Audi A4 / S4 / RS4's Most Common Radio Code Causes
Many owners encounter security code prompts on their A4 / S4 / RS4 after electrical work.
Below are the most common situations when this can occur.
Battery Change Lock
When the battery is replaced, the Audi A4 / S4 / RS4 radio requests a security code.
This factory protection system is designed to prevent theft by disabling the radio after power loss.
Other Situations That Trigger a Radio Code on Audi A4 / S4 / RS4
- Installing a replacement head unit will require the original anti-theft code.
- After an ECU or software reset, the radio may enter security mode.
- A fuse removal can cause the Audi A4 / S4 / RS4 radio to lock.
- Jump-starting the vehicle can trigger anti-theft mode, requiring the unlock code.
The Radio Code - What is It and Why It's Important?
A radio code, also known as an anti-theft code is a security PIN that restores access to your car stereo after it has been locked.
This security code is triggered when the radio detects a power interruption.
Automakers include this feature to protect factory stereos from theft.
If power is cut, the radio stops functioning and requires the unlock CODE before it can function normally.
Once the valid numbers combination is entered, the stereo is fully reactivated.
Is Getting a Free Audi A4 / S4 / RS4 Radio Code Possible
Before you pay for it, you should check a few places where the code is often stored.
Some owners find their Audi A4 / S4 / RS4 radio code without needing any tools or paperwork.
Here are the most common things to check first.
Check the Car and Its Documentation
- In the radio manual, often on a sticker page.
- Inside the glovebox, sometimes on a label.
- In the boot compartment, on a service sticker.
- In your maintenance booklet from the previous owner.
- On the radio unit itself, if it was removed before.
Can the Dealer Get You the Code?
A Audi dealer can usually retrieve the radio code using your A4 / S4 / RS4's VIN.
In most cases, you need to visit or contact them and show vehicle documents.
When it is verified, they can request the original anti-theft code for your radio.
Disadvantages:
- You usually need to visit in person and bring vehicle paperwork.
- Dealers often ask for payment for the lookup service and it can cost more than 100$.
- The process can take days depending on the model and database.
- Some older Audi A4 / S4 / RS4 radios may require manual lookup.
Searching for the Serial Number on your A4 / S4 / RS4
The only thing you'll need to get the code is your radio's serial num. (not part number!).
On all Audi's, you can find it in one of these places:
- Displayed on the radio screen (by using some combinations of buttons)
- On the radio body itself - you'll need to extract it and write down serial (which is not as hard as it seems).
Search for something like: Serial Num., SN, S/N, Serial, Serial Number...
1. View the Serial Number on Audi A4 / S4 / RS4's Screen
Audi A4 / S4 / RS4 radio does not show the serial number on the screen.
Unfortunately, the unit must then be extracted from the dashboard to find the serial on a factory sticker on the radio casing.
2. How to Find the Serial Number on the Radio Sticker
To find the serial number, you'll need to take out the radio unit out.
- Start by turning off the vehicle and removing the trim panel.
- Next, release the clips and slide the radio out to check the sticker on the back of the radio. Be careful not to damage the cables that the unit is connected to.
- Write down the serial number carefully and come back to our website.
- Know that serial number and part number are not equal. You will find both of them on the sticker, and you only need for the first one.
Example: Audi A4 / S4 / RS4 serial number label location
Common Serial Number Prefixes on Audi A4 / S4 / RS4 Radios
Your Audi A4 / S4 / RS4 radio serial number may start with:
AUZBP
Why Use Our Audi A4 / S4 / RS4 Radio Code Lookup Service?
Our Audi A4 / S4 / RS4 radio code lookup service retrieves the anti-theft code using the stereo serial.
Compared to dealership VIN lookup, this Audi A4 / S4 / RS4 radio code generator is more convenient, doesn't require vehicle documents, and costs less.
It's an easy way to restore access to your factory radio without leaving your home.
The Dealer's VIN Lookup vs FindRadioCode
- Delivery time: May take days, while FindRadioCode is almost instant 95% of the time.
- Availability: Dealers work business hours only, while our service is always available.
- In-person visit: Lookup can require a visit, while FindRadioCode works remotely.
- Pricing: It often costs over $100, while our service starts from 9.99 USD.
- Refund policy: Dealers usually offer limited refunds, while we include a full refund policy.
Now You Have the Code. How to Enter It?
You need to input the radio security code into the system to unlock your Audi's radio.
When the unit is locked, the screen usually shows a security message.
You should use radio presets, control knob, or touchscreen to enter the numbers, then confirm the code to reactivate the audio system.
Try not to make mistakes, because too many wrong attempts can disable your radio temporarily.
It will allow you a few missed shots before showing a LOCKED message.
You can try again by leaving the radio on for 60 minutes or a set waiting period.
A4 / S4 / RS4's Radio Code FAQs
Not all of them require a security code, but many factory radios use it as an anti-theft feature.
Newer and older models may not require a code depending on the head unit.
Free codes are uncommon.
You might find the code in the paperwork or from a dealer, but most require a serial number lookup.
Yes. Each stereo has its own unlock code. A used radio will need its original code to work.