What Does P1117 Mean?
P1117 indicates the Intake Air Temperature (IAT) sensor circuit is intermittently producing a lower-than-expected voltage. This makes the ECM periodically perceive extremely hot intake air, which causes it to lean out the fuel mixture and potentially advance timing incorrectly. The intermittent low voltage suggests a signal wire shorting to ground or a sensor with degraded insulation.
Common Causes
30%
Intermittent short to ground in the IAT sensor signal wire
25%
IAT sensor with intermittent internal short producing low resistance
20%
Moisture or contamination in the IAT sensor connector causing leakage
15%
IAT signal wire chafed against a grounded component
10%
IAT sensor physically damaged or cracked allowing contamination
Diagnostic Steps
1
Step 1: Monitor IAT sensor live data. If it intermittently spikes to 280°F+ when actual conditions are moderate, the circuit is shorting to ground, pulling the voltage low.
2
Step 2: Inspect the IAT sensor connector for moisture, oil contamination, or debris. Even a thin film of conductive contamination can cause a low-resistance path to ground.
3
Step 3: With the sensor disconnected, check for continuity between the signal wire and chassis ground. Any continuity indicates a short to ground in the harness.
4
Step 4: Trace the IAT sensor wiring from the connector to the ECM, looking for chafed insulation or areas where the harness contacts metal components.
5
Step 5: Replace the IAT sensor if internal resistance is below specification or erratic. Clean the connector thoroughly and apply dielectric grease to prevent future moisture intrusion.
Estimated Repair Cost
$25 - $200
Parts + labor, varies by vehicle and location
P1117 indicates the Intake Air Temperature (IAT) sensor circuit is intermittently producing a lower-than-expected voltage. This makes the ECM periodically perceive extremely hot intake air, which causes it to lean out the fuel mixture and potentially advance timing incorrectly. The intermittent low ...
The most common cause of P1117 (Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage) is: Intermittent short to ground in the IAT sensor signal wire
Typical repair costs for P1117 range from $25 to $200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Intermittent lean conditions caused by false high-temperature readings can cause minor hesitation. Extended lean operation may increase exhaust temperatures and stress the catalytic converter, but immediate safety risk is minimal.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1117 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Air Metering
Difficulty
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