This article discusses what the blinking or flashing light on your dashboard signifies and what the possible causes for your 4 wheel drive to not engage. Strangely enough, this is a fairly common occurrence on most makes of 4 wheel drives but is not really a complex problem to troubleshoot.
So what is that 4 wheel drive indicator blinking on your dashboard means? The purpose of the 4 wheel drive light is to indicate when you have engaged 4WD mode by selecting 4H. When the light flashes continuously for more than 30 seconds it signifies there is a problem somewhere on your drivetrain system and that 4WD has not engaged properly. Once 4WD mode is engaged successfully, the 4×4 light will shine a solid color, usually orange or green.
Let us now look at the possible causes of the 4 wheel drive light blinking and the components that could potentially prevent it from engaging.
Why My 4-Wheel Drive light blinks but won’t Engage
First, let me relate a short experience. About two weeks prior to me writing this article I went 4 wheel driving with a few mates up in the mountains. Before we headed off to do the actual 4WD trail, we decided to test out this off-road playground with a few obstacles to get the guys warmed up a bit and test that all our 4 wheel drives are in good working order, diff lockers and all.
Everything as going fine until my mates very capable 4×4 failed to clear an obstacle I cruised over with ease. Now, the reason I thought this was odd was that his 4WD was kitted with a suspension upgrade and bigger tires and it has low range with diff lockers.
He then signaled to me to come to have a look since his truck was behaving strangely. Low and behold the 4 wheel drive light was simply flashing on his dashboard. What was wrong? He’s 4WD failed to engage properly! But why?
Let’s look at a few of the usual suspects.
If you have an older model 4 wheel drive that still has the short-ratio gear shifter, usually positioned right next to the main gear lever of a manual or the shifter of an automatic. The function of the short lever was to engage 4WD mode as well as 4-Lo. The 4-Lo engaged the low-range transfer case for rough and challenging off-road driving.
Fast forward a few decades and, enter the Actuator. The actuator is a component found mostly on modern four wheel drives and is designed to electronically engage 4 wheel drive. It accomplishes this by means of a small electric motor bolted onto the transfer case that shifts a pin in place to lock the center transfer differential.
The actuator allows you to shift from 2WD to 4WD on the fly and back to 2WD without stopping and can be engaged and disengaged by means of a switch inside the cabin, usually on the dashboard. The actuator can be activated electrically or with the use of an air vacuum system. The beauty of this device is that negates the need for the driver to stop the vehicle, having to get out, to manually engage the vehicle into four-wheel mode by locking wheel hubs. Hooray for technology!!!!
So now that we know the function of the actuator, it makes sense that when you press the 4WD or 4H button on your dashboard, and the 4WD light just flashes, that the possible cause could be the actuator motor, internal gears inside the motor or the actuator electronic module.
The Rear Diff Locker
This is another culprit that could result in a flashing 4WD signal on the dashboard. This signal might be red in color instead of orange. This happens when you are in 4WD 4Lo (Low range) mode and you want to engage the rear diff locker. The rear diff locker also uses a type of electric actuator to engage the locker inside the differential. The rear locker is used under challenging off-road situations where you require maximum traction on as many wheels as possible.
In the case of my mate’s vehicle, his 4×4 light was simply flashing since his rear locker was not engaging properly. I asked him if I could drive to have a look at what was wrong. I reversed a bit, moved forward a bit but still no solid light. I disengaged the switch and tried a few more times. Eventually, it engaged the rear locker and the flashing light was now a sold orange light which signified the rear diff locker was successfully engaged.
So this could be a second possible culprit as to why you are seeing a 4WD light blinking on your dashboard. Sometimes the locker motor gets jammed due to grime, mud or lack of lubrication and it takes longer than usual to engage. Try driving forward and backing up a few times to assist it to activate. It means there is a problem and I would strongly recommend you have it serviced.
What does the 4WD light on the Dashboard signal?
So we’ve established that it could signal one of two possible causes:
- Your 4WD actuator is faulty
- Your rear diff locker failed to engage
Remember, the rear diff lock scenario is only applicable if you are already in 4WD 4Lo mode and you attempted to activate the rear locker and the light starts to blink continually.
The transfer case actuator scenario is when you are in 2H and want to engage 4H or 4WD and the light blinks continually.
Let’s now look at other reasons why your 4WD fails to engage.
The Transfer case
The transfer case could pose another reason why your 4 wheel drive fails to engage. This could be due to the vehicle not coming to a complete stop to allow it to engage. This is because the splined pin and gears of the actuator need to align 100% with the gears inside the transfer case. If they cannot align properly or becomes a bit sticky you will get the flashing 4WD light on the dashboard.
Now I know most manufacturers will boast about “shift on the fly” into 4WD mode blah blah, I would recommend you proceed with caution with your expensive trucks. It takes only a few seconds to stop the vehicle if the 4WD is not engaging, make sure you are in neutral and allow for up to 15 seconds for it to engage, then you may proceed safely in 4WD.
Another reason 4 wheel drive does not engage could be due to high oil temperatures inside the transfer case, causing 4WD not to engage. This could be caused by heavy load on the box for extended periods. Possible scenarios could be any of the following:
- Towing a heavy trailer or boat on thick beach sand
- Heavy off-roading for extended periods
- Pulling a heavy boat
Any scenario where you are in 4 wheel drive and the vehicle is under constant load for a long period.
A fourth and final reason why your 4 wheel drive light is flashing and 4WD fails to engage could be due to a faulty signal. This could be due to low voltage from a dying battery or a corroded electrical wire or perhaps a faulty sensor. Could also be a faulty switch on the dash or a blown fuse. These are possible culprits of a modern 4 wheel drive system:
- Failed Actuator
- Dirty actuator connector
- Low Battery voltage
- Corroded electrical wire
- Faulty sensor
- Faulty dashboard switch
- Blown fuse
Next, let’s look at a few real-world scenarios with vehicle-specific solutions.
4 Wheel Drive light Flashing on your Chevy?
The next extract is from gm-trucks.com where the user describes exactly what we’ve been discussing.
I have a 1996 GMC 1500 Sierra 4 x 4 Pickup with the push button 4 wheel drive. When I push the 4 wheel high or 4 wheel low button the light on the switch just blinks. It is not going into 4 wheel drive. Where do I start looking for the problem? I don’t want to just start swapping parts. Thanks,gm-trucks.com
Possible Fault-finding Solution:
- Leave the ignition on.
- Make sure the transfer case is in 2Hi
- Make sure the transmission is in Neutral
- Check if the front driveshaft can rotate. It should be able to rotate in 2H
- Engage 4H
- Check if you can rotate the front driveshaft. It should not be able to rotate
- Leave the transfer case in 4Hi and jack up the right front tire.
- The front right tire should be able to rotate.
- Next, Switch off the engine.
- Disconnect the 2 wires that plug into the actuator motor
- Spray the connector with a dielectric spray and reconnect the wires back up.
- Get somebody to turn the ignition on and select 4WD.
- If the actuator does not move, it’s dead.
- Test for voltage at the wires. If you have voltage, and the actuator has failed
Follow this simple procedure to isolate the actuator problem. Next, let’s look at an example of 4WD flashing on a Dodge Ram.
4 Wheel Drive Flashing on your Dodge Ram?
The following is an extract taken from dodgeforum.com where a user complains about his 2011 dodge ram 4WD light flashing without engaging 4WD.
My 4wd light flashes and won’t stay constant lit. Seems as though the 4wd is engaged. Anybody know anything about this? It is a 2011 Ram. Thanksdodgeforum.com
The Dodge Owner’s Manual explains the shifting procedure and gives specific instructions on how to do it. It mentions the following:
- The transfer case neutral position needs to be selected before you attempt to engage 4WD.
- The selected position indicator light will flash until the transfer case completes the shift.
- When the shift is complete, the indicator light for the selected position will stop flashing and remain ON.
- If any of the shift conditions are not met, the indicator position light will continue to flash.
- You cannot be in gear for it to work.
- If you don’t shift it into neutral, the 4wd light will continue to flash and won’t get into gear.
Seems to be a common occurrence on these trucks. Dodge dealers recommend engaging 4-lo, then back in 2-wheel drive, then back in 4-wheel drive hi (4H). This sequence apparently resolves the problem. Could be a faulty sensor causing the 4WD not to engage. Again, it is highly recommended to stop, put the transmission in reverse, go a few feet, stop, then back to drive.
4 Wheel Drive Flashing on your Jeep Liberty?
So you might have a Jeep Liberty with 2H, 4H and 4Lo settings. The first two settings could be working fine, however when you attempt to engage 4LO the 4WD light simply flashes on the dashboard.
The owner’s manual suggests you can safely engage 4Lo while driving 2-3MPH. Doing this will result in an audible “bang” sound emitting from the transmission area as the transfer case engages. If you are driving above 5mph the transfer case cannot engage. It is highly recommended to bring your Liberty to a complete stop, place the transmission in neutral and then engage 4Lo.
Liberty drivers have expressed trying to engage 4Lo while rolling at 2-3 mph as the manual says you can. Many have reported hearing a big “clunk” or “bang” noise when 4lo engages while rolling, but no metal clunk sound when bringing the vehicle to a complete stop first and engaging neutral before engaging 4Lo.
I cannot stress this enough, read the owner’s manual for the specific selection instructions. In the instance when the manual states you can select under 5mph, it is always safer to make sure the vehicle is stationary first before you engage 4Lo. This is to allow the teeth on the spline that engages the low range gears inside the transfer case to line up properly first. Better safe than sorry.
There could be multiple reasons why your 4 wheel drive light on your dashboard is blinking and not engaging properly. The best thing to do is to first read your owner’s manual to make sure you are following the correct gear selection procedure to engage 4WD or 4Lo on your vehicle. If your sequence is correct and the light keeps flashing, you need to use the process of elimination.
Start with the smaller, cheaper items first like the 4×4 dashboard switch. Make sure that’s not faulty. Next, check for any obvious loose wires underneath the vehicle. Next, have a look at your actuator module. Try resetting it by removing the switch, giving it a spray with a multi-purpose dielectric spray to make sure the pins are making proper contact. That is usually the culprit in many instances. Sometimes it just needs a clean and service. Otherwise, if the actuator has failed, it will need replacement. The worst-case scenario is the teeth on the spline that engages 4WD in the transfer box has missing teeth or the gears are failing to align, meaning the box needs to be removed and repaired.