Hydraulic Fluid Pressure/ Flow Circuit Short to Vbatt
The brake or suspension control module is detecting too much electrical voltage in the hydraulic pressure sensor circuit, like a wire touching the positive battery terminal. This short-to-voltage condition prevents proper pressure monitoring and can disable critical safety systems.
The ECU monitors the hydraulic pressure sensor output voltage, which should vary between ground and 5V based on actual system pressure. When the circuit shorts to battery voltage (12V+), the ECU detects an out-of-range high signal that exceeds normal operating thresholds. This triggers a fault because the sensor reading becomes unreliable for safety-critical calculations.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Pressure Sensor Voltage | 0.5V to 4.5V (varies with pressure) | Above 5.5V or sustained 12V signal |
| Pressure Signal Validity | Responds proportionally to brake/suspension demand | Constant maximum voltage regardless of system state |
Code C1420 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.
Once the fault is repaired, C1420 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.