P0099
Fix within a few daysYour engine computer is getting inconsistent or unreliable temperature readings from Intake Air Temperature (IAT) Sensor 2.
Code P0099 means your engine computer is getting inconsistent readings from Intake Air Temperature Sensor 2. Common causes: Faulty IAT sensor (70%), wiring issues (25%). Drivability: Yes, safe to drive, but fix soon. Repair cost: $30-$100 DIY, $100-$250 professional.
Can I Drive With P0099?
Yes, safe to drive
No restrictions, but fix within a few days to prevent further issues and improve performance.
Stop driving immediately if: Engine is severely overheating, significant power loss, or any loud knocking noises.
Symptoms of P0099
- 1Check Engine Light is on
- 2Reduced engine power or sluggish acceleration
- 3Rough idle or stalling
- 4Poor fuel economy
- 5Engine may run rich or lean
Common Causes of P0099
Parts most likely causing this code, ranked by probability
The IAT sensor itself is faulty, sending intermittent or incorrect temperature data to the engine computer.
70% of P0099 cases are fixed by replacing this part
Damaged, corroded, or loose wiring or a faulty connector prevents a consistent signal from reaching the engine computer.
25% of P0099 cases are fixed by repairing wiring or connector
A rare internal fault within the engine computer can misinterpret or incorrectly process the IAT sensor signal.
5% of P0099 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the IAT Sensor 2 connector and wiring for any obvious damage, corrosion, or loose connections.
- Ensure the air filter is clean and the air intake system has no leaks or obstructions near the sensor.
How to Diagnose P0099
- 1Visually inspect IAT Sensor 2 and its wiring for any obvious damage, corrosion, or loose connections.
- 2Use an OBD-II scanner to monitor live data for IAT Sensor 2. Look for erratic temperature readings that do not match ambient temperature or engine operating conditions.
- 3Disconnect the IAT Sensor 2 connector and test the sensor's resistance with a multimeter. Compare readings to factory specifications.
- 4Check the continuity and resistance of the IAT Sensor 2 wiring harness back to the ECM/PCM using a multimeter.
- 5If all sensor and wiring checks pass, consider further diagnostics for the ECM/PCM, though this is a rare cause.
P0099 on Popular Vehicles
Toyota Camry
2007-2024On many Camry models, IAT Sensor 2 is a standalone sensor located in the intake tube after the air filter box. It's usually easy to access and replace.
75% fixed by replacing IAT Sensor 2
Honda Accord
2003-2024For Accord models, IAT Sensor 2 is often integrated into the MAF sensor. If this is the case, you may need to replace the entire MAF sensor assembly, or clean it thoroughly first.
70% fixed by replacing IAT Sensor 2 (or MAF if integrated)
Ford F-150
2004-2024On Ford F-150 trucks, IAT Sensor 2 can be a separate sensor in the intake manifold or part of the MAF sensor, depending on the engine. Always verify its location before starting diagnosis.
70% fixed by replacing IAT Sensor 2
Frequently Asked Questions
What does P0099 mean?
P0099 indicates that your vehicle's engine computer has detected an intermittent or erratic signal from Intake Air Temperature (IAT) Sensor 2. This means the temperature readings from this sensor are not consistent or reliable.
Can I drive with P0099?
Yes, you can drive safely with P0099, but you should fix it within a few days. The engine computer will use a default value, which can lead to reduced fuel economy and performance. Prolonged driving with incorrect air temperature data can cause the engine to run rich or lean, potentially damaging other components.
Will P0099 clear itself?
No, P0099 will not clear itself. The engine computer stores this code because it detects a persistent issue with the IAT Sensor 2 signal. You must diagnose and fix the underlying problem, then clear the code with an OBD-II scanner.
How do I fix P0099 myself?
Start by visually inspecting the IAT Sensor 2 and its wiring for damage. If the sensor looks good, test its resistance with a multimeter and compare it to specifications. If the sensor is faulty, replace it. If the sensor tests good, check the wiring for continuity and repair any breaks or corrosion.
How much does it cost to fix P0099?
A DIY fix for P0099 typically costs $30-$100 for a new IAT sensor. If you take it to a professional shop, expect to pay $100-$250, which includes parts and labor for diagnosis and replacement.
P0099 keeps coming back - why?
If P0099 keeps returning, it means the root cause was not fully addressed. This often happens if you replaced the sensor but the issue was actually in the wiring or connector. Always perform thorough diagnostic steps to rule out wiring problems before replacing the sensor, and ensure the new sensor is functioning correctly.
Will P0099 fail emissions/smog test?
Yes, P0099 will cause your vehicle to fail an emissions or smog test. A Check Engine Light (CEL) illuminated for any reason, including P0099, is an automatic failure in states with emissions inspections.
What's the difference between P0099 and P0095?
P0095 indicates a general 'Circuit Malfunction' for IAT Sensor 2, meaning the computer sees an open, short, or out-of-range signal. P0099 specifically means the signal is 'Intermittent/Erratic,' indicating the sensor is sending inconsistent or unreliable data, rather than a complete circuit failure.
P0099 on Ford F-150?
P0099 on a Ford F-150 points to the same IAT Sensor 2 issue as on any other vehicle. On many F-150s, IAT Sensor 2 is integrated into the Mass Air Flow (MAF) sensor, or it can be a separate sensor located in the intake ducting. Diagnosis follows the same steps: check the sensor, then the wiring.
Questions to Ask Your Mechanic
Did you check the live data for IAT Sensor 2 to see if the readings are erratic or stuck?
Good answer: Yes, I monitored the IAT 2 readings on the scanner. They were jumping around wildly, or showing an inconsistent temperature compared to IAT Sensor 1 or ambient air.
What did you find when you inspected the wiring and connector for IAT Sensor 2?
Good answer: I checked the harness for any fraying, corrosion, or loose pins. The wiring showed good continuity, but the connector itself had some corrosion, which I cleaned.
Repair Cost Estimate
DIY Repair
Parts only
$30-$100
Shop Repair
Parts + labor
$100-$250
Save $70-$150 by doing it yourself
Difficulty
beginner
Time
0.5-1 hours
Beginner-friendly - The IAT sensor is typically easy to locate and replace with basic hand tools and a multimeter for testing.
Cost of Waiting
Ignoring P0099 means your engine is operating with incorrect air temperature data. This leads to poor fuel economy, reduced power, and can cause the engine to run too rich or too lean. Running rich can damage your catalytic converter ($800-$2,500 repair), while running lean can cause engine overheating or internal damage.
While You're In There...
A dirty air filter can restrict airflow and affect sensor readings. It's a low-cost maintenance item often accessed when working on intake sensors.
If IAT Sensor 2 is integrated into the MAF sensor, cleaning the MAF sensor can resolve intermittent issues. Even if separate, a clean MAF ensures accurate airflow data.
Tools You'll Need
- OBD-II scanner
- Multimeter
- Socket set or wrench set
- Screwdriver set
- Wire brush (for cleaning connectors)
P0099 is a common sensor code. Most repairs are straightforward, involving a simple sensor replacement or wiring repair, and your engine will run much better afterward.
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Your Next Steps
Step 1: Visually inspect the IAT Sensor 2 wiring harness and connector for any damage, corrosion, or loose pins. Repair any issues found.
Step 2: Use an OBD-II scanner to monitor live data for IAT Sensor 2. If readings are erratic or stuck, disconnect the sensor and test its resistance with a multimeter. Compare to factory specifications.
Step 3: If the sensor tests faulty, replace the IAT Sensor 2. If the sensor tests good, check the wiring for continuity back to the ECM/PCM. If wiring is good, further diagnosis of the ECM/PCM may be needed, but this is rare.