All Wheel Drive Problems?

Learn to Diagnose Why Your AWD Isn’t Working

So you’re having all-wheel drive problems? C0407 sym64 on your OBDII is a code that is stored in the rear differential clutch control module (CCM) when the all-wheel-drive oil pump starts slipping due to low oil. Oftentimes, the code appears after diagnosing the “service rear axle” message on the dash. It can cause the all-wheel-drive system to become disabled. 

When this happens, you’ll only have power going to the front wheels. You’ll need to trace the problem before you try to fix it. From where the transfer case connects to the front axle shafts, you have a driveshaft that goes to the rear of the vehicle. It connects to a rear differential which then connects to the axle shafts that power the rear wheels. This is as good of a place as any to start when diagnosing all-wheel-drive problems.

The rear differential assembly has two sides. One side has the clutch and the other the rear differential. The two are separated by a seal. Depending on the type of car you drive, the rear differential clutch control module is located right next to this assembly and is mounted to the differential clutch pump. 

Once the control module receives a signal that the rear axle is engaged or disengaged, it activates or deactivates the pump to control the delivery of hydraulic oil pressure. 

Ideally, the rear differential clutch control module will deactivate the clutch pump motor when the pressure reaches about 464 psi. This is when the appropriate system pressure has been reached. It then activates the differential clutch pump when the pressure goes below 392 psi. You’ll get a C0407.64 code when the oil drops below its recommended level.  

Possible Symptoms of All-Wheel-Drive Problems

The most common symptoms include:

1. Service Rear Axle warning message
2. Service Engine Soon warning light or check engine light
3. Anti-Lock Brake System warning light

Causes of C0407 Code

There are a couple of reasons why the differential clutch fluid could be low. They include: 

1. An external leak on the differential clutch
2. Oil leaking from the differential clutch and into the rear differential 
3. Improper filling during a pump replacement or gasket service
4. Bad differential clutch pump

How to Diagnose and Fix C0407 Code

The differential assembly should always be properly filled. When filling it with fluid, it’s important to note that the rear differential side is separate from the differential clutch side. The two use different types of fluid.

The rear differential comes with a drain plug and fill plug that you can use to refill the oil. All you need to do is remove the latter and then remove the former to drain the existing fluid. Once done, you’ll need to screw the drain plug back in and add some new oil through the fill plug. This fix applies when you’ve confirmed that the fluid is indeed low. However, if you remove the fill plug and notice that the fluid level is fine, you can move on to the differential clutch. 

In certain situations, you may see gear oil coming out of the fill plug when servicing the rear differential. This often means that the seal that separates the differential clutch from the rear differential has failed. A bad seal causes fluid to move from the former to the latter, hence, the reason why you’ll find gear oil coming out of the fill plug. 

The differential clutch comes with a level plug from where you can check the level of the clutch fluid. You should not use it to add fluid. If you do, the oil will not reach all the areas of the differential clutch. 

You’ll need to remove the vent hoses first to add fluid to the clutch assembly. A C0407 code occurs mostly when the pump is unable to pump fluid into the clutches to engage them. The fluid could be low or you could be simply having a bad pump. 

Once you’re done topping fluid in your differential, start the engine and let your car sit idle for five minutes in Park. You’ll need to push the accelerator to wide-open throttle five times to purge the air out of the pump. Once you’ve completed this process, shut the vehicle off and check the fluid level again. 

Have a drain bucket just below as you remove the level plug on the differential clutch. If no fluid comes out, you’ll need to add some through one of the vent hoses again. Having a rubber hose that you can install where the vent hose goes and a fluid transfer gun makes the work easier. 

This should help fix your code C0407 problem. Remember to check your fluid again after driving a few thousand miles. If it still runs low, you may need to replace the seal. 

Articles Related to All-Wheel-Drive Problems

• Clunking Noise When Turning the Steering Wheel?
• Too Much Play in Your Steering Wheel?
• Got Wheel Wobble? Test for a Bad or Noisy Wheel Bearing
• Whining Noise When Turning Steering Wheel? [Diagnose & Fix]