5V charging through ATX PSU?
shorting D+ and D- indicates to the PD (portable device) that it is connected to a DCP (downstream charging port) and is allowed to draw up to 1.5A. It's all in the USB Battery Charging spec (google BC1.2). What are you doing with the 1k resistor? Are you using your multimeter correctly (in series with the circuit). What do you mean by "my phone shows"? Forget your phone, the multimeter shows the truth. Also know that your phone will draw a different amount of current depending on where it is in the charging cycle.