Solutions for iPhone 6S retains signal under without SIM card

Fault Description: iPhone 6S retains signal after being removed SIM card

According to our ever experience, there may exist there following issues:

- Abnormal card holder

- Card detection pin problem

- Baseband Signal part problem

But we need to confirm it on this phone, let us start it.

Install the iPhone to test, we found that as the customer said, there is still a signal even if the SIM card was pulled out. According to previous maintenance experience, first we use FLUKE digital multimeter to check the resistance of each pin of the card base, especially the resistance of the card detection pin (that is, the card switch).

After measuring, it is found that the card detection pin has no resistance value. At the other end of the R3401, the resistance can be measured, and the fault is determined in the card detection pin, which is broken.

Solution: you can use jumper wire to connect directly to the card detection pin without removing the card holder.

Picture 1

Connect R3401 to the eighth pin of J3001.

The operation is shown under Trinocular Stereo Microscope as the following pictures:

Picture 2

After that, we reinstall it, test it and check it again, without SIM card, without signal, it is a normal one.