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Discussion Starter · #1 ·
Hello everyone, I'm new to PlanetIsuzu.com

I've been trying to fix my Graandfather's Isuzu Trooper for the past 3 weeks with virtually no progress. I am going tell you guys everything i did so far. It started out with it not being able to idle. In diagnosing it I removed the TPS thats mounted on the throttle body. When I went to put it back on I put the tang in the wrong place and when the throttle motor ran It might have bent the tang. When I noticed that mistake I took it back off but the I couldn't get the tang on the TPS to mate up with the throttle body so I backed out the front adjustment screw on the throttle body to try to get it to line up. That didn't work, so i found a thin piece of metal to slide in and push the tang down to get it to line up. So I think I screwed up the throttle body adjustment basically. After I talked to the Isuzu Dealership they told me to check the Intake Manifold gaskets. I did, and they were bad. I replaced the Intake Manifold gasket set. I adjusted the screw on the throttle body so that I had about 0.015" of clearance between the throttle blade and the bore of the TB. (I read about the 0.015" clearance on here.) When I set it at 0.015" the screw is turned in further then what I think it was originally at due to the corrosion marks on the screw.

It will run fine for anywhere from a few days to a few minutes then it will go into reduced power mode and throw codes P1125 - APP System, P1295 - Electronic Throttle Control Power Manegement Mode, and P1515 - Command vs Actual Throttle Position Performance (PCM). We checked the wiring harness from the Acclerator Pedal to the PCM and from the PCM to the Throttle body. Everything had cotinuity. I cleaned the contacts behind the white cover on the TPS. I also replaced the PCV valve. I tried wiggling the harness while the motor was running but nothing happened when i did that.

So I am about ready to drop $150 a new throttle body unless someone can help me out.

It would also be awesome if someone can look at their trooper and tell me how much you have to move the throttle shaft back till it hits the stop.
 

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Basically, you have a problem where the commanded throttle valve position does not match the actual position as reported by the TPS and the air flow as measured by the MAP is not consistent the commanded throttle valve position. I think the TPS is not working correctly, but if you can buy a complete working throttle body for the right price that is probably the best course of action.
 

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Discussion Starter · #3 ·
Thanks for the info.

I was also able to upload a report from my scan too. Some of the freeze frame data looks ridiculous. The engine RPM = 16383 RPM, Vehicle Speed = 158 mph!

Could the ECM be screwed up?

The trooper was setting there idling when the reducer power light came on and the code was thrown.
 

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Discussion Starter · #5 ·
Well my scan tool seems to work ok on other vehicles.

I just ordered a new TPS form Advance Auto today. I am going to try that cause I think that the tang on the TPS might have gotten bent.

I am also going to pick up a can of MAF sensor cleaner and clean the MAF sensor.

After I install the new TPS i will set the screw back to where the corrosion marks on the threads put it.
 

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Discussion Starter · #6 ·
Ok i just wanted to give an update on the Trooper.

I replaced the TPS, cleaned the MAF sensor, and set the TB adjustment screw so it performed as a stop to prevent the TB blade from closing and sticking.

I could see that the tang was bent on the old TPS. That must have been causing the MAF to TP sensor correlation code. Which was causing the PCM to go into limp mode.

The bent TPS and misadjusted TB screw were causing all the problems. The Trooper has been running great for over a month now.
 
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