E04 Error Can't watch or play

Step 1 Look at the camcorder's display to identify if it is in Safeguard Mode. If its display indicates an error number of E01 to E06, your camcorder is in Safeguard Mode.
Step 2 Disconnect your camcorder from its power source and remove its battery by sliding the latch forward and sliding the battery down while pulling it away from the camera's body. Wait at least two minutes before continuing.
Step 3 Remove the camera's cassette by pressing the "Eject" button, waiting for the cassette door to open, and lifting it out of the tape bay. This step is only necessary if the camera indicates the E03 or E04 error code or it tells you to eject and reinsert the tape.
Step 4 Replace the camera's battery, power connection and cassette, and turn the camera on.

Did you try removing batteries to see if it clears error?
this is first thing to do.

Error codes are indication that camera will require service. E04 is the only error you might be able to clear by holding down the eject button when placing battery back on camera.

E04 is the only one that a consumer can try to rid. This error normally is the fault of a bad tape. I recommend removing battery and HOLD DOWN EJECT, while reconnecting battery so its the first command camera sees. if tapes eject, try a new tape.

Here is some information regarding the E04 error message from http://www.techlore.com/article/10974/JVC-Camcorder-Stuck-in-Safe-Mode/:

"JVC notes that you are also given a malfunction code when the unit is placed into safeguard. If it displays code 01, 02, or 06 you should remove
the battery and powersupply and wait for a while. Code 03 and 04 indicate that you should eject and reinsert the tape.

If neither of these solutions work, your only alternative is to bring it to a shop or send it to JVC for diagnosis or repair. Unfortunately, there is no other way to clear the condition."

This doesn't seem uncommon, and indicates a bad tape is loaded, or unfortunately, that the camcorder requires servicing.

According to http://www.techlore.com/article/10974/JVC-Camcorder-Stuck-in-Safe-Mode/,

"JVC notes that you are also given a malfunction code when the unit is placed into safeguard. If it displays code 01, 02, or 06 you should remove
the battery and powersupply and wait for a while. Code 03 and 04 indicate that you should eject and reinsert the tape.

If neither of these solutions work, your only alternative is to bring it to a shop or send it to JVC for diagnosis or repair. Unfortunately, there is no other way to clear the condition."

If you are getting E03 or E04 errors on every tape you try, it sounds like a servicing is required.

An excerpt from http://www.techlore.com/article/10974/JVC-Camcorder-Stuck-in-Safe-Mode/:

"JVC notes that you are also given a malfunction code when the unit is placed into safeguard. If it displays code 01, 02, or 06 you should remove
the battery and powersupply and wait for a while. Code 03 and 04 indicate that you should eject and reinsert the tape.

If neither of these solutions work, your only alternative is to bring it to a shop or send it to JVC for diagnosis or repair. Unfortunately, there is no other way to clear the condition."

According to this, E04 denotes a problem with the recording media or the mechanical bits that deal with the tape. Hopefully trying another tape helps.

there was a hole under the tape deck.. u can try to force;y open it right there

Here's what i found. I was able to clear the message by opening and closing and ejecting the cassette. I also had to play with the battery at the same time. Keeping the cassette door open and then pulling out the battery. After is did this a couple of times i got the message to clear. I too haven't used my camcorder for some time and now that the error message has cleared the camcorder tells me that i need to clean the heads. Hope this helps. Below is the message i found that pointed me toward ejecting the cassette. An error indication (E03 or E04) appears. - (E03 or E04 UNIT IN SAFEGUARD MODE REMOVE AND REATTACH BATTERY) This massage a malfunction of some kind has occurred. In this case the camcorder's functions become unusable. - Eject the cassette once and re-insert it, then check if the indication clears. When it does, you can resume using the camcorder. If the indication remains, consult your nearest JVC dealer or service center

Here's what i found. I was able to clear the message by opening and closing and ejecting the cassette. I also had to play with the battery at the same time. Keeping the cassette door open and then pulling out the battery. After is did this a couple of times i got the message to clear. I too haven't used my camcorder for some time and now that the error message has cleared the camcorder tells me that i need to clean the heads. Hope this helps. Below is the message i found that pointed me toward ejecting the cassette. Good Luck, i'm off to buy a tape head cleaning cassette. An error indication (E03 or E04) appears. - (E03 or E04 UNIT IN SAFEGUARD MODE REMOVE AND REATTACH BATTERY) This massage a malfunction of some kind has occurred. In this case the camcorder's functions become unusable. - Eject the cassette once and re-insert it, then check if the indication clears. When it does, you can resume using the camcorder. If the indication remains, consult your nearest JVC dealer or service center