Jump to content

Throttle Relearn

dewhite

Recommended Posts

dewhite Enthusiast

dewhite

Posted
Posted

So, I have been driving around with a MIL for code P0121 for a while (several months) and more recently it's been intermitently causing the Cruise Control not to operate (I think). This is on my 2007 Suburban 1500 w/ the 5.3L, with 110,000 miles which has been running fine and consuming no more fuel than I'm used to...

 

I read up on P0121 and saw that it involves the TPS integrated into my Throttle Body. I decided to clean to TB before spending ~$200 on a replacement.

 

I bought a can of CRC TB Cleaner at the parts store and spent about 45 removing, cleaning the port and paddle and replacing everything per the "remove/replace" instructions on alldatadiy.com I removed maybe .5 to 1mm of sticky carbon sludge from the bottom inside of the port. Is it normal to have this much crap in the top of the engine like this? I looked inside the (i guess it's called) plenum and saw sticky brown stuff all the way back...

 

After checking that the drive-by-wire was functioning with the key in "on" but without starting the engine, I replaced the intake assembly and proceeded with the Throttle Relearn procedure also found on alldatadiy.com Specifically, what I did was:

 

1. Remove negative battery cable for 20 minutes to reset all DTCs.

 

2. Start engine, run in park for 3 minutes

 

-MIL did not come on

-Engine starts at about 1200rpm, then slowly idles down to 800 rpm and back up to a steady 1000rpm

 

3. Remove key for 60 seconds

 

4. Start engine, run in park for 3 minutes

 

-Engine starts at 2000rpm, rises to 2500rpm, and oscillates between 2500rpm and 3000rpm

 

5. A few more cycles of 3. and 4. with the same results.

 

Is there anything else I can try before I have to pony up the cash to have a dealer hookup a tech II and perform a calibration?

 

THANKS IN ADVANCE for any ideas, suggestions, references, questions, etc!

redvett Senior Enthusiast

redvett

Posted
Posted

Removing the battery cable to clear codes causes the PCM to relearn fuel & timing tables. A perfect reason for not resetting the PCM. A 50-100 mile learning process is in order.

nickvrebel Senior Enthusiast

nickvrebel

Posted
Posted

It sounds like you have an air leak, go back and recheck the following:

1. check that the throttle body is reinstalled correctly and that the gasket appears to be resealed well to the intake manifold (as you called, "plenum").

2. check and recheck all connection of the intake tube - any leak of unmetered air will cause funny idle issues, the Mass Air Flow meter, located near the filter is what measures the air coming in to the engine.

desrtrat Senior Enthusiast

desrtrat

Posted
Posted

the gunk in your in your intake is from oil coming in through the PVC valve. best thing to do is run some Sea Foam through your intake. they have a new spray can with a nozzle that you put in through the TB and you spray down the inside. the nozzle is about 30" long. just follow the directions. if you keep getting a lot of oil in your intake you may want to look into installing a catch can in your PVC line..

 

good luck..

  • 2 weeks later...
dewhite Enthusiast

dewhite

Posted
  • Author
Posted

I just wanted to check back in, and say THANKS!

 

I rolled the truck out of the driveway and dropped it into gear at 2,500 RPM. Driving around for about 10 miles that night made an immediate improvement, lowering the idle in park to a much more managable 1,200 RPM. While driving, the idle was pretty normal, although downshifts came with a noticable surge, especially the 2-1 when coming to a complete stop.

 

Behavior continued to improve over the next several days, and after about 500 miles of driving has returned to what I would consider normal. It still takes about 60 seconds for the engine to settle down to around 600 RPM when I start it up, but that's probably just something I hadn't noticed before I started all this...

 

About the sludge in the engine - did you mean the PCV Valve? What would cause that much oil to creep up through the PCV valve? I remember that replacing that valve used to be a regular maintenance item, and that it was a cheap part and easy installation on my 2000 Silverado...

 

I've also noticed that the Cruise Control is still not working correctly all the time. It often will set and work as expected for as long as I'll use it (in excess of 100 mile stretches this weekend), but if I tap the brake, it may or may not work the next time I try to set it. Once it stops functioning it usually won't set for quite while, or until the truck has been shutdown and started again.

 

I figured that the Cruise Control was a direct result of the TPS reading out of range, but after 500 miles, the DTC still hasn't set itself again.

 

Anybody got any ideas? Again THANKS!

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Vu1can
      Seems to be Missing a lot of Updates

      By Vu1can · Posted

      So, GMCustomerService:  Judging by the Update History pictured above, is this truck missing any updates that it actually needs. If it's just for the infotainment system, the radio is working fine and no trouble with SeriusXM. and Android Auto is working fine wirelessly with my phone. Some months ago, an update notice was sent to my truck. I approved the update and it finished saying that the update was successful, but it seems that whatever that update was, it didn't actually get installed - at least not if I'm to go by the Update History shown above.   So, again, are there any updates that this truck really should have? I've checked with my dealer but they're reluctant or commit to anything and if I want them to check, they require a $200.00 fee just to check it out and then I'd have to pay for the actual update(s).    Ignorance is bliss, and if none of the updates goes to fixing any mechanical discrepancies, I'll just leave things as is.  
    • CNH-320
      Electrical Problem - solved

      By CNH-320 · Posted

      Hey everyone, I recently had an issue with my 07 2500HD GMT900. My DRL’s stay on at all times. Right front turn and right mirror turn signal indicator stay on solid at all times. By “at all times” I mean the only way to make them go off is disconnecting the battery. I tore the headlight assemblies out, tried disconnecting the harnesses to eliminate bad wiring at the harness, I unplugged the headlight switch, no change and the mirror turn signal still stayed on. My first thoughts were : Bad bulb and/or socket somewhere, under hood fuse panel bad, bcm bad, tail light or trailer wiring problem, or some random short to power in the harness.  Possibly a bad ground but unlikely. I had a big clue in the fuse panel, it had a burnt smell. I started pulling every fuse that had to do with DRL or right turn/park lamp. Nothing made the right directional turn off but pulling the DRL2 fuse made the DRL’s go out.  After studying wiring diagrams, I found that both problems had that fuse panel in common, the bcm also controls both problems but knowing the fuse panel had a burnt smell I removed and disassembled the fuse panel and found a little corrosion on the printed circuit board.  I ordered a new fuse panel from Amazon for like $260. When it arrived I installed it, and put everything back together, the problem was fixed. I figured the fuse panel needed to be replaced anyway so that was a logical place to start. Hopefully this story helps someone in the future. Regretfully I didn’t scan for codes before I did everything.
    • 2022LtTbZ71
      Service 4wd, ESC light, traction control light on, Service charging system (vehicle may stall)

      By 2022LtTbZ71 · Posted

      That stinks. I’m sitting on the side of the road right now with the same issue. Never had an issue before taking it in for the ground strap recall. Now I’m outside of warranty and they’ll probably want $200 just to diagnose what they already “fixed”. 
    • jagabom (Esquire)
      Passenger seat

      By jagabom (Esquire) · Posted

      I wonder kind of nuts and bolts they will come up with next? Jim
    • OnTheReel
      The Peckish Synapse

      By OnTheReel · Posted

      “It should be recognized, however, that there becomes a point where fuel economy oils do not make much economic sense for the end consumer—we talk about a fuel saving of ~€100 compared to a risk of €1000 Euros if the oil is too thin and causes increased engine wear rates. However, the benefit of these oils accrues to the car manufacturers. If their vehicles can save 1–2% fuel by using a special fuel economy lubricant, then that OEM can drastically reduce the amount of fines they need to pay.”   I liked this and the following paragraph as well but it’s really only touching the beginning of the benefits OEMs see from spec’ing these oils. After you factor in “out of warranty” service work and new car sales when these engines fail before their time, it’s a good racket for them. Just because you're paranoid doesn't mean they're not out to get you!

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...