OBD2 Diagnostic Code
P0112
Intake Air Temperature Sensor Circuit Low Input — Causes & How to Fix It Yourself
P0112 looks alarming on your scanner, but this is one of the easiest sensor codes to diagnose at home. In most cases it comes down to a corroded connector or a failed sensor — not a major engine problem. Here's exactly what to check before spending a dime at a shop.
Severity
4 / 10
Low-Moderate. Engine damage is unlikely, but performance and fuel economy are affected.
Safe to Drive?
Generally Yes
Short-term driving is okay. The ECM uses a fallback value. Fix it within a week or two.
Typical DIY Fix Cost
Very Low
Connector cleaning is free. A replacement IAT sensor typically costs very little at any parts store.
🔍 What This Code Means
Your engine has a small sensor in the intake air stream called the Intake Air Temperature (IAT) sensor. Its job is simple: measure how hot or cold the air is before it enters the engine. The ECM uses that reading to fine-tune fuel delivery and ignition timing — warmer air is less dense, so less fuel is needed; colder air is denser, so more fuel is needed.
The IAT sensor works like a thermistor — a resistor that changes its electrical resistance based on temperature. At cold temperatures (say 32°F / 0°C) resistance is high and the signal voltage on the circuit is high, around 3.5–4.5V. As air temperature rises, resistance drops and voltage drops — typically sitting around 1.5–2.5V at normal operating temperature.
💡 P0112 is set when the ECM detects that the IAT sensor signal voltage has dropped below roughly 0.1–0.2 volts — far outside the normal range. This is what the code calls a "Low Input." The ECM interprets this as an implausibly hot air temperature reading, or more likely, a short circuit in the sensor wiring.
When P0112 is active, the ECM cannot trust the real air temperature. On most vehicles it substitutes a fixed fallback value — usually a warm default around 68–86°F (20–30°C) — to keep the engine running. That is why the car often drives reasonably well despite the fault. But the ECM is flying blind, and fuel trim and ignition timing are no longer fully optimized for the actual conditions.
⚡ Common Symptoms
P0112 is often subtle. Some drivers notice nothing unusual beyond the check engine light. Others notice a combination of the following, especially on cold starts.
Check engine light (only sign in many cases)
The ECM detects the out-of-range voltage and illuminates the MIL. Many drivers have no other symptoms at all.
Poor cold-start performance
The ECM can't read the actual cold air temperature, so the cold-start enrichment fuel strategy is off. Hard starts on cold mornings are common.
Reduced fuel economy
Without accurate air temperature data, the fuel mix is slightly off. Expect a small but noticeable drop in MPG over time.
Rough idle after cold start
The engine may idle unevenly for the first few minutes of a cold start while the ECM tries to compensate with the fallback value.
Failed emissions test
An active check engine light means an automatic fail in most states and countries regardless of actual emissions levels.
Slight hesitation on acceleration
Occasional stumbling from a stop, particularly in cold weather when the fallback temperature value diverges most from reality.
🎯 Most Likely Causes
P0112 is almost always an electrical fault — not a mechanical engine problem. Work through this list from top to bottom. Most cases are resolved before reaching cause #3.
1
Corroded or damaged IAT sensor connector
The connector pins at the IAT sensor are exposed to the intake air path — moisture, oil mist, and heat cycles cause corrosion over time. A corroded pin drops the circuit resistance dramatically, pulling signal voltage down. This is the cause in roughly 4 out of 10 P0112 cases and costs nothing to check or clean.
~ 38% of cases
2
Failed IAT sensor (internally shorted)
The thermistor element inside the sensor can fail in a short-circuit mode — its internal resistance collapses to near zero, pulling signal voltage down below the ECM's minimum threshold. At this point the sensor cannot be cleaned back to life. A replacement sensor costs very little and usually solves P0112 immediately.
~ 30% of cases
3
Short to ground in the signal wire
If the signal wire insulation has chafed through against a sharp metal edge — common near air filter housings and throttle body boots — it can contact the chassis and ground the circuit. This drives voltage to near zero just like a failed sensor, but the sensor itself is fine. Inspect the harness routing carefully with the circuit live.
~ 18% of cases
4
IAT sensor integrated into MAF sensor (wiring fault)
On many modern vehicles, the IAT sensor is built into the MAF sensor housing as a combined unit. A fault in the MAF sensor wiring harness can affect the IAT signal simultaneously. If P0101 or P0100 appears alongside P0112, suspect the MAF sensor harness before replacing anything individually.
~ 10% of cases
5
Faulty ECM or PCM (rare)
In very rare cases a failed input circuit inside the ECM itself causes a false P0112. Only suspect this after a confirmed good sensor, clean connector, and verified wiring with no shorts. A new sensor that still reads below 0.2V with no wiring faults is a strong indicator of an ECM problem.
~ 4% of cases
🔧 What to Check First
These three checks cover about 85% of all P0112 cases. No special tools are needed for the first two. An inexpensive multimeter handles the third. Start here before buying any parts.
1
Inspect and clean the IAT sensor connector
Locate the IAT sensor — it's typically in the air intake duct or air filter housing, though on many vehicles it's integrated into the MAF sensor body. Unplug the connector and look at the pins. Green or white powdery buildup is corrosion. Spray the connector with electrical contact cleaner, work the connector on and off a few times to break up oxidation, and let it dry completely before reconnecting. Reconnect firmly, clear the code, and drive a full warm-up cycle. This single step resolves the problem in a significant number of cases.
2
Inspect the wiring harness for chafing or pinching
Trace the wiring harness from the IAT sensor back toward the firewall. Look for spots where the wire bundle contacts a sharp bracket edge, a hot exhaust component, or a moving part like the throttle cable. Chafed insulation can create an intermittent short that only shows up when the wire flexes in a certain position. Wiggle the harness with the engine running — if the live data reading changes, you have found a wiring fault. Wrap any bare spot with self-fusing silicone tape and reroute if needed.
3
Measure the IAT sensor resistance with a multimeter
Unplug the sensor and measure resistance across the two sensor pins directly — do not measure at the connector harness side for this test. At room temperature (68°F / 20°C) a healthy IAT sensor reads approximately 2,000–3,000 ohms (2–3 kΩ). A reading near zero ohms confirms the sensor is internally shorted and needs replacement. A reading of infinite resistance (OL) points to an open circuit. Either extreme will set P0112 or its companion code P0113.
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⚠️ Common Misdiagnosis
P0112 is one of the most over-diagnosed codes when it comes to unnecessary parts replacement. These three mistakes are extremely common — and each one is avoidable with an inexpensive multimeter and 15 minutes of your time.
⚠ Misdiagnosis #1 — Replacing the MAF sensor instead of testing the IAT sensor first
On vehicles where the IAT sensor is integrated into the MAF sensor housing, some shops immediately quote a full MAF sensor replacement when P0112 appears. The IAT element failing inside the MAF unit does not necessarily mean the MAF flow-measurement component has failed. Always test the IAT sensor resistance separately from the MAF signal before condemning the entire MAF assembly — replacement MAF sensors cost many times more than a standalone IAT sensor.
Potential savings: MAF sensor replacement vs. standalone IAT sensor cost
⚠ Misdiagnosis #2 — Replacing the sensor before inspecting the connector
A corroded IAT connector produces an identical P0112 to a failed sensor — the voltages look the same on a scanner. The correct first step is always to clean the connector with electrical contact cleaner, clear the code, and retest. Skipping this step and going straight to sensor replacement means throwing parts at a problem that costs nothing to fix. Ask any shop quoting a sensor whether they have cleaned the connector first.
Potential savings: Sensor part cost and labor
⚠ Misdiagnosis #3 — Condemning the ECM without ruling out wiring faults
When a new sensor still triggers P0112 after installation, the next step is always thorough wiring inspection — not ECM replacement. A wire shorted to ground anywhere in the circuit will drag the signal voltage down regardless of how many times you replace the sensor. ECM replacement is a last resort after confirmed good sensor, confirmed clean connector, and a wiring harness that has been fully inspected and cleared of shorts.
Potential savings: ECM replacement is one of the most expensive repairs on any vehicle
💰 Estimated Repair Cost
DIY cost = parts only. Shop cost = parts plus labor. Ranges vary by vehicle make, region, and shop rate. Use these as a planning guide — not a fixed quote.
Connector cleaning (electrical contact cleaner)
DIYFree – Minimal
ShopLow
LevelVery Easy
Standalone IAT sensor replacement
DIYVery Low
ShopLow–Moderate
LevelVery Easy
Wiring harness repair (short to ground)
DIYMinimal
ShopModerate
LevelEasy–Moderate
MAF/IAT combo sensor replacement
DIYModerate
ShopModerate–High
LevelEasy
ECM/PCM replacement (rare, last resort)
DIYHigh
ShopVery High
LevelProfessional
✅ The vast majority of P0112 cases are resolved with connector cleaning or a very inexpensive sensor replacement. Do the resistance test before buying any parts — it takes 5 minutes and tells you exactly what you need.
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🚗 Most Reported On
P0112 can appear on any gasoline vehicle with an IAT sensor — which is virtually every OBD2-equipped car and truck made after 1996. These models report it most frequently based on owner data and repair records.
Ford F-150 (2004–2014, 4.6L / 5.4L)
Chevrolet Silverado (2003–2013, 5.3L)
Honda Accord (2003–2012, 2.4L / 3.0L)
Toyota Camry (2007–2015, 2.5L / 3.5L)
Dodge Ram 1500 (2004–2012, 4.7L / 5.7L)
Ford Explorer (2002–2010, 4.0L)
Nissan Altima (2005–2013, 2.5L)
Jeep Grand Cherokee (2005–2012, 3.7L / 4.7L)
❓ Frequently Asked Questions
Can I drive with P0112 active?
Yes, in most cases — P0112 rarely causes immediate danger. The ECM switches to a fallback temperature value and keeps the engine running. However, fuel economy and performance are degraded, cold-start emissions are higher, and an active check engine light will fail most emissions inspections. Get it diagnosed within a week or two rather than ignoring it indefinitely.
What voltage should the IAT sensor read?
At room temperature (around 68°F / 20°C) the IAT sensor signal wire should read approximately 2.0 to 2.5 volts. At very cold temperatures the voltage rises toward 4.5V. At hot intake temperatures after a warm engine soak it drops toward 0.5V. P0112 is set when the signal drops below about 0.1 to 0.2 volts — which the ECM interprets as an extreme high-heat reading or, more commonly, a short circuit somewhere in the sensor circuit.
Why does P0112 come back after I clear it?
Clearing the code does not fix the fault. The ECM continuously monitors the IAT sensor signal. As soon as conditions are met — usually within one drive cycle — it detects the out-of-range voltage again and resets the code. Fix the root cause first: inspect the connector for corrosion, measure the sensor resistance with a multimeter, and trace the wiring for shorts before clearing the code and retesting.
Can P0112 cause a rich running condition?
Yes. When the ECM sees a very low IAT signal voltage, it interprets incoming air as extremely hot. To compensate for what it thinks is hot, less-dense air, it may enrich the fuel mixture — adding more fuel than conditions actually require. This leads to reduced fuel economy and higher hydrocarbon emissions. It can also cause a fuel smell from the exhaust under some cold-start conditions.
Is P0112 the same as P0113?
No — they are opposite faults. P0112 means the IAT circuit voltage is too low (below the minimum threshold), typically caused by a short to ground or an internally shorted sensor. P0113 means the voltage is too high (above the maximum threshold), usually caused by an open circuit — a broken wire or disconnected connector. If both codes appear together, the sensor or connector is the most likely culprit, not the wiring harness.
🔗 Related Codes
These codes share the same sensor family, similar root causes, or commonly appear alongside P0112.
This guide is for informational purposes only. Always consult a qualified mechanic before performing any vehicle repair. OBDPlatform is not responsible for actions taken based on this content.