I recently bought a CX plus 4 and had an issue with the Overseer warning illuminating with no effect on the car and then disappearing on restart. There was little guidance in the handbook about the function or operation of this rather oddly named device. I took the car to Morgan and a module was replaced curing the fault. I was unable to find anyone who could explain the function of this device to me but the factory have sent me this explanation below which I thought might be of interest.
Why the Overseer is fitted?
Our ECU and Engine suppliers both stipulate that for safety reasons that there must be a way of monitoring un-intended acceleration in the event that an engine ECU malfunctions. This is in accordance with Automotive Safety Integrity Level (ASIL) as defined by the ISO 26262 Functional Safety for Road Vehicles standard.
Our supplier also stipulates that for automatic vehicles the vehicle must detect rear wheel lock-up, which is designed to prevent damage to the automatic transmission, driveline and engine in the event that the rear wheels are locked.
How does the Overseer work?
The Overseer is fitted behind the dashboard in the centre line of the vehicle. The Overseer has two accelerometers built inside the module which monitor the X and Y axis of the vehicle (left to right/up and down). These sensors are calibrated in the Overseer with the diagnostic tool with the vehicle on flat level ground. Once calibrated correctly, both accelerometers will read zero.
The throttle pedal in the vehicle is connected to both the Overseer and engine ECU. The Overseer is also connected via a CAN network to the engine ECU.
The Overseer is constantly monitoring the X and Y axis accelerometers and the throttle pedal. In the event that the Overseer detects the vehicle accelerating via the X and Y accelerometers and see's that there is no throttle pedal input from the driver, the Overseer assumes this is an un-intended acceleration event. The Overseer instantly sends a shutdown request via the CAN network to the engine ECU which shuts down instantly, resulting in the engine cutting out stopping the un-intended acceleration. If this does happen a fault code is stored in the Overseer.
To prevent rear wheel lock-up, the Overseer receives information via the CAN network on each individual wheel speed. The Overseer monitors the front wheel speeds and compares them to the rear wheel speeds. If there is a great difference in speed comparing the front wheels to the rear wheels (which are locked) the Overseer sends a command to the automatic transmission via the CAN network which instantly puts the automatic transmission in neutral preventing any un-wanted damage.
Why does my Overseer light come on?
Due to the Functional Safety requirements, the Overseer must warn the driver in the event of an issue. The Overseer is required to store individual fault codes for each type of failure. The Overseer accelerometers sometimes do require recalibrating and often this is the cause of the warning light illuminating. Re-calibrating the sensors on a flat level ground with the diagnostic tool will clear the warning light.
