2014 Mitsubishi Diagnosed with P0171, P0142, P0108, P0102, P0113 Codes and Air Flow Issues

You’ve got an engine drivability / fuel control mess going on. Working hypothesis: MAF/MAP signal and/or wiring issue causing the ECM to lose its mind on air‑metering, which then throws fuel trims off and confuses the O2. Runner‑up is a big unmetered air leak (vacuum/intake) plus a weak MAF. The scan data pattern will separate those two.

Codes you listed:

• P0171 – system too lean bank 1
• P0142 – O2 sensor circuit (usually bank 1 sensor 1)
• P0108 – MAP sensor circuit high
• P0102 – MAF circuit low
• P0113 – IAT circuit high (IAT usually built into MAF)

MAF reading 4.78 g/s at idle and LTFT +12.5% both banks says the ECU thinks it’s not getting enough fuel for the air it thinks is there.

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Most likely culprits

• Bad MAF / IAT signal or wiring (P0102, P0113) – Low MAF and high IAT voltage together scream sensor or connector issue more than a simple vacuum leak.
• MAP sensor or its circuit (P0108) – High MAP signal (voltage) will make the ECU think load is wrong, fighting with the MAF and skewing fueling.
• Unmetered air leak (vacuum/intake leak) – Would explain lean trims on both banks; if big enough, it can also make the MAF reading look “low for reality.”

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How to narrow it down

1. Confirm engine / setup

   • Tell me: exact engine (e.g. 2.0, 2.4, 3.0, etc.) and whether it’s stock intake or aftermarket.
   • Idle RPM in park and whether it idles smooth or hunts.
   • This matters because “normal” MAF g/s depends on engine size.

2. Basic visual and wiggle test

   • With key off, pull the MAF/IAT connector and MAP connector.
   • Look for: green corrosion, spread pins, broken locks, oil in connector, rubbed‑through harness near airbox/throttle.
   • Plug back in, engine idling, wiggle the harness.
   • If idle stumbles or MAF/IAT/MAP readings jump around, you’ve got a wiring/connector problem.

3. Check live data at hot idle

   Watch these at fully warm idle, in park:

   • MAF g/s – For a 4‑cyl, you usually see roughly 1 g/s per liter of engine at hot idle.
     • If your 4.78 g/s is on a 2.0–2.4L, that’s actually in the ballpark.
   • MAP kPa – At sea level, a healthy engine at idle should be around 25–40 kPa (good vacuum).
     • If MAP is up around 70–100 kPa at idle, P0108 makes sense and the MAP is lying or there’s no vacuum.
   • IAT °C/°F – Should be close to ambient after a cold start, then rise a bit under‑hood.
     • If it shows something crazy like -40°C or 300°F, the IAT circuit is bad (open/short).
   • STFT and LTFT both banks – Note numbers at idle and at 2500 rpm.
     • If trims are high positive at idle and drop closer to 0 at 2500, think vacuum leak.
     • If trims stay high at all RPM, think MAF/MAP/sensor logic.

4. Quick vacuum / intake leak check

   • Listen for hissing around intake boot, PCV hoses, brake booster hose, intake manifold.
   • Spray brake cleaner or carb spray around suspect joints while watching STFT:
     • If trims drop or RPM jumps when you spray a spot, you found a vacuum leak.
   • If no change anywhere and trims are still +12–20%, lean is more likely sensor data than a big leak.

5. Isolate MAF vs MAP

   • With engine idling, watch MAF g/s and MAP kPa while you do a quick snap throttle (blip to ~2500–3000 and let off).
   • Both should respond quickly:
     • MAF should spike up then drop.
     • MAP should jump toward atmospheric (90–100 kPa) on the snap, then drop back down when it returns to idle.
   • If MAF barely moves or is stuck, but MAP behaves, suspect MAF sensor.
   • If MAP is stuck high (P0108) but MAF looks normal, suspect MAP sensor or its wiring.
   • If both look goofy, go back to power/ground checks on the shared sensor circuits.

6. Check O2 sensor behavior (for P0142)

   • Look at Bank 1 Sensor 1 O2 at hot idle.
   • It should switch roughly 0.1–0.9 V (or 0–1 on wideband equivalence) several times per second.
   • If it’s stuck lean and trims are high positive, the O2 might be telling the truth (actual lean).
   • If it’s stuck rich or flat and doesn’t respond even when you create a vacuum leak or add propane, then the O2 sensor or its circuit is suspect.

7. Power/ground check if sensors look dead

   • If MAF/IAT or MAP readings are totally unrealistic:
     • Backprobe with a meter: verify 5V reference, good ground, and signal changes with key on/engine running.
   • No 5V at multiple sensors = possible ECM 5V reference issue or shorted sensor pulling the line down.
   • Only one sensor affected = likely that sensor or its wiring.

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Possible parts (if needed)

• Mass air flow sensor (with integrated IAT) – If P0102/P0113 return, MAF g/s is wrong for RPM, and wiring checks out.
• MAP sensor – If P0108 persists and MAP kPa is high/implausible at idle with good vacuum and wiring.
• Upstream O2 sensor, bank 1 – Only after air‑metering issues are fixed and P0142 remains with a lazy or stuck O2 signal.
• Vacuum/PCV hoses or intake boot – If spray test shows a leak and trims drop when you hit a certain area.

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A few questions

1. What engine size is in this 2014 Mitsubishi, and is the intake system stock?
2. What are STFT and LTFT at hot idle and at about 2500 rpm in park for both banks?
3. What do your MAP kPa and IAT temperature show at hot idle when those codes are present?

Give me those numbers and I can tell you if you’re buying a MAF, a MAP, or chasing a vacuum leak.

Your numbers are pointing at a bad/lying MAF as the main problem, but your MAP data doesn’t make sense as written, so I’m going to treat it like this:

• At idle: MAF ~2.5 g/s
• At 2500 rpm: MAF ~10.5 g/s

On a 2014 Mitsubishi, that’s too low unless this is a tiny engine and you’re barely cracking the throttle. That, plus your P0102/P0113, lines up with a bad MAF/IAT or its wiring.

I need to clear up one thing before I call it 100%:

1. Are those MAP numbers in volts or kPa?
   • You wrote “Map 4.95” and “Map 3.75” – that looks like voltage, not kPa.
   • If MAP is really at 4.95 V at idle, that’s basically P0108 territory (sensor pegged high).

So working hypothesis:

• #1: MAF/IAT sensor is bad or its connector/wiring is compromised.
• #2: MAP sensor or its 5V reference is also screwed up, possibly sharing a bad 5V or ground.

If the 5V line is messed up, both MAF and MAP will lie. That would explain all your air‑metering codes and the lean code.

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Do this in order:

1. Confirm units and conditions

• Tell me:
  • Engine size (2.0 / 2.4 / etc.).
  • Are those MAP values volts or kPa?
  • Are those readings at hot idle in park and 2500 rpm in park?

Without that, we’re guessing on how bad the numbers really are.

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2. Check 5V reference and ground at MAP and MAF

You need a multimeter for this.

• Key ON, engine OFF:

  • Backprobe MAP connector:
    • One pin should be ~5.0 V (reference).
    • One should be good ground (close to 0 V to battery negative).
    • One is signal (usually ~0.5–1.5 V KOEO).
  • Do the same at the MAF/IAT connector (IAT will have 5V ref and signal too).

• If 5V is missing or way off at both sensors:

  • You’ve got a 5V reference problem (shorted sensor or wiring, or ECU issue).

• If 5V and ground are good, but the signal is pegged high (4–5 V) at idle on MAP, the MAP sensor itself is bad.

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3. Re-check MAF behavior after cleaning

You already cleaned it, good. Now:

• Hot idle in park:
  • Note RPM and MAF g/s.
• Hold 2500 rpm in park:
  • Note MAF g/s.

Rule of thumb

Those numbers are bad.

Assuming MAP is in volts:

• Idle: MAP 4.95 V, MAF 2.5 g/s
• 2500 rpm: MAP 3.75 V, MAF 10.5 g/s

That says:

• MAP is basically pegged high at idle → matches P0108 → ECM thinks almost no vacuum.
• MAF is low for 2500 rpm → matches P0102 and your lean code.

Most likely:

1. Bad MAP sensor (or its signal wire shorted to 5V).
2. Weak MAF on top of that.

What I’d do:

1. Check MAP with a meter

   • Key on, backprobe: verify 5V ref, good ground.
   • If ref/ground are good and signal is still ~4.5–5 V at idle → replace MAP sensor.

2. Recheck MAF after MAP fix

   • Warm idle: MAF should be roughly 1 g/s per liter of engine.
   • At 2500 rpm in park, you should see well over 10 g/s on most Mitsu engines.
   • If it’s still low and P0102/P0113 come back → replace MAF.

If you don’t have a meter, you’re basically down to: MAP first (because 4.95 V is clearly wrong), then see what trims and MAF do after.

MAP is basically pegged:

• Idle: MAP 4.95 V, MAF 2.5 g/s
• 2500 rpm: MAP 3.75 V, MAF 10.5 g/s

That MAP signal is wrong and will wreck fueling.

Most likely:

1. Bad MAP sensor (or MAP signal wire shorted to 5V).
2. After fixing MAP, if MAF is still low and P0102/P0113 return, MAF is weak too.

Next move:

• Backprobe MAP: if 5V ref and ground are good and signal stays that high at idle → replace MAP, clear codes, recheck trims/MAF.

MAP is the big problem.

Idle: MAP 4.95 V, MAF 2.5 g/s
2500 rpm: MAP 3.75 V, MAF 10.5 g/s

MAP should be ~1–1.5 V at idle, not 4.95. That will trash fueling and set P0108.

Next steps, shortest path:

• Backprobe MAP: if 5 V ref and ground are good and signal is still that high at idle → replace MAP sensor.
• Clear codes, drive, recheck trims and MAF.
• If P0102/P0113 and low MAF remain, then replace MAF.