On my way home back from work, all of a sudden, the overdrive light on my Ford F-150 starts blinking with the hard shifting of gears.
I somehow managed to reach home and contacted Ford Service Centers regarding the problem. They informed me that overdrive light flashing is an indication of a problem in any parts of the truck’s transmission system, and they need to run an onboard diagnostic tool (OBD) to identify the fault codes.
What does Overdrive Light Flashing on a Ford F150 Mean? In general, Overdrive light flashing on a Ford F150 means an electrical or mechanical fault in the transmission system. Check the relevant fuses and wires as a first step. Next, use the OBD reader to identify the faulty parts and take remedial action accordingly.
I will share my experiences regarding possible reasons for overdrive light blinking and how I have been able to identify and resolve the fault in my truck.
What does Overdrive Light Flashing on a Ford F150 Mean?
Overdrive is a mechanism in all auto and manual transmission vehicles that allows it to achieve a certain speed with lesser RPM of the engine.
They realize it with the help of a transmission system with larger gear on the side of the transmission system connected with wheels.
Therefore, it allows it to attain higher speeds with the engine turning slowly, resulting in better fuel economy.
It’s repeatedly blinking means any problem in the transmission system of your pickup truck.
Problem in Transmission
Overdrive is a part of the truck’s transmission system, and any problem in its gear train can be the reason behind the blinking of this light.
Ford authorized dealers or service shops to identify the fault using diagnostic tools and often rebuild the transmission.
Rebuilding requires cleaning all moving parts, replacing worn-out or broken gears, and replacing all seals and gaskets.
Blown out fuse
There are multiple fuses connected in Ford F-150 with various relays feeding power to the PCM, overdrive switch, and solenoids in the transmission system.
If, for some reason, there is any short circuit in any part, the fuse blows out as a safety measure.
Therefore, you should check for the relevant fuses with the transmission system and look for any of them burnt.
However, you should also check for the path of the blown-out fuse to find the faulty components.
Rusty/burnt wiring or lose connection
There are multiple wires from solenoids, speed sensors, and temperature sensors in the transmission system to the transmission control module in PCM.
Over time, any of them gets rusty or loose from its connector. Due to wires underneath the truck with all moving parts and dirt all around, there are many chances of a broken wire.
All these scenarios result in loss of signal or faulty signal to the control module.
Therefore you will see blinking overdrive light to indicate a fault signal from PCM. Check for the wires and replace them if you find any of them faulty.
Problem in the filter of transmission fluid
The transmission filter aims to remove the debris and pollutants in the fluid entering the transmission chamber.
These filters have magnets to capture metallic parts. In case of a faulty or expired filter, debris and metallic pollutants cause heating of the transmission system and harsh gear shifts.
Therefore, you will get an overdrive warning sign blinking. You should check for the filter and fluid condition and change or flush it to resolve the problem.
Low level of transmission fluid
Transmission fluid lubricates and removes heat from parts of the transmission system. Any leakage in the transmission chamber causes oil to leak.
Low oil level damages the gear surfaces, their heating and creates noisy operation.
Therefore, check the transmission fluid for any leakage. In case of a too low level, replace the seals and add the transmission fluid to the required level.
High temperature of transmission fluid
I have found two reasons for the transmission fluid temperature errors. First is too high or too low temperature of the fluid due to any mechanical faults or its low level.
Too hot or too cold weather can also be a factor to consider. The second is a faulty temperature sensor that is either a grounded or short circuit in its circuit.
Its symptoms are noisy operation, vibration, and hard shifting. In either case, remove the root cause and resolve the issue.
Problem in transmission solenoids
Transmission solenoids are electric valves to control fluid flow in chambers of the transmission system during gear shifts.
They develop faults like open or short-circuiting of their coils. It results in a blinking of this light. Its symptoms are that you get stuck in a single gear or hard shifting.
You should check the error code during diagnosis and replace the faulty solenoids.
Problems in speed sensor
Speed sensor has an essential role in automatic transmission as it sends an electric signal to the transmission control module in PCM for necessary shifts according to speed.
The same sensor also sends information to the speedometer to display the speed of the truck.
If it becomes faulty and sends the same signal to transmission control, you will see an overdrive light flashing on your truck’s dashboard.
In case of a defective part, you will need to replace it by spending $20-$30.
Faulty Range Sensor
Range or position sensor sends the position of transmission shifts to the PCM for its correct movement.
Its symptoms are harsh shifts, or you can get stuck in initial gears.
Faults in other Sensors
Other sensors in the truck are not part of the transmission system, but their malfunctioning can result in such an issue.
They are mass airflow sensors, output shaft sensors, torque converter clutch, and electronic pressure control sensors.
Their symptoms are hard shifts, slipping, vibrating lockup, and noisy operation. Again, check the error code to find the cause behind the problem.
How to identify and resolve the Ford F150 overdrive light flashing problem using OBD?
Overdrive flashing can be a result of malfunctioning of various parts in transmission and auxiliary systems.
However, to identify the specific part creating the problem, you need an onboard diagnostics reader to read fault codes.
You can purchase it yourself or visit a truck mechanic or Ford Authorised Dealer to avail of their services. After connecting the OBD reader, you will find a single or a list of fault codes.
Each fault code has a specific meaning related to the problem in your Ford F-150. You will find the explanation of those codes in the service manual of your truck.
Once you identify the faulty part, go to the workshop to replace that part. In case of multiple faults, you will need to rebuild the transmission involving complete servicing and replacement of faulty components.
However, as per my experience, the problem is not in the parts indicated by the fault codes.
Mostly it is a simple one as a result of bad wiring or a blown-out fuse.
Therefore as an initial step, you should check the fuses and wires yourself before visiting the workshop or running OBD tools.
How much does it cost to fix it?
It is vital to inspect your pickup truck as soon as you get an overdrive flashing light.
If you keep on driving it with a blinking warning light, it will result in further damage to the transmission system requiring its complete rebuild.
Replacement of a faulty part or sensor will cost you only $20 to $30, but a complete transmission rebuild requires you to spend $2000 to $3000.