OBD-II Diagnostic Trouble Code
P0112 — Intake Air Temperature Sensor 1 Circuit Low
P0112 means the IAT 1 signal voltage is too low. IAT sensors are thermistors whose voltage drops as temperature rises, so a low voltage reads as a very high air temperature. This usually means a signal wire shorted to ground or a shorted sensor.
Severity 2/5
Truck-relevant
Service soon
Severity
Service soon
Intake Air Temperature Sensor 1 Circuit Low
Code
P0112
Category
Powertrain
Subsystem
Air Flow
Truck-relevant
Yes
What this means for truckers
Service this week on a Cummins X15, Detroit DD15, PACCAR MX-13. Not an immediate stop, but ignoring it usually leads to a more expensive fix downstream.
Before you replace parts — try this first
P0112 on the Air Flow system is most often iat signal wire shorted to ground — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check engine light. The ECM may read very hot intake air, which can cause reduced timing or power, fans running all the time on some trucks, hard cold starts, or extra white smoke on diesels.
Common causes
- CommonIAT signal wire shorted to ground ($80–$350)
- CommonInternally shorted IAT sensor ($60–$450)
- OccasionalWater or corrosion bridging the connector pins ($30–$200)
- RareECM input fault ($900–$2500)
How to fix
Unplug the sensor; if the reading drops to a very cold value, the sensor is shorted
When to use: First step to separate sensor from wiring
Check the signal wire for a short to ground with the ECM and sensor unplugged
When to use: When the reading stays hot with the sensor unplugged
Clean and dry the connector
When to use: When there is moisture or corrosion
Replace the IAT sensor
When to use: When sensor resistance is far below spec
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0100 — Mass or Volume Air Flow Circuit
- → P0101 — Mass or Volume Air Flow Circuit Range/Performance
- → P0102 — Mass or Volume Air Flow Circuit Low Input
- → P0103 — Mass or Volume Air Flow Circuit High Input
- → P0104 — Mass or Volume Air Flow Circuit Intermittent
Frequently Asked Questions
Can I drive with code P0112?
P0112 is severity 2 — service this week. Not an immediate stop, but ignoring it usually compounds the problem. Most common cause for this code is a worn sensor or minor performance fault that won't strand you today but will get more expensive the longer you wait.
How much does it cost to fix P0112 on a commercial truck?
Total repair cost ranges $30–$2500 depending on the root cause. The cheapest fix is usually the first one listed below — IAT signal wire shorted to ground — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0112 fail a DOT inspection?
P0112 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0112 and related codes?
P0112 is closely related to: P0100 (Mass or Volume Air Flow Circuit), P0101 (Mass or Volume Air Flow Circuit Range/Performance), P0102 (Mass or Volume Air Flow Circuit Low Input), P0103 (Mass or Volume Air Flow Circuit High Input). These codes share the same subsystem (air-flow) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0112 is set without the companions, the issue is more isolated.
How do I prevent P0112 from coming back after a repair?
For P0112 (Intake Air Temperature Sensor 1 Circuit Low), prevention centers on the air flow system. Service air filter on time. Clean MAF sensor at every air filter change. Inspect intake boots/hoses for cracks — vibration kills them eventually.