pwhich: 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/pwhich - from package: perl-File-Which

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

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