Intake Air Temperature Sensor 2 Circuit Low (GM)
What does P1533 mean?
The P1533 code means the vehicle's onboard diagnostic system has detected: Intake Air Temperature Sensor 2 Circuit Low (GM). This is a low severity code.
Common Symptoms
- Check Engine Light illuminated
- Slightly rich fuel mixture
- Marginally reduced fuel economy
- No noticeable drivability symptoms
- Scan tool shows abnormally high intake air temperature
Probable Causes (Ranked by Likelihood)
- Shorted intake air temperature sensor 2 Very High
- Short to ground in the sensor wiring High
- Water intrusion in the sensor connector Moderate
- Damaged wiring harness pinched against metal Moderate
- ECM input circuit fault Low
Step-by-Step Diagnostic Procedure
-
Read the IAT2 sensor value on a scan tool. An abnormally high temperature on a cold engine confirms the short.
-
Inspect the IAT2 sensor connector for moisture, corrosion, or bent pins.
-
Measure sensor resistance. A reading near zero ohms indicates an internal short.
-
Check the wiring from the sensor to the ECM for chafing or shorts to ground.
-
Disconnect the sensor and verify the ECM reads maximum resistance (very cold temperature).
Frequently Asked Questions
What is IAT sensor 2?
Some GM vehicles have two intake air temperature sensors. IAT1 measures ambient air entering the engine, while IAT2 measures the air temperature after the intercooler or further in the intake tract.
Why does a short cause a high temperature reading?
The IAT sensor uses a negative temperature coefficient (NTC) thermistor. A short circuit mimics very low resistance, which the ECM interprets as extremely high temperature.
Where is the IAT2 sensor located?
On turbocharged GM engines, IAT2 is typically located in the intake manifold or charge pipe after the intercooler. On naturally aspirated engines, it may be in the intake manifold.