Low Beam issue

The gen6 Altimas don't have fuses, they have P-MOSFET transistors in the IPDM (Nissan calls them "Smart FETs"). The FET's will quit working if a short or overload is detected, then reset when the problem is resolved. However, you only get 50 detections in a row and then the IPDM is permanently screwed. The first thing to do is put a test lamp across the bulb connector terminals with the bulb removed, if that lights then you have a connector problem. If it doesn't, check from the low beam wire to a chassis ground, if that lights then the ground wire is broken. If that doesn't light, then start tracing back toward the IPDM.

PowerslavePA said:

The count is wrong. The fifth attempt to operate the headlights advances the retry counter by 1. Eventually, this counter could reach 20, which means the IPDM has recorded 100 retries (20 times 5). If the retry counter hits 20, it bumps the circuit malfunction reading from 0 to 1. Now the system permanently shuts off the power supply to the failing circuit; for example, it’s the headlights. If this happens, there’s no way to reset the IPDM with a scan tool or other procedure. Instead, you must repair the circuit and replace the IPDM.

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That's all correct, I misremembered the count. However, to avoid chasing one's tail, do put a test lamp on the headlight connector first. The vast majority of one-bulb-out issues turn out be poor pin or bulb connections or broken wires, usually right at the connector. Checking with an independent test bulb at the headlight connector tells you immediately what part of the circuit the problem is in, and you can chase it up or downstream from there as needed.

It would have been more helpful if Nissan had put LED indicators on the IPDM to show the condition of the SmartFET's, but I suppose it wasn't cost effective. Very few scanners will read the IPDM, so the DTC's it throws when the FET's are shorted are pretty much useless to the average DIYer.