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O/D Light Flashes

A very common question amongst owners of the Scorpio, particularly when they experience a gearbox problem is "What does it mean when the O/D light flashes?"

Strictly speaking, the Overdrive switch does not control an overdrive at all. It is simply an electrical switch that forces the EECV PCM to shift from 4th gear to 3rd, to provide more engine torque for overtaking, etc. The fact that it flashes at all is not documented in the Handbook (Pages 8, 45 & 90)

The OD light is controlled by the PCM, not the OD switch on the gearchange lever, and it is the PCM which turns on the light. It follows that, if the PCM detects a problem with the A4LDE gearbox, which is fully electronic, then it can blink the OD light. Further research has shown that the following fault conditions may cause the PCM to blink the OD light as a malfunction warning.

P0712 Transmission Fluid Temperature Sensor A Circuit Low Input

P0713 Transmission Fluid Temperature Sensor A Circuit High Input

P0717 Turbine/Input Shaft Speed Sensor A Circuit No Signal

P0718 Turbine/Input Shaft Speed Sensor A Circuit Intermittent

P0721 Output Shaft Speed Sensor Circuit Range/Performance

P0722 Output Shaft Speed Sensor Circuit No Signal

P0731 Gear 1 Incorrect Ratio

P0732 Gear 2 Incorrect Ratio

P0733 Gear 3 Incorrect Ratio

P0734 Gear 4 Incorrect Ratio

P0740 Torque Converter Clutch Solenoid Circuit / Open

P0741 Torque Converter Clutch Solenoid Circuit Performance Or Stuck Off

P0753 Shift Solenoid A Electrical

P0758 Shift Solenoid B Electrical

P0763 Shift Solenoid C Electrical

P0768 Shift Solenoid D Electrical

P0781 1-2 Shift

P0782 2-3 Shift

P0783 3-4 Shift

P0794 Intermediate Shaft Speed Sensor A Circuit Intermittent

P1502 Vehicle Speed Sensor Intermittent

P1700 Transmission Indeterminate Failure (Failed to Neutral)

P1702 Transmission Range Sensor Circuit Intermittent

P1713 Transmission Fluid Temperature Sensor In Range Failure (< 50 deg F)

P1718 Transmission Fluid Temperature Sensor In Range Failure (> 250 deg F)

P1727 Coast Clutch Solenoid Inductive Signature

P1743 Torque Converter Clutch Solenoid Circuit Failed On

P1751 Shift Solenoid A Performance

P1754 Coast Clutch Solenoid Circuit

P1756 Shift Solenoid B Performance

P1761 Shift Solenoid C Performance

P1766 Shift Solenoid D Performance

P1767 Torque Converter Clutch Circuit

P1783 Transmission Overtemperature Condition

This research has not proved conclusively that this is the case because it is not documented directly for the Scorpio, but last year, the List discovered that cleaning the MAF can affect the operation of the gearbox. One owner reported that he had been notified of a Solenoid Shift C error by a connection with the Ford diagnostic system WDS after his OD light flashed, and sure enough, on the list above, the DTC P0733 records such an error. 

During Diagnostic checks using the OBD lead and the Vehicle Explorer software we would expect to find one of the above DTCs in PCM memory after the OD light flashes.

NOTE: these actuators and sensors are mostly checked by the Comprehensive Component Monitor, not the OBD Monitors, although some, like the VSS, must be checked and verified in order for the OBD tests to be completed.