The diagnostic module tank leakage pump, or DMTL pump, is a vital component of the evaporative emission control system found in modern vehicles. This part is responsible for preventing gasoline vapors from the gas tank or other parts of the fuel system from escaping the car and entering the atmosphere.
BMW first started using this technology in 1998. When the leak detection pump discovers a problem, it causes the check engine light on the dashboard to illuminate. A diagnostic scanner will generate a P1449 code.
Since laws demand leak detection pumps to monitor vehicular emissions, it is essential to get P1449 code help when it is needed.
P1449 Code Help
The P1449 code gets triggered by three possible causes. The harness for the diagnostic module tank leakage (DMTL) pump is shorted or open, the DMTL circuit has a poor or nonexistent electrical connection, or the part itself has become faulty. Repairing the issue is necessary to clear the code.
A DMTL pump detects the presence of vapor leaks along any point of the fuel system. It works with the overall emission control system to collect the vapors in charcoal canisters before reintroducing them to the combustion chamber.
The pump uses several components to create results, which means each one could be responsible for the P1449 code. A thorough review of the one-way valves, vacuum solenoid, vent valve, sensors, and the main diaphragm is necessary to ensure the pump works as expected.
An engine vacuum is used to move the diaphragm in the pump to determine if a leak is present in the system.
When pressures reach a specific limit, diaphragm movements stop, shutting the vent valve at the bottom of the unit. This activity seals the system to avoid pressure loss.
The vehicle’s ECU constantly monitors the movement frequency of the diaphragm since it only moves when pressure changes occur.
If this activity occurs, the check engine light appears on the dashboard. Any changes in this reading indicate a leak exists.
Depending on the pressure drop, the computer determines if the leak is large or small to issue the appropriate code.
How Can I Tell if the DMTL Pump Is Failing?
There is no way to tell if the DMTL pump is on a path to failure. The only way you’ll know that something is wrong is when the check engine light appears with the P1449 code.
This information lets you know that the pump failed, so it can no longer monitor for potential leaks in the fuel system. That means the vehicle won’t pass an emissions test, so a repair is immediate.
Although a check engine light can mean multiple things, you can run a bench test to determine if the DMTL pump is responsible for the problem. You’ll need the following items to run that operation successfully.
- A steady vacuum source.
- Jumper leads that connect to the DMTL pump.
- A 12V power source that activates the pump’s solenoid.
- One latex balloon to fit over the pump’s canister.
- Lift or jack stands.
Some BMW models have this part behind the rear wheel of the driver’s side, but it is typically found behind the passenger back wheel.
Once those components are available, you’ll be ready to test why your vehicle developed the P1449 code.
What Are the Vehicle Emissions Standards?
Vehicle emissions standards are set through a combination of state and federal legislative mandates in the United States. A similar process outlines these requirements in other countries.
All vehicles operated on roadways must meet the current published standard according to a testing scheduled outline in that legislation. Unless a specific make and model is exempted, these rules apply to all cars, trucks, and SUVs in the light-duty category.
It doesn’t matter if you use diesel, gasoline, or E85 fuel in the vehicle.
You can see the environmental ratings for new vehicles on the label. This information is underneath the greenhouse gas (GHG) rating. It reflects carbon dioxide emissions, which are responsible for approximately 99% of what escapes from the tailpipe.
Automakers certify their vehicles to meet the current smog rating standards in the United States. They’re called “bins.” The fleet must meet a specified average to comply with the current legislation.
If a vehicle receives certification to a specific bin, it cannot exceed the specified amount.
Different tiers are assigned to designate the various bins and standards. When a BMW experiences DMTL pump failure, it can exceed the certified standard set for it with the current emissions standards.
If your vehicle doesn’t pass an emissions test, it might not be possible to register it. You’ll receive a report from the inspection station that details the necessary repairs. It needs to be presented at the shop after fixing each problem to prove the concerns were properly addressed.
Some vehicles may be eligible for waivers after a second test, but you might have additional expenses to pay. Illinois allows this option after spending at least $450 on related repairs.
How to Test the DMTL Pump in My BMW
You’ll need to remove the DMTL pump from the vehicle to test its leak detection capabilities. Here are the steps to follow to take care of this task.
- Disconnect the negative terminal from your vehicle’s battery to prevent electrical discharge or damage while working.
- Lift the vehicle with an appropriate jack. You can also drive up a secured ramp or work underneath in a designated bay. Don’t work on this project if the only thing holding up the car is the jack.
- Once the vehicle is secured, remove the plastic panel from behind the rear wheel. You’ll have access to the EVAP canister and the DMTL pump at this step.
- A couple of vacuum lines should be connected to your pump, electrical connector, and canister. If they are not, this issue could be the reason for the P1449 code. Reconnect, replace the cover, and clear the code. If your vehicle functions without the check engine light, you can stop here. If not, continue to the next step.
- After disconnecting the vacuum lines, you’ll see that the pump is connected by a few screws to the canister end. You may need a Torx head to remove them. Once the hardware is gone, you’ll have disconnected the pump from the canister.
Once you reach this point, you can bench test the DMTL pump to see if it is functional. You’ll attach the jumper cables to the pump’s power source and connector. The vacuum source gets connected next, then cover the canister side with the balloon.
Once the testing setup is secure, you’re ready to turn on the power source. Flip it off right away, then repeat to mimic how the engine vacuum operates. This action will cause the balloon to start inflating.
If the DMTL pump is working as expected, the balloon should stop getting bigger about 30 seconds into the bench test. Stop giving power to the system to see if the balloon starts reducing in size. Should that result occur, you have evidence that a leak exists, and the pump requires a replacement.
Can I Drive with a Faulty DMTL Pump?
Your vehicle can drive with a faulty DMTL pump because the emission control system doesn’t play a role in how the engine functions. The equipment only operates after turning the engine on or off. It checks for vapor issues, not a fuel leak.
Any check engine light issue should be reviewed to ensure there isn’t a severe issue occurring that requires a significant repair. If you’ve narrowed the problem to the DMTL pump, no further damage occurs. You just won’t pass an emissions test.
What If I Get Other Codes When Testing the DMTL Pump?
The AUTOPHIX 7910 Enhanced BMW Diagnostic OBD-II Scanner is an essential tool to use when diagnosing potential problems with your vehicle. It gives you diagnostics, service options, and a shop manager feature to let you find or clear error codes that cause the check engine light to illuminate.
You receive the benefits of an OBD-II scanner while having access to the codes generated by your BMW.
Most scanners, including ECU re-programmers, don’t provide this capability because of how unique they are with BMW systems.
When you plug the scanner into the vehicle’s port, the most common error code you’ll see is P1449. Some associated codes can also display when there’s a problem with your leak detection pump.
- P1447 displays when the DMTL pump is too high during switching processes.
- P2402 is an OBD-II code that lets the ECU detect that the emissions control systems have a voltage signal return that’s too high.
- P0456 appears when the ECU detects an emissions leak of 0.02 inches in the system.
- P0442 displays when the leak reaches 0.04 inches.
- P0455 is the OBD-II code you’ll see when a leak larger than 0.04 inches is present.
When it’s time to install a new pump or return one that passed a successful bench test, you’ll follow the removal steps in reverse. Check with your AUTOPHIX scanner to see if more codes appear, or if the P1449 code returns. If it does, you’ll need to investigate the situation further.
If not, you’ve successfully repaired your leaking DMTL pump.
When Are Emissions Tests Required?
Thirty-four states currently require emissions testing for vehicles. Anyone residing where testing doesn’t occur can drive with a faulty DMTL pump without worrying about enforcement. In the jurisdictions where testing is mandatory, it starts on the third year after the model year, and then two years after.
The P1449 code lets you know that a problem with the DMTL pump exists. It’s up to you to decide if you want to swap out the malfunctioning component for a new one.
When I had my pump stop working, the repair cost was more than what I could afford at the time. I decided to let it stay that way since my car drove the same.
What I noticed from that experience is that my fuel economy suffered. I dropped a good four or five miles per gallon, which meant the cost of letting the repair sit eventually caught up with me.
To save money, I decided to take care of the work myself. It took about three hours to do everything right.
Even though the car continued driving the same way, the fuel economy returned.
If you live somewhere that requires an emissions test, the DMTL pump needs to be repaired or replaced up to 90 days before your scheduled test. By taking the time to do this work now, you can prevent a bigger future headache.