Fuel Delivery
P0112
Intake Air Temperature Sensor Low Input
P0112 applies to Intake Air Temperature Sensing and indicates IAT circuit low input, typically interpreted by the PCM as an implausibly hot air temperature on common thermistor designs.\n\nThe PCM monitors IAT circuit signal remaining near the low end of its expected electrical…
Diagnostic Snapshot
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P0112 identifies IAT circuit low input, typically interpreted by the PCM as an implausibly hot air temperature on common thermistor designs involving intake air temperature (IAT) sensor signal circuit. The PCM evaluates IAT circuit signal remaining near the low end of its expected electrical range.
Diagnose the wording of the fault, not the component name alone. Compare scan temperature to actual ambient and unplug/test the sensor circuit according to service information. Use OEM specifications for circuit values and monitor thresholds.
Risk: Low to Moderate. Engine/catalyst risk: Low. Verify the repair by reproducing the original conditions and confirming the monitor completes without a pending or current code.
What You'll Learn
- Exact meaning of P0112
- Best freeze-frame and live-data clues
- Circuit versus mechanical test direction
- Repair verification
Think Like a Technician
Treat P0112 as evidence, not a parts order. Decide whether IAT circuit signal remaining near the low end of its expected electrical range is electrically wrong or accurately reporting a mechanical condition, then prove that path with an independent test.
What This Code Means
P0112 means the PCM judged IAT circuit signal remaining near the low end of its expected electrical range to be outside the calibrated expectation.
The exact fault is IAT circuit low input, typically interpreted by the PCM as an implausibly hot air temperature on common thermistor designs; it does not automatically prove intake air temperature (IAT) sensor signal circuit has failed.
System Overview
Intake Air Temperature Sensing provides the PCM with an input or controlled response used for engine operation and emissions.\n\nDiagnosis should follow the chain of command/input, circuit integrity, physical response and feedback so an electrical defect is not confused with a real mechanical condition.
Why This Code Sets
The monitor runs only when calibration-specific prerequisites such as usable related signals, suitable operating conditions and stable voltage are met.
When enabled, the PCM evaluates IAT circuit signal remaining near the low end of its expected electrical range. If the result remains outside its calibrated window long enough, P0112 is stored. Use exact OEM thresholds rather than universal values.
Common Symptoms
- Check Engine Light
- Possible failed emissions inspection
- Driveability symptoms depend on how strongly the fault changes load, timing, temperature or throttle control
- Possible reduced power, roughness, hesitation, hard starting or fuel-economy change depending on the system
- Fail-safe strategy may substitute a default value or disable an actuator
Most Likely Causes
- 1. Connector or harness fault at the temperature sensor, including open/short, corrosion, poor terminal tension, or contamination
- 2. Biased or failed thermistor/sensor or integrated sensor assembly
- 3. Shared sensor ground/reference problem affecting more than one PID
- 4. For ECT: low coolant, trapped air, thermostat or cooling-system condition that makes the temperature pattern physically wrong
- 5. For IAT: heat soak, sensor placement, intake service error, or airflow condition that explains an unusual but real reading
- 6. PCM input/circuit fault only after sensor and wiring tests prove the external circuit
Freeze Frame Clues
- RPM/load and vehicle speed at failure
- System voltage
- ECT/IAT and time since start
- Relevant Intake Air Temperature Sensing command/feedback PIDs
- Throttle/load or fuel-trim context when applicable
- Companion codes that may share a root cause
Live Data Expectations
Graph the affected temperature PID from cold soak through warm-up. It should begin near a physically plausible ambient value and change smoothly. A value pinned extremely hot/cold, a sudden step, or a temperature curve that cannot match actual engine/air conditions points toward circuit or sensor trouble. For ECT range/performance faults, compare actual metal/coolant temperature and thermostat behavior; for IAT, account for normal heat soak.
Typical Verification Tests
- Confirm P0112 is absent from current and pending memory
- Recreate the freeze-frame operating range
- Graph key Intake Air Temperature Sensing data for smooth/plausible response
- Repeat wiggle/heat test if originally intermittent
- Complete required relearn
- Run the applicable readiness monitor
Before You Condemn
- Confirm exact code definition/component identity
- Save freeze-frame
- Verify voltage and grounds
- Inspect connector/terminal fit
- Compare scan data with physical reality
- Perform OEM circuit/functional test
- Rule out mechanical causes
- Document the failed test before replacement
Before Replacing Parts
Save freeze-frame, verify the exact component/pinout, inspect wiring and perform the simplest physical checks first. Compare scan temperature to actual ambient and unplug/test the sensor circuit according to service information. Replace a part only after its signal, circuit, response or OEM test proves it defective.
Diagnostic Workflow
- Confirm P0112 with a capable scan tool and record whether it is current, pending, history, or intermittent. Do not clear it yet.
- Save freeze-frame data and all companion codes. Note engine speed, load, coolant temperature, intake temperature, throttle position, system voltage, and the PIDs directly related to Intake Air Temperature Sensing.
- Check technical service information for the exact year, engine, calibration, connector pinout, monitor prerequisites, and any known software or harness issues. Do not substitute a generic pinout.
- Perform a focused visual inspection of intake air temperature (IAT) sensor signal circuit, its connector, nearby harness routing, grounds, and any hoses or passages that affect the measurement or actuator.
- Verify battery and charging-system voltage are stable. Low system voltage can distort actuator operation and sensor diagnostics and can create misleading secondary codes.
- Compare scan temperature to actual ambient and unplug/test the sensor circuit according to service information.
- If working with ECT, verify coolant level only on a cold engine and inspect for leaks or trapped air. If working with IAT, verify the sensor is correctly installed in the airflow path and has not been left unplugged after air-filter service.
- After an overnight or adequate cold soak, compare the affected temperature PID with ambient temperature and with another temperature sensor such as ECT or IAT. Large unexplained disagreement is a strong clue.
- Warm the engine or airflow system while graphing the PID. A thermistor-based temperature signal should change smoothly; sudden steps, dropouts, or a value pinned at an extreme suggest circuit trouble.
- Inspect connector terminals for coolant/oil intrusion, corrosion, poor tension, backed-out pins, or harness damage near hot engine components.
- Test sensor reference/bias, ground and signal using the exact OEM diagram. Temperature-sensor circuits are often biased by the PCM, so indiscriminate jumper testing can damage a module.
- If service information provides a temperature/resistance or voltage chart, compare the sensor at known temperatures. Use those specifications instead of a universal resistance number.
- For range/performance ECT faults, independently verify actual coolant temperature and thermostat operation; for IAT performance faults, account for normal heat soak and charge-air heating.
- Repair the proven sensor, connector, wiring or cooling-system cause, refill/bleed coolant correctly when opened, and clear the DTC.
- Repeat a cold-start/warm-up cycle and confirm P0112 does not reset while the temperature curve remains physically believable.
Labor & Inspection Checklist
- Verify VIN/engine and service information
- Scan all related codes and save freeze-frame
- Inspect intake air temperature (IAT) sensor signal circuit connector/harness
- Check relevant fluid/intake/cooling/mechanical basics
- Test power/ground/reference/signal or actuator circuit
- Compare live data with an independent physical check
- Repair/relearn
- Verify monitor completion
Common Repairs
- Repair proven wiring/connector/power/ground fault
- Replace intake air temperature (IAT) sensor signal circuit only after testing proves internal failure
- Correct verified mechanical/fluid/intake/cooling/timing cause
- Perform required relearn and monitor verification
Common Parts
- IAT sensor or MAF/IAT assembly
- Connector pigtail
- Harness repair materials
Shop Notes
Document the PID/circuit result that proves the cause of P0112.
If the fault is intermittent, save a graph during a wiggle/road test. After repair, check pending codes and monitor completion.
Technician Notes
For P0112, focus on IAT circuit signal remaining near the low end of its expected electrical range.\n\nUse loaded circuit testing where appropriate and compare scan data with physical reality. Preserve pre-repair data for verification.
Mechanic's Tip
For P0112, put the most diagnostic PIDs on one graph instead of reading them one at a time. A synchronized graph makes it easier to see whether the PCM command changes first, whether the physical system follows, and whether the feedback signal is late, biased, noisy or simply reporting a real mechanical problem.
Common Mistakes
- Replacing intake air temperature (IAT) sensor signal circuit from the code name alone
- Clearing freeze-frame before diagnosis
- Using universal specs instead of OEM data
- Skipping loaded circuit or physical verification
- Ignoring companion codes
- Failing to verify a pending-code-free drive cycle
Tools Used During Diagnosis
- Enhanced/graphing scan tool
- Digital multimeter
- OEM wiring diagram and service information
- Backprobe leads/terminal test tools
- Battery/charging-system tester
- Infrared/contact thermometer used with awareness of surface-vs-coolant differences
- Cooling-system pressure tester for ECT-related faults
- Resistance/temperature reference from OEM data
Manufacturer Notes
This is a generic OBD-II code. Temperature sensors are commonly negative-temperature-coefficient thermistors, but circuit bias voltage, pull-up strategy, sensor integration, and fail-safe temperature differ by manufacturer. Diagnose from the vehicle's wiring diagram and temperature/resistance chart rather than a universal resistance value.
Customer Explanation
Your vehicle stored P0112, which means the computer found IAT circuit low input, typically interpreted by the PCM as an implausibly hot air temperature on common thermistor designs in the Intake Air Temperature Sensing system. The code does not automatically mean intake air temperature (IAT) sensor signal circuit must be replaced. Wiring, connectors, operating conditions and mechanical problems can create the same code. The correct repair starts by saving the fault data, checking the simple causes, and testing the system under the conditions that caused the warning light.
Frequently Asked Questions
What does P0112 mean?
P0112 means the PCM has identified IAT circuit low input, typically interpreted by the PCM as an implausibly hot air temperature on common thermistor designs involving intake air temperature (IAT) sensor signal circuit. It identifies the monitored fault, not automatically a failed part.
Can I drive with P0112?
Usually suitable only for limited driving when the engine runs normally and no severe warning signs are present. Diagnose promptly.
What should I check first for P0112?
Compare scan temperature to actual ambient and unplug/test the sensor circuit according to service information. Save freeze-frame and related codes before clearing anything.
Does P0112 mean the sensor or actuator is bad?
No. Wiring, connectors, power/ground, mechanical conditions, contamination, shared circuits, calibration and the monitored component itself all have to be considered.
Will P0112 fail an emissions inspection?
Usually yes when the malfunction indicator lamp is commanded on, and clearing the code shortly before inspection can leave readiness monitors incomplete.
Can low battery voltage cause or complicate P0112?
Yes. Low cranking or charging voltage can affect sensor references, actuator response and module diagnostics. Verify electrical system health when voltage in freeze-frame is suspicious.
Should I clear P0112 before diagnosing it?
No. Record freeze-frame, pending codes and companion DTCs first. Clearing memory can erase the conditions that make the fault easier to reproduce.
When is professional equipment justified for P0112?
A bidirectional scan tool, oscilloscope, smoke machine, pressure/vacuum test equipment or OEM service information is justified when basic visual and circuit checks do not clearly prove the fault.
Can P0112 be intermittent?
Yes. Connector fretting, heat-related electronics, harness movement and marginal mechanical control can create faults that disappear in the bay. Graphing data during a road test is often more revealing than a static check.
How do I know the repair is finished?
Reproduce the original operating conditions, confirm the affected live data behaves normally, run the applicable monitor and make sure P0112 does not return as current or pending.
Related Atlas Resources
Review the related system chapter and OEM service information before specification-level testing.
Diagnostic Confidence
High after the code is reproduced and circuit/physical response is verified; Medium when the fault is intermittent and cannot be reproduced
Related Codes
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