We all dread seeing blinking lights on the dash.
If you’re out driving, a blinking or flashing light on the dash is scary and disruptive. On the positive side, it’s a sign that the vehicle needs your attention. So, what causes the overdrive light to flash, and how can you address the underlying problems?
The overdrive (O/D) light will flash due to low transmission fluid, overheated transmission fluid, defective O/D sensor, wiring problems, or a faulty O/D solenoid. Understanding the cause will save you a lot of time and money when resolving this issue.
Herein, I detail how to fix overdrive light flashing and more.
Question: What’s the Meaning of Overdrive Light Flashing?
The overdrive light should remain on or off while driving. If the light blinks, it indicates problems with your vehicle’s transmission.
The overdrive serves as the highest gear for a vehicle’s transmission. You can engage or disengage the O/D depending on a given road speed.
When you engage the overdrive, the light on the dash stays off, and the transmission shifts into high-gear mode. This increases the engine’s RPM (revolution per minute), and the car gains power. It’s a helpful feature when overtaking or driving uphill.
Conversely, the O/D light should be on when you disengage the overdrive. Disengaging the O/D lowers the engine’s RPM and lets you drive at a steady speed. You can use this feature when driving on highways to reduce fuel consumption and engine noise. A disengaged overdrive minimizes the wear and tear of your car.
Answer: How To Fix Overdrive Light Flashing
You can fix the overdrive light flashing issue by troubleshooting various problems with the transmission. Let’s see what you can do to resolve the underlying issues.
Add Transmission Fluid
A car’s transmission relies on adequate fluid to keep components functioning properly. Your car’s routine maintenance should include checking the transmission fluid level and refilling it as required.
If the fluid level is low, it’ll create low-pressure levels in the transmission. Low fluid pressure won’t activate the overdrive solenoid. As a result, the solenoid won’t trigger the O/D gear, causing the light to flash.
The good news is that this problem ends when you top up the transmission fluid. So, park your vehicle on a flat surface and check the fluid level. The dipstick marks should help you know if the fluid level is low.
Check the manual for the recommended transmission fluid. When refilling the reservoir, add the fluid in small amounts while checking the level. Overfilling the reservoir can cause excessive pressure build-up and damage the car’s internal components.
Repair or Replace the Overdrive Solenoid
The transmission system relies on the overdrive solenoid to activate the overdrive gear. The solenoid needs to be in prime shape to do the work.
If your car has a functional O/D solenoid, it’ll activate the O/D gear when needed to improve fuel economy, reduce noise and minimize engine wear. However, improper maintenance of the system can cause the solenoid to malfunction.
Electrical issues, low transmission fluid pressure, or dirty transmission fluid are to blame if the solenoid fails. A failing solenoid might not activate the overdrive gear, and the O/D light will start flashing. Moreover, the gear might shift erratically or fail to shift at all.
If you suspect the solenoid is the culprit, check and fill the fluid to the required level. Dirty or contaminated transmission can cause the solenoid to get stuck. Check the fluid for dirt or debris and change it with fresh fluid.
An experienced technician will diagnose the solenoid to determine the cause. Fixing the underlying issue might involve cleaning or replacing the solenoid.
Replace the Overheated Transmission
The engine needs to remain at the normal operating temperature to ensure everything works properly. However, it’s common for the engine to overheat due to inadequate coolant or other issues. When the engine overheats, it can increase the temperature in the transmission system.
An overheated transmission can cause severe damage to the seals, clutches, and other components. If you fail to resolve this problem, you might see the overdrive light flashing on the dash.
Before replacing the transmission, determine the cause of the engine or transmission overheating. Ensure the oil and coolant levels are okay.
The engine and transmission system have numerous moving parts that can overheat due to excessive friction. Check these parts and ensure they’re properly lubricated.
If the transmission keeps overheating, stop the vehicle and allow it to cool down. Then call your mechanic to replace the overheated transmission.
Clean or Replace the Overdrive Speed Sensor
Cars have sensors that monitor parts and send signals to the ECM. If the overdrive light is flashing, a dirty or defective speed sensor could be to blame.
The sensor monitors the overdrive transmission system’s operations. It measures the shaft speed and cruise control and communicates with the ECM. If dirt or debris lodges on the sensor, it will not monitor the transmission system.
As a result, the overdrive system won’t function optimally, and the O/D light might start flashing. Here’s how to fix overdrive light flashing due to a malfunctioning sensor.
Locate the O/D sensor in the hood beside the engine. If it’s dirty or lodged with debris, use a microfiber towel to clean it. Then spray the towel with a degreaser and gently clean the sensor. Cleaning won’t fix a faulty sensor, so replace the sensor if it’s defective.
Replace Worn or Damaged Wires
The transmission system relies on several wires to transmit signals to the ECM. Over time, these wires break, melt, or corrode, causing the overdraft system to malfunction and flash the light.
Burnt or frayed wires can create electrical shorts and damage various electrical components. Address a wiring problem in your car as soon as you spot it.
In this case, you’ll need to locate the wire harness in the engine compartment. The connections must be secure. Otherwise, they won’t transmit signals as expected. If the wiring harness is worn or corroded, replace it.
An auto-electrician can help you test the wires and replace the defective ones.
Replace the Transmission Filter
If dirt or debris finds its way into the transmission, it can cause severe damage to the system. That’s why the transmission system has a filter to keep the fluid clean. Its role is to catch dirt, metal shavings, or any other particle that might get into the system.
But like any other vehicle component, the transmission filter can wear out or become damaged. A damaged filter will let in dirt and metal shavings into the system. As a result, the filter gets clogged over time and blocks the fluid flow.
A dirty or worn filter will eventually damage the overdrive system and cause gear slipping problems. With time, you’ll start seeing the overdraft light flashing while driving.
It’s advisable to inspect and replace the transmission filter regularly. Luckily, replacing this filter is straightforward and inexpensive. You should also change the transmission fluid if dirty.
Bottomline
We hope you now understand how to fix overdrive light flashing. Start by determining the root cause to get an idea of what you’re dealing with. Usually, the overdrive light will blink due to low transmission fluid, a defective solenoid, overheated transmission, or a faulty sensor.