Isuzu Repair: 2004 P1239 code, autozone, voltage regulator

Question
my 2004 Rodeo's 'Check Engine Light' has intermittently been coming on, storing code P1239. sometimes the 'Reduced Power' light comes on with it but quickly goes out when i feed in some throttle (either in neutral or driving). no other issues have been observed. at one instance of the 'Check Engine Light' coming on i shut down the engine and when i restarted it 2 hours later the light was off. i then put 550 miles on without any lights. the next day i started the engine, no lights on, but when i stopped to get some coffee i let the engine idle for 3 minutes (in neutral) and when i returned both lights were on. as soon as i pressed the throttle (in neutral) the 'Reduced Power' light went out. a friend read the code and again the only one was P1239. he cleared the code and 10 to twelve engine cycles later it has yet to reappear (no extended idle, though).

Answer
I would be guessing that the voltage regulator might have something to do with it John. I would go to Autozone and have them check scan and diagnose your vehicle. And the bonus is they do it for free:) Although I am still searching for a better answer as well.