Seeking your wisdom on the order of troubleshooting here.

2011 XF 5.0 S/C with 90K miles is throwing the following codes common on this forum:

• P0172 - Bank 1 rich
• P0175 - Bank 2 rich
• (Intermittent) P0101 - MAF Sensor circuit range/performance
  • After clearing the codes, P0172 and P0175 came back after a few short drives, but P0101 only reappeared a day later, accompanied by a violent bucking between 2,000 and 3,000 RPM.
• LTFT is about -5% on both banks at steady state
  • Car will go into Performance Restricted mode somewhere above 4K RPM when these codes are present, which I understand to be normal

Based on other threads here with this issue, it seems like the common wisdom is to clean and/or replace the two MAF sensors, then consider other possibilities. I plan to clean the MAF sensors shortly, but am hesitant to throw in new ones immediately given the following context (1) I have just had the the transmission completely rebuilt, and upon picking the car back up discovered that the parking assist features which formerly worked about 20% of the time now reliably engage when the car is in reverse, (2) when at warm idle (~590RPM), everything illuminated in the car pulses slightly, including screens, canopy light, and door lights, but the problem disappears with the slightest amount of gas, (3) the "alternator test" feature on my scanner which involves holding the engine at 2,000 RPM for 20s determined that the alternator output voltage was 14.69v, which I understand to be at the very upper limit of the safe acceptable range, (4) the previous owner put a nice chrome air intake on the rig and the Denso MAFs I see don't have the FoMoCo markings I have seen on OEM ebay MAFs for this car, which makes me think they were somewhat recently replaced.

The current troubleshooting ladder, testing the effect on each step is:

1. Clean MAF & run some cleaning fuel additives
2. Smoke test from intake
3. Replace MAF
4. Replace Battery
5. Investigate injectors & fuel rail

Given the other goings on here and the strange readings from the O2 sensor (which seem to sit at ~0.75 at idle but plunge to 0.01 under load), I'm starting to wonder if I shouldn't start heading in the electrical issue direction. I appreciate any thoughts y'all have.

 

Good Evening All,

I ended up replacing one of the MAF sensors, and this seemed to solve the issue for several days, and no additional codes popped up as even pending.

However, today the strange surging at light throttle reappeared, and the engine light came on again with a P0102 code -- voltage out of bounds.

Is it more likely the new MAF sensor is bad, the second un-replaced MAF sensor has since died, or that I have an underlying electrical issue?

Appreciate any thoughts, thanks.

 

Can you see the MAF voltages in real time with your code reader?

 

I can only see downstream O2 sensor voltages in realtime. I returned the cheap Chinese MAF sensor and replaced it with a remanufactured BSE unit. Cleared the codes, it cleared the permanent, and the car has run several cycles without throwing additional pending codes.

Comparing the pins of the Chinese unit to the remanufactured OEM, the pins seem a hair shorter and are definitely flatter, makes me wonder if the harness wasn't making good contact.