Good advice on the opportunity to change out the coolant bypass hose.
When I got the P0330 code on my '99 Avalon, the diagnostic section of the shop manual offered a method to tell on which side of the EC1 connector--knock sensor side or computer side--the problem exists. Pins 3 & 4 of the connector are grounds for the shielding; pin 1, knock sensor bank 1 signal; pin 2, knock sensor bank 2 signal. Clear the P0330 code from the computer, use jumpers between the connector halves to swap pin 1 to pin 2 and pin 2 to pin 1, connect pins 3 & 4 together, then drive the car to 65-70 mph until the check engine light comes on again. Now, scan for the code again.
In my case, when the code changed to P0325 (knock sensor bank 1), it meant the problem was on the knock sensor side of the connector. If the code had stayed the same, P0330 in my case, the problem would have been on the computer side of the connector (pray this is not the case (if you believe in prayer

)).
At least, if you know the problem isn't under the manifold, you'll save yourself a lot of needless labor disassembling and reassembling, not to mention the expense (and they are expensive) of knock sensors and a shielded temperature-resistant wiring harness. However, if the problem is somewhere between the EC1 connector and the computer, inclusive, you'll need to check the wire between pin 1 of connector EC1 and pin 27 of the E6 connector (at the computer) or pin 2 and pin 28, depending which code you scanned. If those wires are good, your computer almost certainly will have to be replaced to eliminate the code.