If you didn't replace the knock sensor when you put the heads on, then it is now probably bad. Every shop and dealer I talked to all said to replace both the sensor and the wire. For some reason they fail after removing the heads, the dealer mentioned somethingh about the heat they are exposed to. You wouldn't think that the sensor would go bad just from removing the heads (unless when you remove the wire something inside the sensor breaks). The dealer mentioned that they would usually get the trucks back within a month after doing head work, if they didn't replace both the knock sensor and the wire.

If you test yours and it is bad, the cheapest place I found one was at Butler Toyota in Indianapolis(1-800-692-6396), it cost me 127.50 shipped to my door(no shipping charges on oreders over $100).<img src="/forums/images/graemlins/cheers.gif" alt="" />