Q: Engine goes to reduce engine power when headlights are turned on

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A couple of weeks ago, my Check Engine light came on. Mechanic checked it out, codes were. P0740 P085 P2761 U0107. So the told me to change the clutch which coat me $2000. I get the truck back. But that same night. The reduce power comes on. Since i had a code reader the only code that came up now was the U0107 code. The code reader did not remove thw check engine light when i pressed reset. Only when i turned off the headlights is when i could turn the check engine light off and get it out of Reduce Engine power. At night when i was stranded due to reduce engine power, i was able to drive it home with just fog lights, as soon as i tried to turn on the headlights, the truck will go to reduce engine power. First question, was this all a computer problem and i was ripped off by unnecessary transmission repair? 2nd is this a battery issue?

My car has 97000 miles.
My car has an automatic transmission.

Two of the original codes refer to the torque converter including control circuitry and devices, particularly a lock up solenoid. The only way to determine the circumstances surrounding the repair they performed is to have them show you the original diagnostic results (to condemn a part there will be documentary evidence in the form of instrument readings or scan tool results) or actually show you, and demonstrate, the defective component once removed from your car. In your circumstance, the "clutch" being referred to is within a sealed (welded shut) assembly, that is the torque converter. So, what they apparently replaced is the "torque converter" as an entire assembly, not "the" clutch. If they told you they replaced "the" clutch, they are not particularly informative or accurate. By the way, there is an access panel whereat you can glimpse the converter; if it were me, I’d be incredibly curious to peek in there and see if the converter was really changed out or not. The reason I mention that is the codes you supplied implicate other control components and not just the clutch. Some of these other components represent a less costly, simpler fix. At any rate, to answer your question, without having direct evidence it is hard to advise you as to whether or not you were taken. Going forward, by the way, you can minimize or eliminate that sort of problem by working one on one with "a" mechanic, as you would with YourMechanic professionals, because you can directly ask, "show me the evidence". These shops are huge bureaucracies and the notion that you are entitled to a reasonable account of what they are doing with your hard earned money is completely foreign to them. At any rate, the present code that reflects the reduced power issue typically is traced to a poor ground or electric power supply fault on specific CAN bus circuits. You can load test the battery and verify alternator output just in case, but it is likely a circuit trace will have to be performed to pinpoint the interruption on that CAN bus circuit(s). You need the Factory Service Manual wiring diagram to do that. If you want the required diagnostic steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a Check Engine Light diagnostic and the mechanic will resolve this promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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