors inside of it, each with a separate 5 V reference. One of the other sensors sharing any of these reference voltages could be dragging that voltage down in setting this issue. Finding which one could be a pain, and have to use the scanner that will view live data from the engine control module, and from there we see which sensor. The computer supplies and monitors each five reference, so if one of them is low then we need to change that one down.
Customer: replied 2 years ago.
my name is ***** ***** what should i try now?
Expert:  GM Tech (Cam) replied 2 years ago.
the next step Justin is to figure out which voltage is down. To do that we need to get our hands on a full function scan tool that shows all of the ECM values including the Five volt references I spoke about.
Customer: replied 2 years ago.
ok so hook it up and then do what?
Expert:  GM Tech (Cam) replied 2 years ago.
You hook the scan tool up and then navigate to the live stream where you would see engine speed and throttle position and such. You will navigate down to the reference voltage is in with the key turned on but the engine off, tell me what the voltages for reference one, reference two, and reference three. From there I can tell you which sensors share the same reference voltage so that you can start unplugging the sensors to see which one returns the voltage to normal. If one of the sensors it shorted out inside, it would drag the whole line down.
Customer: replied 2 years ago.
this scanner im using has live data but wont let me click on it trying to find a good one
Expert:  GM Tech (Cam) replied 2 years ago.
Ok.
Customer: replied 2 years ago.
ok got a good scanner getting code p0101 which is mass air flow sensor do you think this may be the cause?
Expert:  GM Tech (Cam) replied 2 years ago.

Yes, very possible. Is the air filter plugged? Dirty Mass Air Flow sensor (MAF) sensor in the duct? Plugged exhaust? charge air cooler line popped off?

Customer: replied 2 years ago.
its a twin turbo truck
Expert:  GM Tech (Cam) replied 2 years ago.

Its modified to add a second turbo? Factory it only came with one.

Customer: replied 2 years ago.
its a built truck has compound turbo setup
Expert:  GM Tech (Cam) replied 2 years ago.

OK, so lets check that Mass Air Flow sensor (MAF) sensor then. I am not sure where it would be in your setup, does this share a single air filter?

Customer: replied 2 years ago.
what do you want to check on it the air flow or what?
Expert:  GM Tech (Cam) replied 2 years ago.

Dirt on the sensor, even consider unplugging the sensor and see what that does.