This is NOT a software issue! The aftermarket screens allow too much light into the proximity sensor.

**THE FIX**

Black electrical tape, cut two small holes with an exacto knife (about the size of a ballpoint pen) exactly large enough to fit over the two sensors. Cut out the holes so you now have a small rectangle with two holes.

Place the rectangle over the proximity sensors and the holes should line up.

Thats it!

Reconnect the "Faulty" screen and... VOILA!

I had the same issue.

My replacement glass doesn't have "that little piece that separates the ambient light and the prox". So i used the idea from Simon's method but instead of using electrical tape i used the black marker, painted on the glass similarly as it done on the original Apple glass. Did it several times so no light come through painted area. After that sensor's windows on replacement glass looks almost exactly as on original glass, and proximity sensor began to work.

I have an iphone repair store too.

I am having the same problem.

I have two different aftermarket glass supplier.

70% glass works on replacement. Some of them doesn't work. Then we use other suppliers glass or same suppliers glass. It works. We use Non working glass on another customer. It works most of the time.

It looks like software problem.

Once, none of the glasses didn't work on one of the customers iphone 4. After 4 replacement last try also didn't work. I was hopeless. I put my finger on it many times. No way. I put on my ear no way. I kept on my ear like 20 second. After 20 seconds it shot off. After that it started to working fine all the time.

Software. Software. Software.

What happens (I guess) when we replace the glass software trying to look for background reflections, brightness. Doing some statistics etc. etc.

Software. Software. Software.

Now replacing iphone 4 glass is nightmare nightmare nightmare.

Proximity problem solved.......

I just replaced yesterday one black iphone 4 broken glass. Proximity sensor didn't work. I was going to replace glass again. Before I replace the glass I decided to do a simple restore (4.3.3).

It worked ...............

Soooo it's not a hardware problem. It is software problem.

I guess : When you restore your iphone with a new firmware it measures your glass darkness and backgroud reflections while you restoring the new firmware. It also measures all hardware components. I am sure data kept in some files. When you replace the glass, new glass darkness and reflections are usually different from previous one (sometimes). You think your glass is bad. But your new glass works on other iphones. That explains everything.

If your proximity is not working --> You can simply restore your iphone to 4.3.3 (I just tested once and it worked with custom firmware 4.3.3 created by sn0wbreeze)

I hope it works for everbody.................

I have been working on this weird thing more than 2 months.

I use this fix works 90% of the time.

http://youtu.be/pTVPrxkNWhk

Also check if your still have tiny piece of foam strip btw the proximity sensors on the frame.

Some people said using black electrical tape works for them as well

How do you guys usually do it, when you are doing an lcd replacement, always use the scotch tape and black marker trick, or do you first replace the screen and then test if the proximity sensor works? And then if it not works, you have to do a re-assembly again?

We have a lot of repair shops that buy from us and I have heard all of these methods working on certain iPhones. I think it really depends on the iPhone. There is another method not mentioned here of the little lens that you put over the sensor before you install the new screen. We have them for less than $5 and they will fix the problem. I would try all of the free fixes first but if that doesnt work you can find the iPhone 4 Sensor repair lens here.

I too have had this same problem (3 screens, two different manufacturers, 3 proximity sensors, the two different model numbers) where the sensor just wouldn't work.

Tried restoring, didn't work.

SOLUTION: Black marker over area for sensors on underside of screen.

hi guys , This is NOT a software issue !!!!!!

Very easy Fix = first open your screen , this link = http://www.youtube.com/watch?v=iNM90pb-X...

then you can use a thin colored plastic layer, cut it to fit the sensor and glue it to the sensor , this image = http://www.iimmgg.com/image/0db8ed363bf3...

then replace your screen , this link = http://www.youtube.com/watch?v=E2r1sOML2...

Well Done .. its working 100 % tested on 3 iphons

I just ried the foam-fix with a DIY foam-frame.

It worked perfect on an iPhone we already assumed to be lost.

My guess:

If the light sensor gets too much light, it doesn't work (o'really :).

But where does it get the light from, when you cover the front?

From the backlight!

The light from the lcd panel diffuses into the light sensor.

So if you take a little bit foam to make a frame around the sensor - just like the thing on eBay linked above

http://tinyurl.com/6w7uutc

this problem is solved.

Wow.

see here, the proximity sensor lens might solve it

http://goo.gl/HlqcF

This may seem like an odd solution, but I recently found this image on a Chinese Parts Suppliers Website.

I have re-written message on image as original made little sense.

Personally I have not tested this as a verified fix, but to me it makes sense.

The sensor may be seeing the white surrounding it and is reading the sensor as open all the time.

Guys - the only thing you need for a working proximity sensor is a GOOD QUALITY glass, a working proximity sensor flex cable and the UV filter sticker. We sell the original iPhone 4 proximity UV filter sticker with the black foam from our online store

HERE

You don't need anything else - just those 3.

The most common fault is to lose the UV sticker during installation. Second most common is to use a cheap copy front with a poor light filter at the top.

I'd recommend fault finding in the order:

1) Check for UV sticker

2) Try new front glass

3) Try new proximity sensor flex

It should definetly be working by the end of step 3.

Also to add - on the inside of the phone (the other side of the proximity sensor) is a little black plastic block. this plastic block holds the proximity sensor towards the front of the phone. If this is not placed properly or is missing it can affect the proximity sensor. We also can supply this spacer block

HERE

I cut two pieces of black insulation tape with a small square hole in, one over each sensor with a little overlap, worked spot on. Next time I'll do this as a matter of course, I fit these a lot and it takes a bit of effort to do it twice! Lesson learnt

I would just like to add something as I have spent the best part of three days trying to sort through this one. I have tried all sorts of things from strips of insulating tape cut and placed over the sensor to colouring in the window on the glass. I couldn't work it out, each time I put the phone back together, the proximity sensor still didn't work.

Finally I worked it out and hopefully this will help other people as well.

We repair, refurbish and sell used iPhones http://www.reo-technology.co.uk and had come across this problem a few times in the early days of our business but recently, using better quality digitizers, we hadn't seen this for a while. I did however, as part of a promotional gimmick buy a pretty Blue front and back to customise a phone.

As I said, in the early days I had tried loads of different things, many suggested through this website and many others to try and work out this problem. Some say software issues, some say hardware. OK to clear this up, my logical guess it's a hardware problem that the software can't adjust to. It may well be that the clever software only works in a certain range, I'm not sure. What I do know is it's the sensor that can't cope with the variations on the different glass digitizer fronts. These vary from supplier to supplier, some work and some don't. During the many dismantling procedures in trying to get my customised blue phone to work, I tried one of my standard white digitizers and it worked perfectly so I knew it wasn't the sensor at fault. It's the quality of the window that lets Infrared light pass through it that can determine if it works or not.

Here is a simple diagram of how the sensor works:

The IR emitter sends out the signal and when you cheek or ear gets in the way it reflects back to the receiver and tells the screen to turn off.

I had tried all sorts and then I read an article about putting a little UV filter over the sensor and how it worked 100% so I decided to order one from eBay. When it arrived, it was much smaller than I imagined. When I looked closer, I realised this was already fitted to the iphone I was trying to get working. I had thought that I was buying some little add-on when in fact these are fitted in front of the receiver anyway. Now I really was confused.

Having stripped this phone down for the 6th time (the screws are starting to look a little worn out now), I though I'll stick this new little filter over the top of the old one. If this is what is recommended, I couldn't see that information clearly written down on any of the websites or anywhere on eBay where people are selling these. But as the phone was in bits, I thought I would try it. Below is some images to help understand what I am trying to explain.

As you can see from the pictures, it's quite small and only fits over the right bit of the sensor (which I assume is the receiver).

Top Left - Filter removed (This is standard as it leaves the factory)

Top Right - Filter fitted with extra filter to the right

Bottom Left - Filter

Bottom Right - Sensor with two filters fitted.

Bottom line is, this worked so now my iPhone with pretty blue front and back works as it should.

Okay, so we still get this problem sometimes.

We have like 200 pieces of the filter with the foam on it.

We saw some similar problems between the phones:

There are 5 different versions.

See the IMEI number (the first numbers)

0124, 0125, 0126, 0127, 0128

The strange thing, is that all versions have this UV filter with foam already installed, only the 0127 never has!

So @Chris, you say: Top Left - Filter removed (This is standard as it leaves the factory)

You're IMEI starts with 0127! Because other iPhone 4's always have this filter standard from factory!

Still have sometimes the problem after repair that the sensor is not working, when we just replace the complete flex with a new uv lens filter, it works 9 of the 10 times.

Wow lots of theories,

What about this problem,

The sensor didnt work anymore after a screen replacement. I replaced the sensor flex. No Result

Checked for the foam, it was still there, put a layer of tape on top of it. No Result

Replaced the OEM front with a original Apple from a working iPhone.

No Result.

Any ideas, this problem is so strange!

Thx u for all if no way u get success there us only obe way left change the sensior jec with heat gun

Add another masking tape and sharpie worked proponent. It takes some doing, but it works. I imagine foam or electrical tape will work as well, it appears to be about preventing the backlight from leaking onto the sensor.

Finally , I had to replace the sensor aswell as use the tapetrick. The one that worked for me was the one with scoth tape and a marker. tried all the other stuff here, but the tape stuff worked, and finally this is not a software issue, i tried the mainboard in an other phone , an the the proxi sensor and rest worked fine , and swapped back again, then it was just as bad. So that proves its not a software issue. Softwaregeeks ! Why i had to change the sensor was probably caused by the cracked screen. Took me all together at least 3 hrs. 2 different screens and a new prxsensor. (and some scoth tape.)

tried all the above,none worked,decided to take screen off, reassemble without screen,after this i connected screen externally,made a phone call and put finger over pair of sensors,still not working so the next step is to replace sensor cable.

UPDATE,

replaced flex cable, uv filter, foam surround used 2 one on top of other,genuine used but in excellent condition screen,

exactly the same useless,

Hello a few days ago I changed a flex cable because of the power button I also transferred the uv filter from the old cable/sensor to the new but it doesn't work the sensor is ok ( when I hold a cam on the phone while it is calling some number I can see the blue shine of the sensor)

The sensor next to the uv sensor has it also any filter??

Would a new filter be a solution to this problem???

I didn't try the tape or marker method , should I?

Would a iPhone 4s filter wok on 4 ???

Thank's to all of you guys!!!

I am totally more confused than b4. but i tried a very simple thing, I got a bit of pasta and stuck it up my nose , and it still doesn't work so fk it i aint eating pasta again

Hi, i'have replaced the power button-sensor flex.

After replacment sensor doesn't work.

I tried another flex. Not work.

I tried to change the glass. Not work.

Any ideas?

Yes. I have an idea:

Read the comments above. Alle of them. As soon as you tried everything mentioned here you can almost be sure your logicboard is broken.