P1320 codes are most often set by an ignition coil failure on VQ-series engines. If you are lucky, it will also show a P0301-P0306 code, or codes, to identify the cylinder on which the coil is failing. Hanshin made coils or more likely to fail than the Mitsubushi made units. If you don't have a cylinder misfire code, it can make it difficult to identify. Many simply replace all 6 coils, which can get expensive at roughly $75 each. When I worked for Nissan, tech support would suggest replacing one bank of coils and see what happens; if the code came back, one would replace the other bank. At least that way there's a 50/50 chance that you'll only have to replace 3 coils instead of 6. You can do a resistance check on each coil, but those tests don't always confirm a bad coil. Often these coils need to get hot before they fail.