Sensor Reference Voltage B Circuit High
The ECU detected that the reference voltage signal for sensor bank B is too high, similar to a voltage regulator supplying too much power to a sensor. This prevents the sensor from working correctly and can cause the engine to run poorly.
The ECU monitors the reference voltage (typically 5V) supplied to sensors on bank B through a dedicated circuit. When this voltage exceeds the normal threshold, the ECU detects an overvoltage condition and sets the fault code. This prevents accurate sensor readings and throws off fuel trim and ignition timing calculations.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Reference Voltage B | 4.75V to 5.25V | Above 5.5V or shorted high |
| Circuit Load Current | 10-200mA depending on sensors | Excessive draw or short to power |
Code P0653 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0653 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.