2019 Pathfinder MAF sensor issues

Central FL
Yup, a mis-fitting air filter can clog a platinum wire MAF fast. It goes through a cycle where it will heat the platinum wires beside the thermal sensors, periodically to incinerate any contaminants. Most of the time it just mildly heats and monitors the air stream temperature fluctuations to calculate for relative air flow rate. Over time, any cruddies that collect will coat over the platinum wires for the heater element part of the sensor and those will give you your lean codes... but *not* trigger a circuit code malfunction.

In my limited experience with Nissan:

A code failure for the circuit usually means 3 things to check in order of expense.

1) The sensor itself is contaminated as stated above. CRC MAF cleaner does work a trick for these. Once the sensor is removed, there will be a visible wire from the side. Looking longitudinally at it from the opposite side from the plug, they're are two "ports", one longer than the other. Blast the visible wire with cleaner, then hose out the two ports, back and forth until satisfied. Wait for it to dry for a few minutes and reinstall.

2) Sensor plug &/or wiring issues. Inspect the socket and plug at the sensor for missing or crushed weather pack. Use electrical contact cleaner and a tooth brush to remove any old green or white crusties on the electrical contracts. Gently probe the weather pack to re-seat it with a pick or a pocket screwdriver. Give it just a taste of silicon spray lube before reassembly (on the weather pack only) and hope for the best.

3) And this one sucks the worst... it will be either a bad ECU box or ECU system grounds. On my Nissan, I had similar symptoms as yours. MAF clean and then replace did not resolve it. What did it? Bad grounds. Luckily my ECU was in good shape, but it's chassis grounds weren't. Had to disassemble and tilt the dash on my Murano. There are two ground studs my ECU is affixed to, and after years of a leaky moonroof, they were just rotten. Cleaning them after blasting out the moonroof drain tubes, affixing them with new hardware, a shot of rust covering paint...all was good again. It's painful getting in there though. And luckily in my case the ECU was fantastic, but lost contact with ground.

Nissan run great. When they're running great. ;>
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