Fix P0111: Mechanic’s Solutions That WORKED!

The OBD2 code P0111 indicates a problem with the Intake Air Temperature (IAT) Sensor 1 circuit, specifically relating to its range or performance. This sensor measures the temperature of the air entering the engine, informing the computer to adjust the air-fuel mixture accordingly. Malfunctions can lead to incorrect air temperature readings, affecting engine performance and fuel efficiency.

P0111 quick overview

Meaning	P0111: Intake Air Temperature Sensor 1 Circuit Range/Performance Problem
Is it serious?	Yes, this issue can affect engine performance, fuel efficiency, and emissions.
Possible causes	– Faulty IAT sensor – Damaged or corroded wiring and connectors – Poor electrical connection – Faulty or incorrectly installed Engine Control Module (ECM)
How to diagnose?	Inspect the IAT sensor and wiring for signs of damage or corrosion. Check for correct installation and function of the IAT sensor. Test sensor performance and compare it with manufacturer specifications. Verify ECM operation and update if necessary. Consider other related sensors and circuits for potential faults.

How to fix P0111 – learn from mechanics

I looked into P0111 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 P0111

Vehicle Information 1998 Volvo V70 GLT 2.4L

Issue + Repair History

• Initially displayed code P0111
• Later displayed code P0112, indicating intake air temp of -40 degrees
• Poor fuel economy reported by customer
• MAF sensor replaced, but issue persisted
• Replaced faulty air intake temperature sensor located under the front bumper
• Sensor on the right side of the car feeds information to the ECM, while the sensor on the left side provides temperature reading on the dash

Other OBD2 Codes + Test Results

• Error codes: P0111, P0112

Mechanic Suggestions

• Check manufacturer-specific faults as P0111 might indicate “No faults” in older Volvos
• Verify and reset service light if needed
• Utilize resources like code lookup websites for additional information
• Ensure the integrity and connection of the IAT sensor located in the intake pipe
• Investigate potential issues with the optional outside air temp sensor located on the right side of the HVAC housing

Final Fix

• Replaced faulty air intake temperature sensor located under the front bumper
• Clarified misconception regarding sensor location, as Volvo dealers may misinform about temperature reading source

Case #2: Honda P0111

Vehicle Information 2006 Honda Accord LX 2.4L

Issue + Repair History

• Initially displayed codes: P2610, P0111, & P1116
• Another technician suggested replacing PCM for P2610, followed by coolant temp sensor replacement
• PCM update attempted but already up-to-date
• MAF/IAT sensor and both coolant temp sensors replaced
• Codes P0111 & P1116 persisted after test drives, occasionally accompanied by P2610
• No significant change observed in sensor readings post-replacement

Other OBD2 Codes + Test Results

• Error codes: P2610, P0111, P1116

Mechanic Suggestions

• Investigate if codes return immediately after erasure to determine if there’s an underlying issue
• Inspect engine harness for potential rodent damage
• Ensure engine reaches operating temperature promptly; check thermostat functionality
• Verify engine and PCM grounds for any faults that could disrupt system shutdown procedures
• Pay attention to engine coolant temp sensor #2, located at the bottom of the radiator, susceptible to rust
• Address any connector pin fit issues and consider replacing thermostat with OE part

Final Fix

• Replaced PCM with a used unit
• Immobilizer (anti-theft) module had difficulty programming to used PCM; resolved after proper programming with all customer keys
• PCM replacement addressed the underlying issue causing codes P0111, P1116, and P2610

Case #3: BMW

Vehicle Information 1997 BMW 328i 2.8L

Issue + Repair History

• Engine codes: P0111 (Intake Air Temperature Sensor) and P0443 (Evap. Purge Control Valve)
• Engine replaced by another garage
• Discovered electrical connectors were incorrectly hooked up by previous shop
• Reprogrammed the new engine to the control module to address the issue

Other OBD2 Codes + Test Results

• Error codes: P0111 (Intake Air Temperature Sensor) and P0443 (Evap. Purge Control Valve)

Mechanic Suggestions

• Check the air intake sensor located at the bottom of the intake, towards the back, as it may be unplugged or faulty
• Inspect the Evap. Purge Control Valve, situated at the front bottom of the intake, for any issues or disconnections
• Verify wire harness connections; ensure they are correctly connected and not reversed
• Understand the diagnostic limits and voltage ranges for the Intake Air Temperature Sensor and Evap. Purge Control Valve to diagnose accurately

Final Fix

• Corrected the incorrectly hooked electrical connectors
• Reprogrammed the new engine to the control module to resolve the issues caused by the previous installation

Diagnostic Step	Brief Explanation
Inspect IAT sensor and wiring	Look for damage or corrosion that might impair the sensor’s ability to accurately measure air temperature.
Verify IAT sensor installation and function	Ensure the sensor is correctly installed and functioning as intended by the manufacturer.
Test sensor performance	Use diagnostic tools to test the IAT sensor’s performance and compare it with the expected range.
Check for ECM software updates	Ensure the ECM is up-to-date with the latest software to prevent misinterpretations of sensor data.
Investigate related sensors and circuits	Consider the impact of related components, such as the MAF sensor or coolant temp sensors, on the P0111 code.