2000 jimmy p0122 again.. help

Ok.. I have a 2000 jimmy SLE, 4.3. Started running rough and died. Read the codes... p0122 was there. Checked the voltage and instead of 5v constant it was fluctuating never reaching 5v... so checked at the ECM and the grey wires comming form that were all fluctuating also.
Took it to the shop and they got it running... 2 weeks later and $250.00 back again. p0122. Is this an electrical issue and where do I look?

The code is for low voltage in the TPS circuit.

Was TPS sensor replaced?
What all did they do on the 250$ bill?

Yes.. I replaced the TPS and wasn't the problem.
They hooked up to the ECU and made it re-learn everything and changed the distributor cap and rotor button. Also my head lights pulse as the truck runs and don't get brighter with acceleration... just pulse steady.

You have a voltage problem.
Could be caused by bad connection or bad wiring or even bad battery or alt or PCM.
If head light flicker that is a good place to start.
Get a good volt/ohm meter out and start check voltage from battery to pcm and alternator.
And do not forget the grounds.

Ok I just bought a real good meter so i'll start testing... thanks