Air Temperature Internal Sensor Circuit Short To Battery
The air temperature sensor is sending a signal that's too high, as if it's shorted directly to the vehicle's battery voltage. Think of it like a wire touching the positive battery terminal instead of properly measuring the actual air temperature.
The ECM monitors the intake air temperature (IAT) sensor's voltage signal to adjust fuel mixture and ignition timing. The sensor should produce a voltage between 0.2V-4.8V corresponding to air temperature. When shorted to battery, the voltage stays at or near 5V continuously, indicating an impossible temperature reading.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| IAT Sensor Voltage | 0.2V to 4.8V (varies with temperature) | Above 4.8V or constant 5V (shorted to battery) |
| Implied Air Temperature | -40°C to 125°C | Below -40°C (sensor reading malfunction) |
Code B1252 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B1252 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.