2003 GMC Truck

2003 GMC Truck 6 cyl Four Wheel Drive Automatic 135000 miles

Three days ago I was driving at nearly 60km/h and the truch lost power. The more I press the accelerator the louder becomes the engine sound, as if there was a lion inside. I shifted the gear manually to 1st gear. it gave me the SES and Reduced engine power lights. I scanned the PCM and the trouble code was P1514. Actron scanner explained it as TB problem. So I purchased a new one and installed it, but a new problem occured. Before, it used to produce the sound. Now, it produces the sound in addition to cutting of and running regularly and continuously as long as I keep pressing the pedal. The pedal is 7 months old, O2 sensors, TB, fan clutch, all new. The sound is like the TB is open wide but no fuel to accelerate the engine. At nuetral, the engine runs normally. It happens only when I accelerate, and it dies out when warm.
Can it be the MAP?
The scanner read as follows:
MAP KPA = 100 While Ignition switch =ON
MAP KPA = 35 While the engine is running

Can it be the fuel pump?
How can I check the pressure of the fuel pump without tools?
I saw a valve on the fuel line. Is it the check pressure valve? (Picture)
Can it be the fuel regulator? How does it function & what does it do?

March 7, 2009.

The line you are seeing is an evap test port, its for testing evap sys on this vehicle. Has nothing to do with fuel pressure. Try following this info first, A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.

The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit. Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded. If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. Post back with what you find.

Brian 1
Mar 7, 2009.
OK. This is about the throttle valve. What about the pictures above? What's that valve for?

Mar 7, 2009.
Do you mean the one you have circled? Its an evap test port, has nothing to do with the fuel pressure. Follow the info I posted and you should be ok. Post back with any oter questions.

Brian 1
Mar 8, 2009.