user23953: I know this problem is kinda common but I had to post it anyway.
Before anything, I would like to inform you guys that I changed the fuse of my Arduino Pro 3v3 @ 8MHz to allow 1.8 V brownout and also programmed CKDIV8 AND CLKOUT. In other words, the fuse configuration is this: E:FE, H:DA, L:3F.
The programmer is the Arduino 2009 running as ISP programmer. The target is Arduino Pro Mini 3V3 @ 8Mhz.
I also used a 0.1uF cap between reset and ground in the Arduino programmer.
After a good time using the Arduino Pro without problems, some random problems began to appear when I tried to upload a program with the programmer (Arduino as ISP). So I tried to burn the bootloader again and the following message appeared ""avrdude: Yikes! Invalid device signature."
The same occurs when I try to communicate with avrdude using this command "avrdude -c arduino -p m328p -P COM3 -b 19200 -v".
Some tests I did:

Continuity test directly at uC pins between those signals: SCK, MISO, MOSI, (/SS - /RESET). No problem good connection.
Verified the clock in XTAL1 and XTAL2. No problem 8MHz.
Verified the clock in CKOUT (Arduino Pro pin 2) and measured 1MHz.
I also tried to delay the avrdude using -B5, B10 and another values. With a quick search on Google some people are saying that those delays don't work with the Arduino as ISP.
I used some sketches for slow clocks, which I don't remember, and no luck.
External power and no luck again.

What am I missing? Do I need to change something to communicate with Arduino Pro running at 1MHz?

user10794: If you are burning the bootloader through the IDE it won't expect the CKDIV8 fuse to be set.
I have a bootloader programmer which you could use to reprogram the bootloader. You just need another Arduino (eg. Uno, Mega) and connect 6 wires between each of them like this:

The sketch for programming the bootloader is available on Github:
https://github.com/nickgammon/arduino_sketches
You want the one in the "Atmega_Board_Programmer" subdirectory.

23953: <p>I know this problem is kinda common but I had to post it anyway.</p>

<p>Before anything, I would like to inform you guys that I changed the fuse of my Arduino Pro 3v3 @ 8MHz to allow 1.8 V brownout and also programmed CKDIV8 AND CLKOUT. In other words, the fuse configuration is this: E:FE, H:DA, L:3F.</p>

<p>The programmer is the Arduino 2009 running as ISP programmer. The target is Arduino Pro Mini 3V3 @ 8Mhz.</p>

<p>I also used a 0.1uF cap between reset and ground in the Arduino programmer.</p>

<p>After a good time using the Arduino Pro without problems, some random problems began to appear when I tried to upload a program with the programmer (Arduino as ISP). So I tried to burn the bootloader again and the following message appeared ""avrdude: Yikes! Invalid device signature."</p>

<p>The same occurs when I try to communicate with avrdude using this command "avrdude -c arduino -p m328p -P COM3 -b 19200 -v".</p>

<p>Some tests I did:</p>

<ul>
<li><p>Continuity test directly at uC pins between those signals: SCK, MISO, MOSI, (/SS - /RESET). No problem good connection.</p></li>
<li><p>Verified the clock in XTAL1 and XTAL2. No problem 8MHz.</p></li>
<li><p>Verified the clock in CKOUT (Arduino Pro pin 2) and measured 1MHz.</p></li>
<li><p>I also tried to delay the avrdude using -B5, B10 and another values. With a quick search on Google some people are saying that those delays don't work with the Arduino as ISP.</p></li>
<li><p>I used some sketches for slow clocks, which I don't remember, and no luck.</p></li>
<li><p>External power and no luck again.</p></li>
</ul>

<p>What am I missing? Do I need to change something to communicate with Arduino Pro running at 1MHz?</p>
 10794: <p>If you are burning the bootloader through the IDE it won't expect the CKDIV8 fuse to be set.</p>

<p>I have a <a href="http://www.gammon.com.au/forum/?id=11635" rel="nofollow noreferrer">bootloader programmer</a> which you could use to reprogram the bootloader. You just need another Arduino (eg. Uno, Mega) and connect 6 wires between each of them like this:</p>

<p><a href="https://i.stack.imgur.com/NUmcF.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NUmcF.jpg" alt="Program bootloader"></a></p>

<p>The sketch for programming the bootloader is available on Github:</p>

<p><a href="https://github.com/nickgammon/arduino_sketches" rel="nofollow noreferrer">https://github.com/nickgammon/arduino_sketches</a></p>

<p>You want the one in the "Atmega_Board_Programmer" subdirectory.</p>
