This could be caused by several things, including:
* Low transmission fluid: Check and top off the transmission fluid if necessary. Low fluid is a common cause.
* Transmission fluid contamination: Dirty or burnt transmission fluid can cause issues with shifting. A fluid and filter change might be needed.
* Worn clutch pack: The clutch pack for first gear may be worn out or damaged. This requires a transmission repair or rebuild.
* Problems with the transmission's valve body: The valve body controls the fluid flow to the clutches and bands. Internal damage or a malfunctioning valve can cause incorrect gear ratios.
* Faulty transmission speed sensor: An inaccurate reading from this sensor can lead to incorrect gear selection.
* Internal transmission damage: More serious damage within the transmission itself could be the culprit.
This is a serious code and should not be ignored. It's recommended to have a mechanic diagnose the specific cause before driving the vehicle extensively, as continuing to drive with a transmission problem can cause further damage.
