VW Passat Reset After Battery Change – Needed? We Explain

Volkswagen Passat is undoubtedly one of the most popular VW models. With an average of 500,000 Passats sold globally every year, one needn't look far into the reasons behind the car's popularity. With every turn of the year, VW makes tantalizing upgrades to the already swanky series of cars.

Dead car battery replacement highlights

• Critical voltage:less than 10 volts
• Average battery age:4-5 years
• Tools needed:set of wrenches
• Timeneeded:15 minutes
• If done incorrectly:electronic glitches, frying ECU, no crank-no start
• DIY fix:possible
• How much to fix?$150 - $250

What happens when you change your Passat battery?

Let us start with the basics. A car battery is bound to run out of juice after being used for a given period of time. The VW Passat is no exception, and after several years, the battery will become obsolete, and you will need to replace it.

The modern VW Passat is unlike the old ones produced in 1973. The modern Passat is equipped with a plethora of systems and technologies, all of which are meant to make the driver experience superb. The modern Passat, say one made in 2016, has unique features that enhance the battery's performance and others that limit how you handle a battery change.

When you remove the battery from the car, the computer and other parts that rely on the uninterrupted battery power will switch off. When you install a new battery, you will observe some systems, such as the clock, will be at the default setting.

Some crucial car parts that may malfunction or act weirdly include the immobilizer. Changing the battery can cause the immobilizer to lose synchronization with the car. Removing the old or dead battery usually wipes away the car's settings because of the disrupted voltage. Therefore, you will need to reset your VW Passat to avoid being locked out of your car or stranded.

Sometimes, after replacing a battery, the check engine light pops on the dashboard and stubbornly remains lit. This is a common problem reported by several Passat drivers on several online forums. Unfortunately, the check engine light might indicate that some part is malfunctioning and needs replacement or repair. But in most cases, the trick is to reset the Passat's ECM, and the check engine light will disappear.

When the time comes to replace the battery, some steps or procedures must be followed, albeit behind the scenes. The alternator is supposed to be disconnected in a specified way to avoid electrical malfunctions later when you install a new battery. When you replace the car battery, an alternator wrongly disconnected can affect the electrical systems, especially the charging system.

The alternator is responsible for properly operating the car's electronics once the engine starts running. While a bad alternator is unlikely to damage a new battery, it has been seen to kill batteries. This means a malfunctioning alternator can make the ECM and PCM malfunction after installing a new battery. This will require you to scan for trouble codes and repair whatever is damaged for the car to operate normally.

How to reset the VW Passat battery after battery change

A successful reset of the VW Passat after battery change requires proper disconnection of the old battery and installation of the new one. According to the Passat manual, the battery has been designed to suit your location and some safety specifications. VW insists you use only TL 825 06 and VW 75073 batteries, which should not be older than 2012.

If your Passat has the start/stop ignition button, the manufacturer insists that you only replace the old battery with another one of the same specifications. The manufacturer recommends that battery change be done by an authorized dealership to avoid damage to the battery and, more specifically, the vehicle systems. The battery change of a Passat with a start/stop ignition button is accompanied by an adjustment of the vehicle electronics, a process requiring the use of special tools.

How to disconnect the battery

• Start by switching off the electrical consumers and the ignition.
• Unlock the car to avoid triggering the anti-theft system.
• Disconnect the negative battery cable and then the positive cable.
• Installing the new battery. Ensure you install the terminals correctly; otherwise, the horn will blare until you correct your mistake. It is very dangerous to connect the battery terminals incorrectly.
• Switch off all electrical consumers, including the ignition.
• Connect the positive cable and then the negative cable.

Some indicator lamps and lights will normally appear when you install a new battery and switch on the ignition. These lights should disappear after you drive for a short distance at about 12 mph. The vehicle should be taken to a VW dealership when the indicator lights fail to go away.

How to reset your VW Passat after a battery change

• To reset your VW Passat after doing a battery change is easy when you have an OBD-II scanner. Because the car's computer gets disrupted when you remove a battery or when it dies, it needs to be reset to avoid issues with the anti-theft system or engine running.
• Keep the ECM powered to avoid resetting your Passat after a battery change. This ensures the ECM doesn't get wiped off all its memory settings. This is done by keeping the battery cables connected to a tender to avoid any disruption in voltage. A tender is a device that maintains battery charge for some time between removing an old battery and installing a new one. This helps avoid resetting the ECM or the fob key.
• In cases where resetting your VW Passat is necessary either because there are stubborn warning lights on the dash or the engine acts funny, you should consider consulting a VW mechanic. You may notice the check engine light is not going away even after a short drive, or the engine is switching off shortly after starting the car. Here are a few things to consider;
• Use the OBD-II scanner to establish what the problem is. In many such cases, the mechanic will simply press the 'reset' button on the scanner, and the ECM is reset. In other cases, there might have been a damaged part that needs to be repaired or replaced, and that's why the lights are not going away.

Is it necessary to reset your VW Passat after battery change?

This is a question that doesn't seem to have a definite answer, especially after listening to dealerships and reading VW Passat drivers' experiences. On the one hand, the dealerships and mechanics insist that there is a need for a reset every time you do a battery change. On the other hand, online videos and VW Passat user forums suggest otherwise.

If you own the older Passat, say the 2007 model, battery change is simple, and many drivers report not experiencing any issues. Many report of removing the dead or the old battery as required and installing the new one as recommended. After cranking the engine, you will see the 'steering locked' and the traction light appear on the dashboard. After driving for a short distance, these lights go away.

The procedure for newer models, such as a 2017 Passat, is pretty much the same as the older Passat cars, save for a few minor changes. The battery location for the newer models is different and hidden on the left-hand side of the car under the panels. Like the older Passat, your new Passat will display a 'steering lock' and traction warning lights alongside a low-pressure tire warning light. Driving your car for a relatively short distance will make these lights disappear.

When you remove your car's battery, there are bound to be disruptions in the ECM, the PCM, and other car parts that require a constant power supply. However, the modules in your Passat are intelligent and are designed to remember and store data. This makes it possible for the car to start and drive without issues, even after a battery change. Fewer are the times when you will need to reset your Passat after a battery change.

A reset of your VW Passat will, therefore, be necessitated by the behavior of your car after replacing the battery. If the 'steering lock' and the traction ABS warning lights appear and go away after a short drive, there is no need for a reset.

Conclusion

Changing the car battery in your VW Passat is very similar to that on many other vehicles. If you are keen on following the laid-out procedures, there is no need to panic when your car's battery dies. Replace the battery, and the car's ECM and PCM will automatically update themselves. There is no need to call a mechanic whenever you need to change or replace your car's battery. Investing in a budget OBD-II scanner will go a long way in helping you resolving small issues like car reset after battery change.