Aux Heater Overheat Sensor Circuit Short to Ground
The auxiliary heater's overheat sensor wire is shorted to ground, like a frayed electrical cord touching metal. The ECU can't read the sensor's temperature signal because the short is preventing it from sending proper voltage.
The ECU monitors voltage from the aux heater overheat sensor, expecting a resistance-based signal that increases with temperature. When shorted to ground, the voltage reads near 0V continuously, triggering a fault. The ECU uses this signal to prevent heater overheating and control heating cycles.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 0.5–4.5V (varies with temperature) | Below 0.1V (shorted to ground) |
| Sensor Resistance | 10kΩ–100kΩ (temperature-dependent) | Less than 5Ω (short to ground) |
Code B2458 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, B2458 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.