throtle problem

[lysy1972]

Hi, I have drive by wire 2005 Frontier 4.0 I have pedal reading 100% and throtle 30% for some unknown reason,I swaped throtle body ... did not help,fuel pressure is 45-50psi constant.because of it truck does not want to downshift.No MIL for powertrain at all.Yesterday however I conected fuel gauge to fuel rail and placed it on the winshield to see if pressure drops and truck start to drive ok with full power downshift etc.I shut it off ones, then restarted it still was ok then I stopped second time and went to limp mode again.
Please if somebody had similar problem please advise
Thanx:bowdown:

[NissanTech]

I swaped throtle body ... did not help,fuel pressure is 45-50psi constant.because of it truck does not want to downshift.

The ECM does not controls the engine speed or gear with the fuel pressure. The fuel pressure should be constant.

The first thing you need to do is letting the ECM learn the position of the throttle body and pedal. The instruction to do it are in the "Engine Control" section of the service manual. You can download the section free from here: Knowledgebase - 2005 Frontier - Nissanhelp.com

The instructions start on page EC-720

[lysy1972]

I did this over the weekend truck drove ok fo 1/2 days and went back to same rutine,looks like if I release pressure from rail then it seems to drive ok for a while and then after few shut offs it goes bad again
Please advise

[tech22]

You stated that you swapped out the throttle body.Why did you do this in the first place? What was the issue that made you change it out? Were there any codes? After you changed out the throttle body did you preform the ECM throttle position relearn proceedure. If there were any codes did you clear the first? You were not very clear as to why you were working on the vehicle in the first place.

[lysy1972]

well I was suspecting problem with throtle body because throtle pedal was 100% and throtle only 30% NO CODES at all,truck did not want to shift down gears afte 35 MPH ten I did learning procedure for throtle and truck drove fine for 2 hr,after few shuts downs did the same thing again.:bowdown: