Reduced Engine Power

[tomloans]

Over the years, I had to solve this problem and in fact I have for the most part. Every 1000 miles or so, out of nowhere, it goes off. Then I can just shut it down and it is fine again for many miles. Question is for the amazing knowledge base from amazing people here, how do you disconnect this nuance feature? Has anyone figured this out?

 

[OR VietVet]

CEL? Solve problem how? Just by shutting off? Shut off for how long? Age and quality of tune related components? New tune components ever make a difference?
What year and make and engine size we dealing with? Disconnect this nuance feature? Are you saying it goes to "limp in mode"?

 

[tomloans]

It is 5.3 non flex engine 2003 Tahoe. Yes "disconnect the nuance feature" that cause the "limp mode" or the "Reduce Engine Power" ( max 1500 rpm )

 

[OR VietVet]

So...any codes?

 

[tomloans]

Yes the usual p2135 or p1516 and one other I can't remember.. I have changed out the trhrottle position sensor at the gas pedal and have changed out the throttle body. I have changed out the wiring harness as well and cleaned and tightened up the grounds under the drivers seat on the frame and behind the engine. It was good for about 3 years and then now I am starting to get it again every 500 to 1000 miles. Oddly enough both of my vehicles are doing the very same thing.

 

[Jonesy92]

My reduced engine power threw codes for lean conditions on both banks, until I got a fuel gauge I also didn’t know that I was only running 17lbs At the rail.
Intake gaskets are a common thing(Current ‘03 Tahoe 5.3, Non flex owner),and should be checked. Ground issues are another big thing. Search the forums if you haven’t already.

 

[live2pull]

Yes the usual p2135 or p1516 and one other I can't remember.. I have changed out the trhrottle position sensor at the gas pedal and have changed out the throttle body. I have changed out the wiring harness as well and cleaned and tightened up the grounds under the drivers seat on the frame and behind the engine. It was good for about 3 years and then now I am starting to get it again every 500 to 1000 miles. Oddly enough both of my vehicles are doing the very same thing.

Did you use an AC Delco professional throttle body? Not just the throttle position sensor? I had these exact same issues and the only fix after lots of trouble shooting and parts throwing was an ACDelco professional throttle body.

 

[OR VietVet]

I also used Genuine GM or AC Delco parts when doing my new throttle body

 

[Matthew Jeschke]

I would not disable "limp mode". It's either falsely tripping OR getting invoked for an underlying issue that could damage the vehicle.

Sounds like you got your lean issue straightened out. I was going to say grounds as well. You could also have a fault in the harness for the throttle cable. Check continuity, wiggle harness as well while doing it. I don't have the wiring diagram. I believe the throttle control stuff runs straight back into the PCM. You want to check the whole span of the signal wire. I typically pull the connector off the PCM and find the pin to do it that way. You can also if you want to save some time, poke a small probe (needle) into the wire near the PCM. Then patch back up with liquid tape glue when done.

My two cents.

 

[rockola1971]

Could be in the TAC module or dead spot on the DBW pedal pot or associated wire problem of either. Also check for corrosion at TAC module plug, DBW at Throttle Pot plug or even at the PCM wire connectors.
P2135 points to either the throttle position sensor at the throttle body OR the one at the throttle pedal. They are not in agreement with respect to position (output feedback voltage). You might be able to catch a dead spot on the throttle pedal with a decent scanner. I use the Tech 2 clone for testing this.

 

[iamdub]

It is 5.3 non flex engine 2003 Tahoe. Yes "disconnect the nuance feature" that cause the "limp mode" or the "Reduce Engine Power" ( max 1500 rpm )

2003 is a changeover year- do you have DBW (Drive By Wire) or DBC (Drive By Cable) throttle body? If DBW, a scanner that'd show live data and capture a freeze frame when a code is set would be really helpful.

*EDIT* After looking up the two DTCs you posted, I'm sure you have DBW. Get a scanner and watch the TAC (Throttle Actuator Control) signals compared to the TPS positions. Example: TAC commanded 50% throttle, TPS reported 35%. Could be a very short-lived loss of coms, which could be a faulty wire in the system or a failing TAC module.

 

[Doubeleive]

2003 is a changeover year- do you have DBW (Drive By Wire) or DBC (Drive By Cable) throttle body? If DBW, a scanner that'd show live data and capture a freeze frame when a code is set would be really helpful.

*EDIT* After looking up the two DTCs you posted, I'm sure you have DBW. Get a scanner and watch the TAC (Throttle Actuator Control) signals compared to the TPS positions. Example: TAC commanded 50% throttle, TPS reported 35%. Could be a very short-lived loss of coms, which could be a faulty wire in the system or a failing TAC module.

I wish these were all still drive by cable I hate the freaking lag and the stupid traction control, I know how to drive I don't need a computer telling me how to do it.

 

[rockola1971]

I wish these were all still drive by cable I hate the freaking lag and the stupid traction control, I know how to drive I don't need a computer telling me how to do it.

That computer isnt there for you! I cant imagine you run into too much "fun" in California. That computer is there for those geniuses in Oklahoma that havent the slightest clue how to drive in "winter weather". Keep in mind they shut the town down when they get a 1/2" of snow. Now here in the true midwest (think IL, IN, MO, MI, WI, OH) that computer is there for all the geniuses that believe they can drive in 8" of snow and a whiteout happening or 1/2" of ice in 2hrs. The same geniuses that have put their vehicle in a ditch or up against something else that wasnt moving...atleast 3 times in their life.

 

[iamdub]

I wish these were all still drive by cable I hate the freaking lag and the stupid traction control

That's what tuning is for!

I know how to drive I don't need a computer telling me how to do it.

The CDT would beg to differ.

 

[tomloans]

I have to agree with IAMDUB. Not easy to drive any of these vehicles without traction control ( for that matter why bother ). I think some would be very surprised how quickly you can lose control without traction control. Personally I would rather have it and not worry. I know of one who thought they could handle it and lost it around a corner and have rolled down an embankment once they disengaged it. I recall one time, driving in cold weather that it engaged over some ice I didn't see - it was fortunate because I could have been in a serious accident. For sure on high performance vehicles, transaction control is critical for safety, even for those who believe they can drive without. Be careful. Over confidence can cost you your life.