Problematic P2135 code

All right, so I'll lay on my issue as plainly as I can. As the title states, I'm having a p2135 on our 2003 Denali XL.

As I initially started to diagnose this issue, I started with the obvious things like throttle body and then eventually throttle pedal position sensor. While changing these, noticed that they have both been done before as well as the pigtail for both under the hood and under the dash for both TPS sensors have also been replaced added grounds from PCM to chassis engine to chassis multiple places under the hood trying to eliminate a grounding issue. Yet this problem still persists and I believe is getting worse.

Trying to chase this down, whether it's a wiring issue PCM issue or exactly what I'm not sure, but I'm wondering what other PCM would be compatible. I do have HP tuners and as long as it's a fellow 2003 Yukon PCM I have The ability to write the file easily. Also using the HP tuners. I have done a little data logging although the issue is not presenting itself to me in an obvious manner.

One of the things I have not tried yet is to pull the fuse box. Look underneath it for any culprit wires. Otherwise I'm starting to be at a loss. However, I also will have a 2003 suburban with a 5.3 coming into my possession and I'm wondering how to check to see if the wire harness is the same possibly swap that if I have to.

Have you been able to log when the code pops up?
And are you saying you have a new TPS and pedal sensor?
TAC or throttle actuator control module might have something to do with those signals?

mikez71 said:

Have you been able to log when the code pops up?
And are you saying you have a new TPS and pedal sensor?
TAC or throttle actuator control module might have something to do with those signals?

Click to expand...

Yes I have been able to log while it tripped the code. Twice. While logging also reset and it comes back to normal.

I forgot to mention that these days when it tripps the code it goes to reduced power, but at idle runs absolutely lousy ( has even died at idle). Once reset ( while still running goes right back to normal.



As for parts replaced, yes I put a TB on . and discovered that it had been replaced before. As well as the dorman style harness repair plug under the hood.


After this didn't fix I moved to the pedal position sensor and diacover d all the same things. The sensor and pigtail had been replaced before.


I stared by adding the grounds as rig terminals and wire are usually on hand.


Have not tried the tac as of yet. But I do have a good one on my Tahoe that I could swap to try ( maybe see if it gives the Tahoe the same issue.

mikez71 said:

Have you been able to log when the code pops up?
And are you saying you have a new TPS and pedal sensor?
TAC or throttle actuator control module might have something to do with those signals

Click to expand...

after doing some more research, not sure how i have overlooked this, i will be swapping the known good one from my Tahoe, possibly tonight to see if that does the trick. ( if it does i have a whole parts suburban coming and the Yukon is in much better physical driving condition as i need some rear brakes, axle seal, and a couple other little things for it to remain in good driving condition. and honestly if i can make the Denali drivable easy then i will just make our grand prix run and will swap between it and my Goldwing for the time being and probably focus on fixing my 01 Sierra instead of the Tahoe for now. so thank you for spiking my absent brain. )

bigdog9191999 said:

Yes I have been able to log while it tripped the code. Twice. While logging also reset and it comes back to normal.

Click to expand...

How do you have to reset it? Key off and on?

So no discrepancies between desired throttle position and actual? And no weirdness in pedal position?

For the check engine light I have an aero force scan gauge that can read and clear basic codes. This is what we have been using.


When I had hpt logging it the other day I just used it to reset ( while I was logging, to see if there was a parameter that was obvious before/after ( not that my novice hpt eye saw)).

And so far I have swapped modules after I got home. Drove them both around the block ( is like a 5 mile loop in the country). And they both acted fine.. so guess it's back to drive till someone acts up again. ( Need to see if I can find my dongle so I can have the gauge in one and torque on my phone for the other , not knowing which truck will act up for sure. ).

Nothing useful in the freeze frame record data?

TJ Baker said:

Nothing useful in the freeze frame record data?

Click to expand...

Great idea! Totally forgot about that, even though I've recently been checking mine for various codes...

Looking at photos of my freeze frames, they always show accel pedal position (average & indicated) and throttle position (desired & indicated)..

Unfortunately hptuners VCM scanner software doesn't show it. I had to use my Tech2, but hopefully other decent enough scanners will show it...

mikez71 said:

Looking at photos of my freeze frames, they always show accel pedal position (average & indicated) and throttle position (desired & indicated)..

Click to expand...

It would be even more useful if they showed the the individual sensor data.

I sometimes use an OBD2 dongle with the Car Scanner app to capture sensor data for review and analysis.

Well the two indicated positions should be sensor data, but only one frame..

If indicated and actual TPS don't match, it should be the TPS, or TAC, or associated wiring... Kinda narrows it down?

Yep, I definitely like graphs much better! I can only recommend graphing scanners, because it would be so easy to miss things only watching numbers bounce around, at too slow of a refresh rate.

mikez71 said:

Well the two indicated positions should be sensor data, but only one frame..

If indicated and actual TPS don't match, it should be the TPS, or TAC, or associated wiring... Kinda narrows it down?

Yep, I definitely like graphs much better! I can only recommend graphing scanners, because it would be so easy to miss things only watching numbers bounce around, at too slow of a refresh rate.

Click to expand...

Particularly useful catching poor connections. Here I caught a bad connection on a low reference circuit from a 4WD encoder signal.

You can tell it was the low reference by the direction of the spike. Lose the low reference and the sensor voltage shoots high. Lose the 5 volt signal and the sensor voltage goes to 0.

Alright, first change of luck. Since swapping the module Ran well all the vehicles a bit , esp waiting for the Tahoe to pop a code. ( Hoping for that module to be bad. ).

And the Denali finally went again. But gave more codes again this time. (Wasn't logging. ).

P0101 for maf circuit
P0120 for TPS malfunction
And our old friend
P2135



Side note, I do have a dongle if there is an app that can see it. ( I do have torque pro)

Did you swap TAC modules already?
There could be differences between them since one is a 6.0 and one is 5.3.
But if you find the part numbers are the same, maybe you can swap some parts around...

..assuming you don't get the scanner setup to log throttle and pedal positions.
Sorry I don't know what software works with what hardware regarding scanners..

Both pedal and throttle connect to the TAC module directly though, so I think it's likely to be the TPS and/or TAC module?

P0101 likely needs a new MAF. Mine was over-reporting at idle and under reporting at WOT compared to a new one.
A new MAF seems to have fixed it (it's only been a few days), but also I have been told the sensors age out...
(You can check your long term fuel trims too, mine were high with the old MAF)

mikez71 said:

Did you swap TAC modules already?
There could be differences between them since one is a 6.0 and one is 5.3.
But if you find the part numbers are the same, maybe you can swap some parts around...

..assuming you don't get the scanner setup to log throttle and pedal positions.
Sorry I don't know what software works with what hardware regarding scanners..

Both pedal and throttle connect to the TAC module directly though, so I think it's likely to be the TPS and/or TAC module?

P0101 likely needs a new MAF. Mine was over-reporting at idle and under reporting at WOT compared to a new one.
A new MAF seems to have fixed it (it's only been a few days), but also I have been told the sensors age out...
(You can check your long term fuel trims too, mine were high with the old MAF)

Click to expand...

i replied to this the other day, but apparently it didn't go through from my phone.

i swapped modules and it took time, but it was the Denali that gave the codes, not the Tahoe, it has been a couple days and Tahoe is still doing fine on the Denali module so guessing that isn't the issue.

i have some data log from hpt, but not really sure i am seeing where the issue is. i put a tb on the truck last fall, so i would doubt it is the issue, but i may swap it for the one on the Tahoe just because i know it to be a good working unit. same with the maf.

all the parts i have looked up all cross as the same so far in regard to all these items, so i am lucky there.

also, very soon i will have what i believe to be a running suburban (same year as both ours even) that i should be able to swipe things off ( or make run and drive it a little)

i do have the last tb i took off and i may also just get a sensor and toss on it (way cheaper that a whole tb) then i will have a spare.



i am honestly starting to wonder if there is a pcm issue, or in the harness. possibly losing the 5v reference, then showing a discrepancy. ( if the harness is the same i would be willing to swap the harness from the suburban into the denali)



bottom line is the Denali is a Florida truck ( being we live in Michigan) so i will be doing what i have to, to make it work even if that means roto rooter the wiring or whatever to get it there.

On one hand, it would be nice to know which circuit has the issue..
But on the other hand since it's so intermittent, you could be logging for days!
Swapping parts may or may not work if it's a wiring issue..

I would log the pedal and throttle positions and desired throttle position.
Positions 1&2 or A&B. Look for any sudden spikes that look out of place, or a mismatch between desired and actual positions..

Since you said all the usual suspects have been replaced once before, it likely is something deeper.
You might try logging with the motor off, or at idle, and wiggle all the wires you can.
Pull as much wire free as you can..

This thread mentions a smashed wire from the pedal behind a junction block on the firewall.

Note that the APP #1 and #2 (and also the TPS #1 and #2) values are inversely related; when one goes higher, the other goes lower. In the graphic that @TJ Baker posted in #10, they each vary from their respective high/low voltage by the same amount.

In other words, when one APP value is 1v higher than the low voltage, the other is (or should be) 1v lower than the high voltage. This provides for sensor accuracy validation, so when one is not tracking the other, it can give fair warning of an issue with throttle commands.

well some minor updates, however confusing to me too. something that i had suspected bu wasnt sure how to dive into was the remote start.

the remote start on this truck uses the oem fob, and on the double press of lock when it would honk the horn, also activates the remote start. since i did the module swap we have been specific to not use the remote start at all, only lock and unlock. and we have driven 4-5 separate trips of 30 ish mile round trips with no issue.

i wonder what this may or may not have done for things. something i also did after swapping the module and getting the code, was that i pulled the fuse box cover and the box to inspect for damaged wires or such. although i didnt find any. i was prepared to start swapping maf and even the tb from the hoe to the denali as both are proven reliable units.

if we have several more trips that are without code then i will use the remote start predominantly to see if that is what initiates some fault. and go from there.

otherwise i am going to start believing that it is just a bad connection that just needed some wiggling to clean it up enough to make good contact again.

Well, another continuation of the last update. It has been acting absolutely perfect the last several times we have driven it. Multiple conditions. 2 hour round trip. In town idling. Rain.

Wondering if the connections were not great on the other module. And once it had a chance to sync up has been good. As it has only given me one code since I swapped it. And likewise the Tahoe has been absolutely perfect as normal also.



So I suppose as much as I don't want to, it's time to move to the next step and start using the remote start and see if it accepts up or not