Hello DK friends,

I need your help! I have a customer with a 2005 Isuzu with a 4HK1 5.2L. The issue is that it loses power completely when the check engine light come on. I have IDSS hooked up and it showed that the throttle volts is cut and the motor is de-rated. Once I turn off the key and turn it back on the check engine lights goes off and for about 1-2 miles it comes back on again. Truck idle fine but when I give it gas no response. The other shop had replaced 4 injectors, fuel pressure sensor, and water /fuel separated filter and housing already. I have took out the fuel line from the pump to the tank and used the shop air to blow it back to the tank with the fuel cap open to make sure there was not restriction and also insert a clear fuel hose to make sure there is no air in the system. I also checked the fuel limiter and everything seem fine.

I have read on yahoo answer that some tech had the same issue and it came out to be the high pressure fuel supply pump. I am leading on that too but my customer already have over $2500.00 into this truck and the pump is $1500 new at my local dealer. Before replacing the supply pump I hope to someone here can share me their option.

Note: I have check with IDDS and the fuel pressure desire and actual is all in spec and the fuel regulator is also in spec, however after the check engine goes on the pressure desire is higher than the actual pressure. Also the throttle volt is 0 and not response. Seem like the ECM cutting off the fuel system.