lcdtest: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/lcdtest - from package: lcdtest

You may install the required package with command yum install {package}

Error in other languages:
lcdtest: bevel nie gevind nie
lcdtest: comandă negăsită
lcdtest: comando não encontrado
lcdtest: commande introuvable
lcdtest: command not found
lcdtest: käsku ei ole
lcdtest: không tìm thấy lệnh
lcdtest: komanda nerasta
lcdtest: Kommando nicht gefunden.
lcdtest: kommandot finns inte
lcdtest: komut yok
lcdtest: nie znaleziono polecenia
lcdtest: níor aimsíodh an t-ordú
lcdtest: no se encontró la orden
lcdtest: no s'ha trobat l'ordre
lcdtest: opdracht niet gevonden
lcdtest: parancs nem található
lcdtest: perintah tidak ditemukan
lcdtest: príkaz nenájdený
lcdtest: příkaz nenalezen
lcdtest: команда не найдена
lcdtest: командата не е открита
lcdtest: 命令找不到
lcdtest: コマンドが見つかりません