As automotive technology moves forward, ignition systems are becoming more and more entangled with other systems on the engine. The current generation Nissan Maxima 3.5L V6, which was introduced in 2004, has a fairly conventional coil-on-plug (COP) ignition system. The individual coils are driven by the powertrain control module (PCM) using the input signal from the crankshaft position (CKP) sensor as the primary timing trigger. But what makes this system different from others you may be familiar with is that the PCM also uses input signals from the two camshaft position (CMP) sensors (one for each cylinder bank) to modify spark timing. Nissan also refers to the camshaft position sensors as "PHASE" sensors (for cam phasing, I assume).

Spark timing on the 3.5L engine is nonadjustable and is controlled by the computer. You can read the timing on a scan tool, or if you prefer to do things the old fashioned way, you can actually check the spark timing on this engine with a timing light. The catch is you first have to remove the #1 COP ignition coil (the first cylinder on the rear bank) and insert a plug wire between the coil and spark plug. Then you can clamp your inductive pickup onto the plug wire and observe the timing marks on the crankshaft pulley. The timing spec for this engine is 15° plus or minus 5° BTDC (Before Top Dead Center). The idle spark timing can vary quite a bit depending on what the PCM thinks the en...