Hypovolemic shock: This is the most likely diagnosis given the patient's presentation with low blood pressure (90/56), tachycardia (P 116), and evidence of external injuries (chest and abdominal bruises) which could lead to significant blood loss. The fact that the patient is fully resuscitated and investigated suggests efforts to address potential hypovolemia.

Cardiac tamponade: The increased JVP (jugular venous pressure) and faint heart sounds could suggest cardiac tamponade, especially in the context of a motor vehicle collision which could cause traumatic injury to the heart or pericardium.
Cardiogenic shock: Although less likely given the context, cardiogenic shock could be considered if the patient had a pre-existing heart condition or if the collision caused a direct injury to the heart leading to pump failure.

Cardiac tamponade: Again, mentioned here because it's critical not to miss this diagnosis. Cardiac tamponade can present with similar signs (hypotension, tachycardia) and requires immediate intervention.
Tension pneumothorax: While not explicitly listed among the choices, it's a condition that could present with similar symptoms (hypotension, tachycardia, decreased breath sounds) and is a life-threatening emergency that needs to be ruled out, especially in the context of chest trauma.

Spinal shock: This is less likely given the patient's presentation. Spinal shock typically follows a spinal cord injury and presents with hypotension, bradycardia, and decreased peripheral resistance, which doesn't fully align with this patient's tachycardic response.
Neurogenic shock: Also less likely, neurogenic shock could be considered if there was a significant spinal cord injury, but the clinical presentation (hypotension, bradycardia) and the context provided do not strongly support this diagnosis as the primary concern.