OBD-II CODE · ENGINE MANAGEMENT / AIR INTAKE SENSORS
The P0112 code means the intake air temperature (IAT) sensor circuit reported voltage too low — a grounded short — so the engine control module (ECM) reads the incoming air as extremely hot and leans out the fuel mixture for heat that isn't there.
Safe to drive, with the same caveat as its twin: the engine runs on bad information. Believing the intake air is scorching, the computer leans the mixture and pulls timing — expect lazy acceleration, occasional pinging and, on some cars, surging idle or stalls. Cheap to fix once it's actually tested.
P0112 — “Intake Air Temperature Sensor 1 Circuit Low Input” — is the diagnostic trouble code (DTC) that mirrors P0113, and the two are best understood as one story told in opposite directions. The IAT sensor is a thermistor: resistance falls as air warms, and the powertrain control module reads temperature from the signal level left on the wire. Break the circuit open and the voltage floats high — P0113, a reading of −40°. Short it to ground and the voltage collapses — a reading pegged impossibly hot, often 250°F and beyond, in an intake that’s actually breathing ordinary Florida morning air.
This code inverts the consequences too. Where P0113’s phantom cold makes the computer richen the mixture, phantom heat makes it lean the mixture and soften ignition timing — the engine-management equivalent of dressing for a heat wave that never arrives. The daily result is subtle: lazy throttle response, mileage that drifts, occasionally a faint ping under load, and on some cars a surging idle or a stall at the worst moment.
The verified-repair record behind this page — the same ~hundred-thread dataset we tallied for P0113 — treats the pair as one family, and its lesson carries over intact: the circuit side — wires and plugs — fixes as many cases as the sensing element does. One cleanly documented kill of the part itself (a VW Jetta’s G42, replaced, codes gone for good) sits alongside chafed signal wires, water-contaminated terminals with their own factory bulletin, and the single most diagnostic clue in the whole family: a history that shows both code P0112 and P0113. A thermistor fails one way and stays there; only damaged copper flexes between short and open as the engine rocks. If your code history shows both numbers, you already know where to look.
The P0112 diagnostic: two-minute troubleshooting in reverse
The test sequence mirrors the twin’s. Resistance check first: the thermistor has a published spec for a given temperature; measure it cold and compare. Out of spec — the element is done, and on cars where the IAT lives inside the MAF assembly that means the air flow sensor as a unit, not a $40 part. In spec — the part is innocent, and the short lives downstream, between the pins and the computer.
Then the sensor connector, opened and actually examined: water intrusion, oil migration and pin corrosion can all bridge a signal toward ground with no visible wire damage. The record’s best cautionary tale is a GM bulletin case where the expected water-intrusion fault turned out to be chafed speaker wires sharing the junction — the kind of thing only looking finds.
Then the harness, with a multimeter, not with parts: signal wire to ground should read open with the pigtail off, and the reference voltage at the IAT sensor circuit should sit near 5 volts key-on — a single volt or less means the short is still live. Anything else is the answer. Our technician runs exactly this ladder during electrical diagnostics, and the invoice shows which rung the fault was standing on.
The Florida wrinkle
Phantom-heat codes have a special irony here: the air over the intake manifold in a Delray Beach summer is hot — which is why the diagnosis leans on impossibility, not discomfort. No airbox on earth breathes 300°F, and the computer can cross-check, because several sensors report temperatures: the IAT, its coolant cousin, the MAF sensor’s own data stream. Underhood heat bakes terminal plastics and wire insulation into these shorts; oil mist from tired crankcase ventilation coats sensing elements until they respond like they’re wrapped in a blanket; and the cold-soak comparison — every temperature reading agreeing at dawn — remains the cleanest free test in the book. Rather than drive the vehicle around guessing, book the diagnosis: the truth, as with its twin, is minutes away and usually inexpensive.
WHAT YOU'D NOTICE
- Check engine light (CEL), often with little change in daily driving
- Scan tool shows intake air temperature pegged impossibly hot — 250°F and beyond
- Sluggish acceleration, dull engine performance or light spark knock (fueling mapped for desert air)
- Surging idle or intermittent stalling on some models
- P0112 alternating with P0113 — the signature of damaged wiring, not a sensor
WHAT TRIGGERS IT
Common causes of P0112
IAT sensor shorted internally
The thermistor's resistance collapses, the signal drops to low voltage, and the reading pegs hot. The verified record includes exactly this — a VW's IAT part (G42 in VW-speak) replaced, codes cleared, never to return. A resistance check against the temperature specification settles it in minutes: a faulty sensor reads out of spec at a known temperature; in spec means keep looking at the circuit.
Related service: Engine & Diagnostics →Signal wire chafed to ground
The low-side mirror of P0113's broken wire: instead of an open circuit, the insulation rubs through and the signal touches metal. The reading slams to maximum hot, often intermittently — over bumps, with engine torque, after underhood work. If the code alternates with P0113, that back-and-forth is practically a signed confession from the loom.
Related service: Electrical →Plug contamination — water, oil or green pins
Moisture or oil inside the housing can bridge the signal toward ground without any visible wire damage. There's even a factory bulletin on one GM platform for water intrusion at a single junction causing a parade of codes — and in the verified record a tech following that bulletin found chafed speaker wires sharing it instead. Disconnect it and inspect both halves; it costs nothing.
Related service: Electrical →Element contaminated or heat-soaked into misreading
An IAT element coated in oil mist (a tired crankcase ventilation system or an over-oiled aftermarket air filter does this) responds slowly and reads hot after heat soak. It may not set the code every day — just lean running and lazy throttle response in traffic, exactly the complaint pattern several threads describe before the part finally trips the threshold.
Related service: Engine & Diagnostics →PCM — last on the list, as always
Same verdict as the record gives P0113: the computer shows up constantly in diagnosis — what the PCM detects is proven at its pins — and almost never as the fix. Reach it only after the test logic has run in reverse: good sensor, good wires, and the input still reading grounded at the module. Even then, shops almost never need to replace the ECM.
Related service: Engine & Diagnostics →ON YOUR MARQUE
What P0112 usually means by make
The signature platform in this dataset: the structured repair record runs the same diagnostic across FX35, FX45, G35, G37, QX4, I35 and M35 — a resistance check of the thermistor at known temperatures, then circuit continuity, in that order. On these VQ-era cars the IAT lives in the MAF sensor assembly, so a failed element means the whole meter, and a healthy one points the bill at the loom instead.
The one cleanly verified sensor kill in this record is a VW — the G42 intake air temperature sensor replaced on a Jetta, both codes gone. Same architecture note as P0113: on many VW/Audi engines the IAT shares the MAF housing, and the plugs suffer Florida heat before the sensors do.
A Cooper S in the record paired P0112 with a stalling complaint — these cars pack intake plumbing tightly around heat sources, and both the sensor's wires and its connections age accordingly. Intermittent hot readings plus a stall history earns the loom a flashlight inspection before any parts order.
An older Malibu thread pairs P0113 with GM's P1111 — 'IAT intermittent' — which is the platform telling on itself: GM logs the intermittence separately, which is half the diagnosis done. Water intrusion at shared connectors has its own bulletin on some models; green pins count as a finding.
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COMMON QUESTIONS
P0112 — FAQs
What does the P0112 code mean?
Trouble code P0112 means the intake air temperature circuit low input condition — electrically, a short to ground that drags the sensor voltage down. Since the IAT is a thermistor whose resistance drops as air warms, a grounded signal decodes as impossibly hot air, often 250°F or more. The computer responds by leaning the fuel mixture and pulling timing for heat that doesn't exist — the exact mirror image of P0113, which reads −40° from an open circuit.
Can I drive with a P0112 code?
Yes — it's an input fault, not a mechanical one, and the computer can detect the bad reading and fall back on safe defaults. The cost is drivability and efficiency: with the module misjudging how much fuel the air needs, expect lazy acceleration, weaker combustion, occasional light knock, reduced fuel economy — even a failed emissions test in some cases, since lean running raises NOx. The fix is usually a cheap part or a simple splice, so living with it buys nothing.
Is P0112 the sensor or the wiring?
The honest answer from the record this page is built on: test, don't guess — the split runs close. A two-minute resistance check against the temperature specification decides it: out of spec means the thermistor died; in spec means the short lives upstream, in the loom or its pins. The strongest circuit clue is alternation — a car that flips between the two codes has damaged copper flexing between short and open, and no thermistor does that.
What does the scan tool show with this code?
An air temp reading pegged at the hot extreme — commonly 250°F or higher — that refuses to adjust with conditions, often with the voltage readings underneath it flat near zero. The sanity check is comparing it to the coolant temperature and ambient after a cold soak: every reading on the car should agree within a few degrees before the first start of the day (on V-engines, the 'sensor 1' in the name just means bank 1). One outlier pinned at an extreme is a circuit problem announcing itself.
How much does it cost to fix P0112?
Same friendly economics as its twin: a stand-alone IAT sensor typically runs $40–$150 installed, cheap at any auto parts counter; when it's built into the mass airflow sensor — common on Nissan, Infiniti, VW and Audi — the part moves to $150–$400; a wiring or connector repair lands around $90–$250, diagnosis and repair often inside one visit with a quick test drive to confirm. The one expensive version of this malfunction is buying the MAF when a chafed wire was the whole story.
Is P0112 the same as P0012?
No — easy to confuse, completely different systems. The P0112 error code is electrical: the intake air temperature circuit reads shorted low. P0012 is mechanical — camshaft timing over-retarded — a different diagnosis entirely. If your scanner shows both, treat them as separate error codes and start with the cheaper electrical fix.