What Does P0099 Mean?
The ECM has detected an intermittent or erratic signal from the intake air temperature sensor 2 circuit on bank 1. The sensor is providing readings that fluctuate rapidly or cut in and out, rather than showing a smooth, continuous temperature reading. The driver may notice intermittent rough running, hesitation, or momentary power loss as the ECM reacts to the erratic temperature data.
Common Causes
35%
Loose or intermittent connection at the IAT sensor 2 connector
25%
Chafed or partially broken wire in the sensor harness making intermittent contact
20%
Failing IAT sensor 2 with intermittent internal connection
15%
Corroded connector pins creating intermittent high-resistance contact
5%
Electromagnetic interference from nearby ignition components affecting the signal
Diagnostic Steps
1
Monitor the IAT sensor 2 PID in real-time and look for sudden jumps, dropouts to -40F, or spikes to 250F+. Record the pattern to differentiate between an intermittent open (spikes to -40) vs. intermittent short (spikes high).
2
Wiggle-test the IAT sensor 2 connector and harness while monitoring the PID. If the reading changes erratically during the wiggle test, the connection point where it changes is the fault.
3
Inspect the connector pins for corrosion, spread female terminals, or pushed-back pins. Clean with electrical contact cleaner and verify a firm, positive connection.
4
Check the harness for chafing, especially where it passes through brackets, clips, or near sharp edges. A partially broken wire can make and break contact with vibration.
5
If the connector and wiring are in good condition, replace the IAT sensor 2. Intermittent internal failures are common in thermistor-type sensors exposed to heat cycling.
Estimated Repair Cost
$40 - $250
Parts + labor, varies by vehicle and location
The ECM has detected an intermittent or erratic signal from the intake air temperature sensor 2 circuit on bank 1. The sensor is providing readings that fluctuate rapidly or cut in and out, rather than showing a smooth, continuous temperature reading. The driver may notice intermittent rough running...
The most common cause of P0099 (Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 1) is: Loose or intermittent connection at the IAT sensor 2 connector
Typical repair costs for P0099 range from $40 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. Intermittent IAT sensor faults may cause momentary performance glitches but the ECM can compensate with other sensor inputs. On forced-induction vehicles, boost may be momentarily limited. No immediate safety risk but repair should be done soon to prevent chronic driveability issues.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0099 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Sensor System
Difficulty
Type
Generic (SAE)
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