Engine check light

[AussieIsuzuRA2004]

Hi all this is my first post as a new member,
I have a tech question for anyone with an answer regarding my 2004 Isuzu rodeo itd 3.0.RA 4x4.
I recently had the engine check light come on while driving around which placed my motor into limp mode..
I pulled over into the break down lane and killed the motor. Waited 5 mins or so and started the RA Again. The check light went off and normal operation returned so I drove home.
few weeks past with normal operation but slowly the fault light returned

I have scanned the CPU and produced the fault code P1120E this led me to the Throttle Position Senser, I have replaced the Senser but an haveing trouble calibrating the new Senser properl. The fault light is basically on all the time...!
If anyone has the specs for the TPS calibration at idle that would be a great help and I could rule out the TPS as the problem. The EGR is the next target and then the turbo boost Senser.
Thanks in advance

[AussieIsuzuRA2004]

Hey everyone, im still no closer to understanding my problem with my engine check light, i removed the EGR to clean it but found it to be very clean and with gasgets in perfect condition, i reinstalled EGR today continued to test. while the engine was warm i took the truck for another test drive and as uaual the engine check light came on 1.5 kms down the road and i limped the truck home. Leaving the truck on i Tryed to reset the cpu and clear the codes (from the advise from utube) I popped the bonet to disconnect the negetive terminal from the battery but as soon as i touched the terminal when loosening the engin checklight went off and the reves dropped to mormal rpm round 850. i was left scratching my head thinking that this was new and Maybe its fixed so i drove the truck again but sure enough the check engine light came on again after 1.5 kms and i limped the truck home once again feeling more comfised them ever.
Can you guys please help me if you can..

[AussieIsuzuRA2004]

in light of recent post i was wondering if you anyone has the engine manual for my 4JH1TC. If so could you send me a link or message thank you.

[stardog]

I don't know if anybody has a manual on that engine here but I have seen the work shop manuals on eBay for sale on cd for $5-$7.
I just goggled ra rodeo and came straight up this might help you out.

[geeves]

http://www.mediafire.com/view/b3e4id89dco831k/Dmax.pdf

this should help

[geeves]

http://www.mediafire.com/view/b3e4id89dco831k/Dmax.pdf

this should help

[stardog]

There is a big write up on 4wd action site about this problem with the 4jh1 engine didn't read it all but seems a common problem with them.

[AussieIsuzuRA2004]

Thank you Stardog and geeves for your reply, i will look it all up and hope it is the start i need, cheers once again, ill be in touch.

[AussieIsuzuRA2004]

Well after a lengthy read from my workshop manual and an OBD2 Bluetooth purchas and a digital volt meter, I am pleased to say that the fault light problem has been fixed.

I had purchased a new TPS from eBay WA Aust. And installed it before I had received the odb2 and tried to adjust the position, it soon became apparent to me that this adjustment is almost impossible to do without the obd2 scanner.when the obd2 - ELM 327 arrived, (its just a cheap scanner for android $16.50) I had some trouble pairing the device to the android phone using the App "Torque" lite. This was Awesome to see the real time info of the engine. But the fault code finder did not pick up the engine check light that I was hoping it would it simply said no faults detected .
This was also puzzling as the engine check light was clearly visible on the dash board.... Frustrated but not detoured I pressed on reading the live diagnostics and found that the TPS was reading 28% at idle. I thought to myself that this should not be the case and started reading the manual again and found that the throttle possition should be reading 0% at idle and that the idle speed should be set to 800rpm with the air on off.
Armed with this new information I set off to investigate if there was a differentce between the old TPS and the new WA TPS. Setting the DVM to ohms I charted the difference in resistance between the two TPS and did find that they were out by 0.50 ohms at starting position and even greater at wide open.
This led me to think two things,
1) the new TPS was the wrong one.
2) maybe the original TPS was ok but just in the wrong position and needed to be calibrated.
Removing to new TPS and replacing it with the old one I only nipped up the locking screws and hooked up the Bluetooth ELM 327 to the Obd2 port and ran the app, I then adjusted the TPS down by softly tapping it while watching the On Boards Diagnositics on the android device until It reached 0% on the Throttle position which also meant that the idle speed was exactly to spec at 800 rpm I then tightened the TPS screws.

I have now been driving the Rodeo now for two weeks with not even hint of a problem.
In summary I can say that the reason the fault code P 1120 E came on was that the TPS and the idle speed sensor were both sending a signal to the CPU and that was the reason the CPU was making the engine go into lump mode.
I would like the thank Stardog and geeves for their advise which lead me to fix this drawn out problem and I hope this well help others.
Peace to all and thanks for reading.

[stardog]

Glad to hear you got it sorted out and has been problem free when running now.
Cheers stardog