Chevy Express Van Throttle Codes P1221, P1515 And P1516

I have a 2001 chevy express 3500 with an 8.1L engine. My problem is the SES light comes on along with the reduced engine power light and it can only go about 25 mph. I have had it to my local dealer and he is useless. I have had it to a couple of local mechanics with snap-on scanner. Current codes that come on when reduced engine power comes on are, P0404 EGR, P1220 ???, P1221 TPS, P1515 Fuel Pump Regulator and P1516 ???. The mechanic also told me there was some kind of reference to a G137 which he had no idea what it was. Here is what I have had done. Tune-up plugs & wires, fuel filter, fuel pump, fuel pressure regulator, EGR valve, oxygen sensors, TPS, throttle body, wiring harness to throttle body and a new battery. Can you help???

Answer:
Well, there isn't much left to change is there? Besides the EGR code, all the other codes are Throttle Position and/or Throttle body codes. G137 is just the name for a ground circuit, or Ground 137. You're probably in need of an Electronic Throttle Actuator Control Module, or TAC Module.

This unit is located in the upper left firewall area and is easy to change. Without seeing actual scanner results or parameters, this is just a guess, but since you've replaced nearly everything else, it's a good bet. One other possibility is a faulty accelerator pedal. There is a sensor built into it called the Accelerator Pedal Position Sensor and sends a signal to the TAC Module to open the throttle body as you depress the gas pedal. Either of these would have to be purchased at a GM dealer.

Thank you, for all you help. I have 2 follow up questions. I am trying to find a repair manual for my 2001 Chevy Express. The problem I am having is that all the manuals I find exclude my engine, the Vortex 8.1L. Do you have any suggestions? The second question is exactly where the "Electronic Throttle Actuator Control Module, or TAC Module" is located. My mechanic seems to think it is part of the Throttle Body. Do you have any input on this? Thanks

Answer:
I would have to say that since the 8.1L in this van is not very common, the non-factory manuals may not list it. You will probably need to get a set of factory manuals, if they are available. No, the throttle body is the "Throttle Actuator Control"(TAC). It is controlled by the TAC control module. It is located on the left side of the engine compartment, under the cowl. Sort of bolts up onto the cowl.

Question:
1998 Chevy Express Van. Codes P0131. Idles fine no power under load.

Answer:
Code P0131 is for low voltage on oxygen sensor. This should have nothing to do with the truck not accelerating. This could be the result of another problem. Have the fuel pressure checked and also check for a plugged catalytic converter. This can be done with a pressure gauge, or you can remove the exhaust pipe before the converter to see if that helps your truck accelerate.

I am back. I could not find a new TAC module a few months ago so I was able to locate a used one. After a few days I started having the problem again. I saved up some money and bought a new APPS (actually the whole gas pedal assembly. The only way chevy sold it.) Before I put it in today the van would start but reduced power light would come on when starting it. I put the new pedal assembly in and have the same problem. Can you think of anything that would be causing my problem with the reduced engine power?
 I would bet you have a problem with the used TAC module/throttle body. I would never recommend purchasing used electronic equipment for a vehicle. You should have it scanned and see what codes you have, I would bet they are for the throttle body/TAC.

The TAC module has been discontinued by GM/ACDELCO. How do you feel about re manufactured modules and can you recommend anyone?