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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2601
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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2006 Isuzu npr. idles only, no throttle response.

Customer Question

2006 Isuzu npr. idles only, no throttle response. There is no voltage showing on either of the 2 wires that go to the Suction Control Valve. What do I need to check and repair to get this truck fixed?
Submitted: 5 years ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 5 years ago.
Hi I will help with your problem Please do not rate until all your questions are answered that way you wont have to pay twice Use reply to expert link.
Good morning,there are several different configurations on the trucks,it depends on were they were built for like USA or Europe.
Do you have a throttle cable?
The suction control you are talking about is it next to throttle linkage?
And do you know what that code say's, so I don't have to look up?{I have a idea just need clarification on what set up you have}.
Give me as much info as you think is relevant so I can give you the best answer.
Customer: replied 5 years ago.
Hi, and thank you, that all sounds great.
There is no throttle cable. it is a drive by wire system. The suction control valve (also called fuel pressure regulator) is attached to the side of the injector pump. The p0091 code says "Fuel Pressure Regulator Solenoid circuit open or short to earth". If I had a wiring schematic I was thinking of cutting the wire were it comes out of the ECM and wire a new wire directly to the fuel pressure regulator to determine if the wire/fuse is bad. Or also possibly trying a new ECM also.
Expert:  spankyjr1 replied 5 years ago.
Ok it is open because you have no voltage, not shorted. So you need to find what wire out of ECM powers it up.
Cutting the wire from ECM won't do you any good,you still need the 5 volt ref.signal to the solenoid and signal return.
Let me see if I can find a wire diagram,I just wanted to know what you were calling what, I thought you meant maybe fast Idle solenoid.
Know I know how to communicate with you. Some times people I talk to know nothing about system so if I said 1 thing they would not have a clue what I was talking about,but will be easier with you, because you have knowledge about how things work.
The one that is on injection pump is the air fuel ratio control valve, the regulator is on the return line or return side of fuel rail.
Anyway recheck voltage at sensor,to ground,one wire at a time you should have 5 volts to one wire,if you don't then we need to check at ECM,also you can just OHM out wire from sensor to ecm and check it that way to verify if it is the ECM.
Also it is throttle by wire, check voltage at throttle sensor, on throttle pedal,you can also do a sweep test on the pedal potentiometer.

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