Throttle Sensors vs Wire Round 7 - SOLVED

[OBSandaNNBS]

Been a lurker here since I bought my lady a rather clean 2012 Tahoe LS three months ago. 156K miles.
I'm above average mechanically inclined for being a [cough] mellenial, but untill now have always run older vehicles (IE a 263K 97 Burb) for ease of repairs and noted lack of sensor issues...

Two weeks or so ago, Check engine light came on and went away in the same drive. I checked with my entry level scanner anyway. It gave P0121, Throttle/Pedal Position Sensor/Switch A Range/performance problem. General online consensus is clean the throttle body.
I put it off (NOT ADVISED!!) then two weeks later, it went into limp home.

The DIC told me:
"Reduced Engine Power"
"Service Stabilitrak"
"Service [something else]"

The wife told me:
"This better not be from running it in M5 mode!!"

In addition to low power, it was lurching badly when downshifting from 2nd to 1st and worse when coming to a stop in 1st.
The scanner gave P2135 "Throttle/Pedal position switch/Sensor A/B Voltage Correlation"
I yanked the throttle body off and cleaned it. Smacked it back on and attempted the 3 minute idle-1 minute rest-3 minute idle-drive above 45 for a few relearn procedure. Limp mode was gone, however it still was lurching.

Okay, improvement, but not fixed. I got home, shut it off.

Now here's the recurring problem:
Immediately after, I restarted just for the heck of it and it flew up to 3000 RPMs at idle, slowly climbing to 3500. I shut her down and went inside to scratch my head.

I ended up replacing, in order, the TB postion sensor, the connector at the throttle body-soldered (live data showed the TB % jumping around while I wiggled it), and Pedal Position Sensor. All ACdelco except the Throttle Body Position sensor, which is Duralast. I tested the Duralast unit while on the truck through the new connector with my multimeter and it seems A-OK. I have an ACdelco TBPS too just in case.

Before each replacement, i disconnected the battery and let the engine cool overnight. After each replacement, the EXACT same 3K idle problem occurred after attempting the relearn. It's always when engine is hot after the drive portion of the relearn.

I remembered to replug in the PCV line before swapping the connector. May be responsible for the early P0300 misfire code, not sure?

I've got the following codes right now:
P0122 Throttle/Pedal position Sensor/Switch A circuit LOW
P0233Throttle/Pedal position Switch/Sensor B circuit HIGH
P0300 Random/multiple misfires
P0507 Idle RPM higher than expected (no kidding)

Now I'm thinking that either:
A) relearn procedure is not working correctly, I'm not really willing to see if it "figures itself out" while acting like that (3500 rpm) and throwing codes.
but more likely
B) I've got a phantom bad wire. The wire split loom absolutely crumbled where it ran above the valve cover.

I had put off investigating the harness because swapping sensors is easy. I checked about 2 feet of it from the TBPS to the back of the valve cover and it visually looks fine, just a little dirty.

I also haven't replaced the throttle body itself (don't know how to test), or the PCM. Both of which are on the list of possibilities.

I figured I'd ask the giants here so I might stand on a shoulder...

Thanks in advance!

 

[mikez71]

If you replaced the TPS already, make sure it is installed right. I believe you need to open the throttle fully when installing.
Do you still notice the sensor data jumping around when you wiggle the wire?

 

[OBSandaNNBS]

Thanks for the reply!

I was careful to open it while installing but now I'm not 100% sure. I'm going to try again right now.

My scanner shows a ton of stuff for being so cheap, I just don't know what the abbreviations mean

Do you have a scanner recommendation that won't break the bank?

 

[j91z28d1]

with fly by wire stuff I don't even try to fix tb or pedal when they go into reduced power more. Just toss in a new oem of which the code says.


so far it's always fixed them.



on a side note I know there was a thread a few months back where a guy said the more he ran the idle relearn the worst it got over time. I'm not sure what to search for thou.

 

[OBSandaNNBS]

If you replaced the TPS already, make sure it is installed right. I believe you need to open the throttle fully when installing.
Do you still notice the sensor data jumping around when you wiggle the wire?

Just saw that last question- no, after replacing the connector, the change from wiggle apparently disappeared.

 

[OBSandaNNBS]

with fly by wire stuff I don't even try to fix tb or pedal when they go into reduced power more. Just toss in a new oem of which the code says.


so far it's always fixed them.



on a side note I know there was a thread a few months back where a guy said the more he ran the idle relearn the worst it got over time. I'm not sure what to search for thou.

I def agree. I have never had a problem with drive by cable on my 4 vehicles that had it. All over 150K, most over 225K.
I was more trying to troubleshoot after the expected replacement didn't work...

 

[OBSandaNNBS]

If you replaced the TPS already, make sure it is installed right. I believe you need to open the throttle fully when installing.
Do you still notice the sensor data jumping around when you wiggle the wire?

Well shoot if that didn't seem to work!! I just got back from the drive and it *DID NOT* over rev on idle. Its still a little lurchy but I think that will (hopefully) sort itself out.

MikeZ71, THANK YOU SIR!

 

[Fless]

Well shoot if that didn't seem to work!! I just got back from the drive and it *DID NOT* over rev on idle. Its still a little lurchy but I think that will (hopefully) sort itself out.

MikeZ71, THANK YOU SIR!

I'm tagging @mikez71 to be sure he sees this. When you tag a member, start by typing the "@" symbol, then start typing the username. A list of matches should display and you can pick the correct one on that list. Otherwise the target member may not see your post.

 

[mikez71]

Glad it seems to be working, thanks for tagging it for me Fless! This board is a great resource! I try to fill in what I can to give the old regulars a break. Its usually stuff I read about from here!

 

[OBSandaNNBS]

Ay! The problem is back... Slightly different, revs on startup to 1500 for 1 min then up to 3000. I'll update once I find the solution for those who see this thread in the future...

 

[OBSandaNNBS]

I'm tagging @mikez71 to be sure he sees this. When you tag a member, start by typing the "@" symbol, then start typing the username. A list of matches should display and you can pick the correct one on that list. Otherwise the target member may not see your post.

@Fless
Haha thanks! I was wondering since I didn't see any replies w/o refreshing.
In my defense on the last post, my browser hadn't refreshed.

 

[Joseph Garcia]

Did you inspect ALL of the electrical ground points on the motor and in the engine bay to ensure that they are clean and tight? Many otherwise unexplainable issues end up being ground-related issues.

 

[mikez71]

Also, there maybe a TPS relearn procedure that needs a scantool.. or

How to perform a GM throttle body relearn procedure

Learn how to do a GM throttle body relearn to establish a new baseline idle after replacing or disconnecting the throttle body.

ricksfreeautorepairadvice.com

1) Start the engine and let it idle in park for 3 minutes. During that period the idle may be higher idle than normal.
2) After 3 minutes, turn the engine off and leave it off for 60- seconds.
3) Start the engine again and let it idle in park for 3 minutes one more time. During these run periods, you may see a check engine light. Scan for codes and if you get throttle body-related codes, clear them.
4) If the idle speed is still off, drive the vehicle at speeds above 44 mph and operate several acceleration and deceleration cycles. Then repeat step #3 one last time.

 

[89Suburban]

Good job @mikez71 .

Here is a good detailed video about the TPS install and how to clock it properly. Saved my asz.

And some pics of my TPS's, note the difference in the clocking of the sensor hub. Also those brass connectors can loosen up as well.

What did you do to your NNBS GMT900 Tahoe/Yukon Today?

I'm back from my trip into the Berkshires and Adirondack mountains, and I got some good insight into my current 4.10 gears and supercharger setup. My mileage with the 4.10 gears and supercharger was 15.3 mpg on the trip, and that compares to 17.1 mpg on a previous trip with 3.42 gears and the...

www.tahoeyukonforum.com

 

[OBSandaNNBS]

Did you inspect ALL of the electrical ground points on the motor and in the engine bay to ensure that they are clean and tight? Many otherwise unexplainable issues end up being ground-related issues.

@Joseph Garcia
No I didn't. This is one of those times you can look back on and say, "That's how I learned that."
So thanks!

How many of these things am I looking for?

 

[OBSandaNNBS]

Also, there maybe a TPS relearn procedure that needs a scantool.. or

How to perform a GM throttle body relearn procedure

Learn how to do a GM throttle body relearn to establish a new baseline idle after replacing or disconnecting the throttle body.

ricksfreeautorepairadvice.com

1) Start the engine and let it idle in park for 3 minutes. During that period the idle may be higher idle than normal.
2) After 3 minutes, turn the engine off and leave it off for 60- seconds.
3) Start the engine again and let it idle in park for 3 minutes one more time. During these run periods, you may see a check engine light. Scan for codes and if you get throttle body-related codes, clear them.
4) If the idle speed is still off, drive the vehicle at speeds above 44 mph and operate several acceleration and deceleration cycles. Then repeat step #3 one last time.

@mikez71
Thanks, that is the exact procedure I used. It's only doing the high rev after the engine is hot. Wait 20 min and it is normal. I think you and 89suburban are onto something with the "install it correctly" idea. I'm going to start over with my ACdelco sensor.

 

[OBSandaNNBS]

Good job @mikez71 .

Here is a good detailed video about the TPS install and how to clock it properly. Saved my asz.

And some pics of my TPS's, note the difference in the clocking of the sensor hub. Also those brass connectors can loosen up as well.

What did you do to your NNBS GMT900 Tahoe/Yukon Today?

I'm back from my trip into the Berkshires and Adirondack mountains, and I got some good insight into my current 4.10 gears and supercharger setup. My mileage with the 4.10 gears and supercharger was 15.3 mpg on the trip, and that compares to 17.1 mpg on a previous trip with 3.42 gears and the...

www.tahoeyukonforum.com

@89Suburban
Thanks! One of my terminals came off too.
Funny, I actually came across that bulletin he used in the video today but disregarded it because it applied to 08-11 models (mine is 12) but it still has relevant info.

I think I just put it on clocked incorrectly.

Man, if that's the case I'm going to be embarrassed!

 

[mikez71]

No reason to be embarassed! GM just makes things complicated to screw with us.
Nobody in their right mind knows this crap until it happens and they have to deal with it..

 

[OBSandaNNBS]

"GM just makes things complicated to screw with us."
LOOOOOOOOOLLLLLLL ain't that the truth!

I popped the AC Delco sensor on. The quality difference was noticable.
Not sure if I'm out of the woods yet, gonna drive it tomorrow to shake it out.

 

[89Suburban]

> fingers-crossed <