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Username Post: 1995 7.4 454 TBI CODES 35 AND 45        (Topic#374201)
Posts: 36

Reg: 03-08-22
12-21-23 04:48 PM - Post#2865120    

Hey everyone, I recently bought a 95 GMC c3500 hd with a 7.4l 454 TBI and nv4500. Truck runs GREAT initial startup. After it kicks down into low idle it will idle for a bit then rpms will go up and down and SES will pop up. The only codes I'm getting are dtc 35 and 45. I replaced cap and rotor and fuel filter. I checked fp at tb and key on engine off it jumped to 45 psi, dropped to 20 then went to around 25 psi. Cranked the engine and it went to 40 psi. Shut the engine off and psi instantly drops to 0. So I disconnected the fuel filter and put gauge at end of feed line. Key on is 50 PSI, key off is 49 and holds steady. Is this symptoms of bad fpr? My return line has a small leak that I will be fixing tomorrow. I also plugged the brick into it and O2 voltage says ---947 mv whether the O2 is plugged in or not. It doesn't change so I got an O2 sensor for it as well. Map is 1.34 volts running and 5.00 engine off key on. I pulled IAC and cleaned it, that made no difference. What is the solution to my issues? I figured ide throw an O2 and fpr at it. What's your thoughts??


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