Suppose a pressure sensor is supplied with a perfect 5.00 V reference but its ground sits 0.30 V above true battery negative because of resistance in a shared ground path. The sensor and ECU may no longer agree on what the signal voltage means. The reported pressure can drift without the circuit ever becoming fully open.
This is why a continuity beep is weak evidence for a ground. Continuity mode uses very little current. A corroded terminal can pass that tiny test current while developing a significant voltage drop in operation. Measure voltage between sensor ground and battery negative or the specified module ground while the circuit is powered and working.
Be careful with measurement references. A signal measured against battery negative can look different from the same signal measured against the ECU’s sensor ground if there is ground offset. Understanding which reference the ECU uses helps explain otherwise confusing readings.
Repair the ground path rather than adding random jumper wires that may bypass designed current-sensing or ground architecture.