Fix P0112: Mechanic’s Solutions That WORKED!

The OBD2 code P0112 is indicative of a low input problem in the Intake Air Temperature (IAT) Sensor Circuit. This means the sensor is reporting an unrealistically low temperature reading to the vehicle’s computer (ECM), which can distort the air-fuel ratio, impairing engine performance and efficiency. This issue often results from electrical problems like shorts or disconnections in the circuit.

P0112 quick overview

Meaning	P0112: Intake Air Temperature Sensor Circuit Low Input
Is it serious?	Yes, because it can lead to poor engine performance, increased emissions, and potential damage to the engine.
Possible causes	– Faulty or disconnected IAT sensor – Short to ground within the wiring circuit – Corroded or poor electrical connections – Faulty Engine Control Module (ECM)
How to diagnose?	Inspect the IAT sensor and its connections for signs of damage or disconnection. Test the wiring circuit for shorts to ground or open circuits. Verify the sensor’s voltage readings to ensure they align with manufacturer specifications. Check the ECM for faults or necessary updates. Consider the impact of related components, such as the MAF sensor, if integrated with the IAT.

How to fix P0112 – learn from mechanics

I looked into P0112 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Volvo P0112

Vehicle Information 1997 Volvo 850 GLT 2.4L

Issue + Repair History

• CEL on with code P0112 (Intake air temp sensor signal low)
• AllData showed the location of the IAT as being near the bumper, but the sensor found there was for outside air temperature for HVAC
• Found open circuit from outside temp sensor to ECM causing incorrect readings
• Troubleshooting circuit to diagnose the issue

Other OBD2 Codes + Test Results

• Error code: P0112 (Intake air temp sensor signal low)

Mechanic Suggestions

• Check ECM or connector for possible fault causing the error code
• Look for two outside air temp sensors below and behind the front bumper, one on each side
• Search for the IAT sensor located before the MAF (Mass Air Flow) sensor, typically inserted in the rubber hose between the air filter box and the MAF
• Replace the ECT sensor located in the thermostat housing, as Volvo may refer to it as IAT
• Inspect the lower air dam on the LH side for the IAT sensor, as it may have been knocked off or damaged
• Consider that the sensor for the temperature gauge in the dash may not be related to the IAT reading, as there are usually two identical sensors mounted on either side of the air guide
• Look for the ambient temp sensor at the air guide’s front bottom of the bumper
• Verify the exact nature of the error code (P0112) to ensure accurate diagnosis, as it could potentially indicate an ECM issue

Final Fix

• Resolved by replacing the IAT sensor

Case #2: Volkswagen P0112

Vehicle Information 2001 Volkswagen Passat GLS 2.8L

Issue + Repair History

• Complaint of surging under load and CEL on
• Retrieved codes: P0112 (air intake sensor low input), P0300, P0302, P0304 (misfire codes), P1394 (coil power output stage)
• Reset codes and road tested, car surged under load intermittently
• Observed temperature pegging out at 143°F and bouncing back to true intake temp with surge
• Wiggle tested harness for possible short to ground, no reaction
• Replaced air intake sensor wire to the ECU, although wire ohmed out ok

Other OBD2 Codes + Test Results

• Error codes: P0112 (air intake sensor low input), P0300, P0302, P0304 (misfire codes), P1394 (coil power output stage)

Mechanic Suggestions

• Common issue with air mass meters on these cars; since the IAT sensor is in the AMM, consider replacing it
• Check for a restriction at the air cleaner housing inlet, including the screen, which may become clogged
• Verify correct spark plugs (NGK laser platinum) and clean throttle body, as incorrect plugs and throttle body issues can cause surging
• Confirm all ground wires/tabs are corrosion-free, ensure continuity between ground wires & its terminal, and check temp sensor for any issues

Final Fix

• Replacing the air intake sensor wire to the ECU resolved the issue, even though the wire ohmed out ok

Case #3: Dodge P0112

Vehicle Information 1996 Dodge Stratus ES 2.5L

Issue + Repair History

• Complaint of MIL lamp on with two codes: 1496 (5-volt reference low) and P0112 (IAT voltage low)
• No voltage at the air charge sensor, but 5-volt signal coming out of the ECM at all sensors
• Checked for opens in the wires, all checked okay
• Tried to clear codes, but they come right back
• Grounds are clean and tight
• Issues with A/C high-pressure switch and air charge sensor; ECT and IAT values are the same and go negative when ECT is disconnected

Other OBD2 Codes + Test Results

• Error codes: 1496 (5-volt reference low), P0112 (IAT voltage low)

Mechanic Suggestions

• Check for a problem with the IAT, possibly a short to ground; test voltage on the 5V/signal wire with the sensor unplugged (should read 5 volts) and plugged (should read 1-3 volts)
• Inspect wiring harness for oil leaks or seepage, as oil can cause breakdown and wire shorts
• Monitor the 5V reference and unplug individual sensors to identify any device pulling the 5V ref down when the circuit is loaded

Final Fix

• Replacing the ECM resolved the issue; a bad ground at the right strut tower was identified, and as soon as the new ECM was installed, the ground wire started to smoke, indicating the problem was fixed.

Diagnostic Step	Brief Explanation
Inspect IAT sensor and connections	Look for damage, disconnections, or corrosion that might be causing incorrect temperature readings.
Test wiring for shorts or opens	Check the sensor’s wiring circuit for any shorts to ground or open circuits that could cause low input signals.
Verify sensor voltage	Measure the voltage at the IAT sensor to ensure it matches expected values based on temperature.
Check ECM	Examine the Engine Control Module for any signs of fault or the need for software updates.
Assess related components	Evaluate the condition of related sensors and components, such as the MAF sensor, that might influence IAT readings.