Chrysler Repair: 1994 Plymouth Voyager code 41, 12, plymouth voyager, powertrain control

Question
When I step on the gas the voltmeter goes down, below 12v if lights or fan are on.  When it goes back to idle it goes back to over 12v.  I replaced the alternator less than a year ago.  The battery is older but checks OK and has been starting the car in cold weather.

Answer
Hi Carl,
It sounds to me like your belt drive for the alternator is not tight enough and so the pulley and belt are slipping between one another. I would check the tension and make an adjustment to tighten that. Because you didn't mention the engine I can't tell you specifically what to adjust. If that doesn't prove to be the case, then I would check the dark green/orange field coil wire  to the alternator and verify its connection to the powertrain control module. Again that is plug-specific depending upon the engine. The 41 code that the voltage output is not as expected, which could be due to either possible cause. The 12 code is not relevant, unless the battery cables are not connected tightly or you have a loose ground on the - clamp to the body or engine.
Roland