Pontiac G5 RPM fluctuations and speedometer malfunction with transmission jolts on Pontiac G5

Some Pontiac G5 owners report experiencing RPM fluctuations and transmission jolts, which may be linked to issues with the vehicle speed sensor (VSS). These fluctuations during acceleration, accompanied by engine noise changes and a struggle to accelerate, can indicate a faulty VSS that affects transmission shifts, ABS, cruise control, and speedometer accuracy. Additionally, some owners find that speedometer malfunctions stem from a broken speed sensor or electrical issues. Vacuum leaks are also reported as common causes of RPM fluctuations, particularly when the vehicle is in Park, leading to an imbalance in the air-fuel mixture. In certain cases, a malfunctioning speedometer may trigger a P0722 code in the powertrain control module (PCM), potentially due to coolant contamination affecting the speedometer gear. Furthermore, some owners note that fluctuations in the speedometer can be alleviated by applying white lithium grease to the cables, although this may not resolve the underlying issues. It is crucial for owners to diagnose these problems promptly to ensure effective resolution.