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2011 impala 3.5L & 2007 trailblazer 4.2L exibiting the same…

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2011 impala 3.5L &...

2011 impala 3.5L & 2007 trailblazer 4.2L exibiting the same symptoms - can not control throttle body. Changed throttle body & PCM with no results. Scanned PCM, APP is present but no throttle plate movement on either vehicle. APP movement is being picked up by PCM - checked wiring OK - Can move throttled plate by hand & see movement on scanner WHAT's WRONG

Mechanic's Assistant: Have you checked all the fuses? Do you have a wiring diagram?

Yes

Mechanic's Assistant: Are you fixing your Trailblazer yourself? What have you tried so far?

Changed throttle body & PCM, checked wiring for continuity OK

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Can't get the throttle to relearn because I can't control RPM's

Submitted: 4 months ago.Category: Chevy
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Answered in 4 minutes by:
12/14/2017
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago
Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 7,251
Experience: ASE master tech for 40 years
Verified

hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

ok

did you change the pedal assembly?? this is what controls the throttle body movement. the pcm may see the tps working but the pedal module controls the commands.

Roy

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Customer reply replied 4 months ago
Even if i see movement on my scanner that the pedal is moving
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

your seeing a reading for the tps sensor voltage change on the throttle body.

Roy

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Customer reply replied 4 months ago
I see sensor voltage change when i move the throttle plate manually, i see pedal voltage change on my scanner as i depress the pedal - when i press the pedal no change at throttle body
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

I see what you mean but the module is not commanding the motor to open.

Roy

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Customer reply replied 4 months ago
Exactly, I've actually had a mobile programmer try to reprogram the throttle body with no results - he suggested a wiring problem but i have continuity with all wiring
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

its not the throttle body. the control module is part of the inside pedal assembly.

Roy

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Customer reply replied 4 months ago
That might explain the no throttle movement but it doesn't explain the erratic idle
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

2 separate issues. nothing listed in your post for a rough idle

Roy

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Customer reply replied 4 months ago
All these problems started at the same time, started vehicle it an rough and could not accelerate, changed throttle body first, then PCM
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

get the throttle body resolved first and then drive it to see if the rough idle still exists. the module will position the plate correctly to adjust idle speed and smooth.

otherwise there is another issue. first things first

Roy

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Customer reply replied 4 months ago
i'll give a shot will get back tomorrow to let you know how it goes
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

ok

Please take a moment and rate my service 3 stars or better. that is the only way the site will pay me for my efforts.

Roy

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Customer reply replied 4 months ago
I'm guessing it's 3 out of 5 stars - it was worth at least 3 stars - if it works i'll give you 5 stars but i won't get any parts until tomorrow - worth the conversation - thanks
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

your welcome

when you rate hit the number of stars at the top of the page

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

any update???

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Customer reply replied 4 months ago
OK tried the accelerator pedal - it did not wok
Customer reply replied 4 months ago
the initial problem of erratic idle and unable to accelerated remains - i'm at a loss
Customer reply replied 4 months ago
roy are you there ?
Customer reply replied 4 months ago
Roy - still waiting for an answer
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

yes, I am here. was on phone with another customer.

did you verify 5 volt reference at the app?? there are tan, white/black and gray wires. they all need 5 volts key on.

please be patient as I answering many questions.

Roy

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Customer reply replied 4 months ago
5 volts are present and i see voltage change on my scanner as i depress the pedal
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

ok

is there any voltage on the tan wire at the throttle body???

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Customer reply replied 4 months ago
all 5 volt references are present
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

no, my question was is there voltage on the tan wire at the throttle body???

what voltage do you have at the motor wires on the throttle body???

Roy

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Customer reply replied 4 months ago
8 wires - blk/wht 0v - gry 5v - brn .245v - yel 0v - ppl 4.30v - blk 0v - blu/blk 5.0v - grn .014v that come from throttle body
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

are you sure the blk/wht is not a white/black??? in the diagram I sent you it should have 5 volts from the pcm

Roy

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Customer reply replied 4 months ago
i'm checking the 2007 trailblazer (the 2011 impala has the exact same problem) there is no white/black wire
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

wish you would have told me that

let me get the info from that

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Customer reply replied 4 months ago
we discussed this from the very beginning
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

you listed both cars in your original not mentioning which one you were actually checking

my concern is no power to the motor wires for moving the plate. that comes directly from the pcm to the throttle body.

when you command the throttle plate open with the scan tool can you check the power on those wires???

Roy

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Customer reply replied 4 months ago
i checked that earlier, there was no voltage change at throttle body. tried manually moving throttle plate with 12v power & ground the throttle plate moved accordingly
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

then that tells us the pcm is not working sending the signal. thats where it comes from.

you said you verified wiring was good so that leaves only the pcm. I assume you flashed the pcm to the vin number of the truck.

Roy

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Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

ok, then it looks like you have a bad pcm

Roy

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Customer reply replied 4 months ago
on the impala i changed both the PCM and the throttle body with no results, i took apart the wiring harness to physically check the wiring from the PCM to the throttle body which on the 2011 impala 3.5L are basically ight next to each other and found no problems with continuity or voltage
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

ok

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Customer reply replied 4 months ago
Roy, any good news today ?
Chevy Mechanic: Roy, import/domestic specialest replied 4 months ago

no, I cannot continue since I am here and not there. I need to see it, touch it and test it myself in orer to resolve this. I will opt out and see if anyone else has any ideas.

Roy

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Chevy Mechanic: Todd Audette, Chevy Technician replied 4 months ago
Todd Audette
Todd Audette, Chevy Technician
Category: Chevy
Satisfied Customers: 414
Experience: Chevrolet Technician
Verified

I can try to help you but we need to be working on 1 car at a time

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Customer reply replied 4 months ago
which vehicle would you like to start with (2011 impala 3.5L or 2007 trailblazer 4.2L) both have the same symptoms cannot control the throttle plate with accelerator pedal or mato maximus 2.0 scanner even though voltage change while depressing pedal or manually moving throttle plate
Chevy Mechanic: Todd Audette, Chevy Technician replied 4 months ago
Impala first. I'm at work so I'll be on and off when i can. Any codes in the impala
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Chevy Mechanic: Todd Audette, Chevy Technician replied 4 months ago
There's a 14 pin connector on the top of the drivers strut tower that goes between the accelerator pedal and ecm. Check that make sure no loose terminals, corosion etc
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Chevy Mechanic: Todd Audette, Chevy Technician replied 4 months ago

Do you still need help or are you good

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Customer reply replied 4 months ago
Checked connector on strut tower OK
Chevy Mechanic: Todd Audette, Chevy Technician replied 4 months ago
let me get this straight. When the car is running you have no throttle response or just when the key is in the on position
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Customer reply replied 3 months ago
all the time
Chevy Mechanic: Todd Audette, Chevy Technician replied 3 months ago
Have you ohm tested the wires end to end from the ecm to the pedal
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Chevy Mechanic: Lou P., ASE Certified Technician replied 3 months ago
Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 5,721
Experience: Building and driving Chevy's since I was in the womb!!!! Camaro and Corvette enthusiast, access to factory diagrams and tsb's
Verified

Hello Al, it seems you have quite the issue,

looking over the chats I know I can help, But when the techs ask you questions you do not answer them, you seem to reply with some other info that was not requested.

so I can help, I will want to start off as if you NEVER worked on the car at all.

first thing I will want to do is the 2011 impala.

start the car, use the scan tool to run the codes. report back to me the codes and we can go from there.

fixing issues like these are not complicated. but they can be if we do not stay on the same page and do things in order slowly. not to get ahead of each other and keep open clear communication.

I am willing to work with you to resolve this.

so 2011 impala, start it and press the gas pedal a few times to verify no operation and then run the codes to see what codes pop up in ALL modules., not just the ecm.,

Lou

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Customer reply replied 3 months ago
OK lou, i'm back. scanned the 2011 impala 3.5L codes p0315, p0523, p1516, p2101, p0122, p0222, p0223 (sorry it took so long it's the holidays)
Chevy Mechanic: Lou P., ASE Certified Technician replied 3 months ago

no worries i am in the same boat :)

looking over the codes now and thanks for working with me on this.

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Chevy Mechanic: Lou P., ASE Certified Technician replied 3 months ago

ok my man here are the code descriptions.

the important ones are pretty much all but the crank sensor one at the moment and the oil pressure one.

the codes indicate to me wiring issues.

so take a look over the info I am sending over.

we need to verify the voltages with a scan tool and meter on the physical connections.

now in my experience with all of the GM fly by wire cars the issue is one of 4 very common failures

  1. throttle body
  2. throttle body connector/terminals (napa has a repair kit)
  3. accelerator pedal
  4. accelerator pedal connector/terminals (napa as well)

so lets take a real good look at the wiring, and also the voltage.

since you have a new part (hopefully NEW GM) and not reman or used then we need to verify that the voltage is correct.

also history of how this happened would be best too.

but these codes are the money shot.

if you have any question about the testing let me know i will do what I can to advise

Lou

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Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 5,721
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Experience: Building and driving Chevy's since I was in the womb!!!! Camaro and Corvette enthusiast, access to factory diagrams and tsb's

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