Check this out, I had a code 34 for the egr valve I replaced the egr valve and sensor, reset the timing and also released the code for the egr valve by disconnecting the main lead. My timing was off and I had it reset every time it is reset it ends up changing itself. How does this happen and why? Also what is a knock sensor and what purpose does it serve.
When you check or adjust timing there is 1 wire that you disconnect at the distributor. This is to adjust the initial timing. Once that wire is reconnected the computer will adjust timing based on different sensor inputs.
Basically a knock sensor detects detonation and signals the computer to retard timing. The are very sensitive to installation torque. They cannot function properly if the installed too loose or too tight.