My 99 Altima's service Engine Light came on after I had my Transmission replaced and my engine cleaned(Front Main seal leak repaired) and it is showing code P1320. I can clear it, but it reappears. I've changed Plugs, Wires, Rotor and Distributor cap. Any suggestions?

There might be a TSB out on this issue. I would suggest having your dealer look it up and perform the repair procedure.

Classification: EC01-023
Reference: NTB01-059
Date: September 6, 2001

2000-01 Maxima; MIL "On" With DTC P1320 And/Or Spark Knock (Detonation) Due To Ignition Coil(S)

. First, try running premium unleaded gas, rather than regular, and see if the problem goes away.
. Second, see if the TSB or another applies to your situation.
. Third, determine what cylinder(s) the spark knock is coming from and replace coil.