"Reduced engine power"

hey guys. So I'm new here. I have a 2003 with a 5.3 Vin z. It's probably thw best running engine I've ever owned. But is has the dreaded p1516 p0120 p0220 which are all with the tac module throttle body and throttle pedal position. I've replace the tac, throttle body, tps on the pedal, cleaned the intake temp sensor replace the mass air sensor, and ran a ground wire from the throttle body to the ecm to tac and to the engine then to the body. Also cleaned the ground junctions at the lower driver's side body and behind the head. It still throws intermittent faults listed above while driving and goes into reduced engine power. I leave a scanner connected and clear the fault and it goes back to normal. Seems to do it alot more when it rains and it's cold outside. Lately it's been doing it at highway speeds. More often when idling. Anyone got any ideas? Pretty much only thing left is an engine harness which I believe is the issue. Thanks ahead of time.

have you replaced the pig tail pugs to everything tb related? they go bad.

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum, and other members will chime in.

Scottydoggs said:

have you replaced the pig tail pugs to everything tb related? they go bad.

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Hey thanks for the reply. No but I did re-pin the connectors on the throttle body and the tac module but like I said I believe it has a wire breaking down.

Find a wiring diagram and back probe the pins at the ECU and run temporary wires to the TAC/throttle body. See if that makes any difference.

You will basically have another set of wires in parallel, so if there's issue on the main harness, the temporary wires will prevent the intermittent loss of signal triggering the code.

If the problem goes away, then you know where the problem lies.

kayakfish247 said:

Hey thanks for the reply. No but I did re-pin the connectors on the throttle body and the tac module but like I said I believe it has a wire breaking down.

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As @ScottyBoy noted, the wires to (especially) the throttle body are prone to breaking underneath the insulation. If a careful inspection hasn't been done, suggest doing it from the TB back about a foot. You may not see a broken wire, so check them by flexing and by feel. A new pigtail might solve it. I think it was @89Suburban who cured his this way.

strutaeng said:

Find a wiring diagram and back probe the pins at the ECU and run temporary wires to the TAC/throttle body. See if that makes any difference.

You will basically have another set of wires in parallel, so if there's issue on the main harness, the temporary wires will prevent the intermittent loss of signal triggering the code.

If the problem goes away, then you know where the problem lies.

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That actually sounds like a good idea. Definitely try that. I actually have terminals I can use to run a new temp harness. Thanks

Thanks @Fless yeah my pigtail had been replaced by somebody and the connections took a crap so I re-soldered them and she has been fine since. Some pics here. Was a ***** to figure out I almost said hell with it and got rid of her.

Very common failure after the dreaded dead spot in the TPS position trace within the TPS. Then comes the Pigtail plugged into the TPS (They make a replacement that you just splice in) and then finally the harness that plugs into the the TAC Module itself. All 3 of these will cause the dreaded reduced engine power individually or collectively.

kayakfish247 said:

That actually sounds like a good idea. Definitely try that. I actually have terminals I can use to run a new temp harness. Thanks

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Afternoon. So I dug into this and removed the ground (black with white) off the pass side block. Re-grounded it to a good know ground but in the beginning I noticed when turning the key on the butterfly in the throttle body is fluttering and making a rattling noise with the engine off and also with the engine idling it make the same noise. Never noticed that before. I'm wondering if the actuator of the throttle body is faulty. Like I said it was a new throttle body replaced in August of 23. Anyone have an idea?