OBD-II trouble code
P0112: Intake Air Temperature Sensor 1 Circuit Low
SAE J2012 names a low intake-air-temperature sensor 1 circuit. On 2008 GM GRP09 that is under 45 ohms, a short to ground. On the 1999 Ford PCED it is under 0.2 volt, which that manual also states as 121°C (250°F).
Quick facts
- System
- Powertrain
- Category
- Sensors / Air Intake
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $150
- DIY difficulty
- Beginner DIY
Browse every code in P0100–P0199, or start from the full code library.
What does P0112 mean?
P0112 is Intake Air Temperature Sensor 1 Circuit Low in SAE J2012 APR2002. The 2002 line says circuit low, not circuit low input. Low at the module pin, on a thermistor with a pull-up, is the hot end of the table, because an NTC element has less resistance as it gets hotter and a short to ground has almost none. An open circuit goes the other way and is P0113.
GM's 2008 GRP09 sheet, for the 2.9L LLV, 3.7L LLR, and 4.2L LL8 vehicles in the 2008 grouping matrix, says P0112 detects a continuous short to ground in the intake-air signal or the sensor. The threshold is raw intake-air temperature under 45 ohms. Enables on that row are no vehicle-speed sensor codes, no coolant-temperature sensor codes, engine run time over 10 seconds, coolant temperature under 150°C, and vehicle speed at least 0 km/h. The count is 50 failures out of 63 samples, one sample each 100 ms. Type B. The sheet does not convert 45 ohms into a temperature. Do not borrow the coolant sensor's 47 ohms equals 150°C line and paste it onto this intake-air row.
The 1999 Ford PCED says the intake-air signal is under the self-test minimum, and it states that minimum as 0.2 volt or 121°C (250°F). Causes are a grounded circuit, a damaged sensor, an improper connection, and a damaged PCM. The aide says to disconnect the sensor and simulate 1.0 volt on the signal. If the PID matches, check the sensor. If it does not, check the circuit and the PCM. The same manual's high code is 4.6 volts or −50°C, so the two ends are published as a pair.
The 2004 GM L61 file describes P0112 as a short to voltage or a signal out of range high, with the threshold written as under 48 counts and greater than 128°C. That count scale is not volts and not the GRP09 ohm scale. A count of 48 means nothing on the Ford 0.2-volt test. The L61 enable wants vehicle speed over 15 mph and run time over 320 seconds.
Common causes
- On GRP09, a short to ground in the intake-air signal or inside the sensor, once resistance is under 45 ohms
- On the 1999 Ford PCED, a grounded circuit or a damaged sensor that takes the signal under 0.2 volt, stated as 121°C (250°F)
- An improper connection on that Ford list, found while the sensor is unplugged for the 1.0-volt simulation
- On the 2004 L61 file, the short-to-voltage or out-of-range-high condition that file counts as under 48 counts and over 128°C
- A damaged PCM, which the Ford aide reaches when the simulated 1.0 volt does not appear on the PID
Symptoms
- Malfunction indicator lamp with P0112
- On GRP09, raw intake-air resistance under 45 ohms after more than 10 seconds of run time, with coolant under 150°C
- On the 1999 Ford PCED, a PID under 0.2 volt, displayed as 121°C (250°F) or hotter
- On the L61 file, a count under 48, displayed as over 128°C, after more than 320 seconds and above 15 mph
- The opposite freeze, a very cold reading, belongs to the high and open codes, not to this one
Diagnostic steps
- 1.Read the PID's units before comparing it with a number. GRP09 is ohms, fail under 45. The 1999 Ford PCED is volts, fail under 0.2, also stated as 121°C. The L61 file is counts, fail under 48, also stated as over 128°C. A single hot-temperature story does not survive that split.
- 2.On the Ford test, key off, disconnect the sensor, and simulate 1.0 volt on the signal circuit. A matching PID means the harness can carry a mid-scale voltage, so the under-0.2-volt result was in the sensor or its connector. A PID that stays low means the signal is still grounded or the PCM input is not seeing the simulation.
- 3.On GRP09, measure the sensor's resistance unplugged, and measure the signal wire to ground with both ends disconnected and the ignition off. Under 45 ohms through the sensor, with the wire clear of ground, replaces the sensor. Under 45 ohms from the signal wire to ground, with the sensor unplugged, is the short the strategy line names. Do not jumper a combined mass-airflow connector. The other pins are the airflow circuit.
- 4.Respect the enable. GRP09 wants more than 10 seconds of run time and coolant under 150°C. The L61 file wants more than 320 seconds and speed over 15 mph. A cold-bay measurement that ignores those gates is not the monitor.
- 5.Repair the grounded wire, the connector, or the sensor the test isolated. The Ford list includes a damaged PCM when the simulation does not arrive. GRP09 does not add a PCM replacement sentence on this row.
- 6.Clear the code and confirm the reading is no longer under the same limit. An infrared thermometer on the air box is not the Ford 0.2-volt test or the GRP09 45-ohm test.
Repair cost
$120 – $150
A shorted intake-air temperature sensor is about $120 to $150 installed. That is the part the low-circuit charts replace after the wiring test.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with intake air temperature sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is a beginner-friendly repair. Common hand tools, a free afternoon, and a willingness to follow a procedure are usually enough. The risk of causing a bigger problem is low if you read up on your specific vehicle first.