Citroën RD4 Radio Code

The Citroën RD4 and its successor the RD45 are the standard factory-fit radios for a wide range of Citroën models from the early 2000s through to the mid-2010s. Built by Philips/VDO (RD4) and Bosch/Clarion (RD45) under the PSA Group supply contract, both units are shared with Peugeot and use the same serial format — a C7 barcode sticker on the casing — and the same four-button code entry method. If your C3, C4, Berlingo or Picasso is showing CODE, here is the complete guide.

Why Does the Citroën Radio Lock?

Every RD4 and RD45 monitors its permanent 12-volt supply. A flat battery, a disconnected battery during a service, or even a brief electrical fault is enough to trigger the code-lock screen. This anti-theft feature was standard across PSA Group vehicles throughout the 2000s and early 2010s. The lock is released only by entering the correct four-digit PIN tied to the unit's serial number.

Finding the Serial Number on a Citroën RD4 or RD45

The serial is stored on the unit's C7 barcode label. You can read it two ways:

1. Preset button combination: Turn the ignition to position II (dashboard lit, engine off). Press and hold preset buttons 1 and 4 simultaneously for approximately three seconds. The display will show a diagnostic readout containing the serial number. On some C4 and Berlingo variants, holding all six preset buttons at once works instead. Write down the full string exactly as displayed.
2. Physical extraction: Use a set of DIN extraction keys (four flat metal hooks) to release the unit from the dashboard. The C7 barcode sticker on the top or side of the casing carries the serial. This is the definitive method if the button trick does not work.

Entering the Code

1. Ensure the display shows CODE (four dashes or zeroes).
2. Use preset buttons 1, 2, 3 and 4 to increment each digit to the correct value.
3. Press the confirm button — this is typically the fifth preset button or a dedicated OK/arrow key. The screen shows OK and the radio resumes.

Order your code using the serial at our Citroën brand page.

Citroën Models That Use the RD4 and RD45

Model	Generation	Years	Radio
C2	C2	2003–2009	RD3 / RD4
C3	C3 I / C3 I facelift	2002–2009	RD3 / RD4
C3	C3 II	2009–2016	RD4 / RD45
C4	C4 I	2004–2008	RD4 / RD45
C4	C4 I facelift	2008–2010	RD4 / RD45
C4	C4 II	2010–2018	RD5 / RT6 (higher trims)
Berlingo	Berlingo II (B9)	2008–2018	RD4 / RD45
C1	C1 I / C1 I facelift	2005–2014	RD3 / RD4 / RD43
DS3	DS3	2009–2015	RD4 / RD45

RD4 vs RD45 — What Changed?

The RD45 added Bluetooth audio streaming, a USB/AUX input on most variants, and MP3 playback from disc. The anti-theft lock mechanism, serial format, and code entry procedure are identical between both generations. You can identify which unit you have by looking at the fascia: the RD45 has a small Bluetooth status LED and usually a USB port on the front or side.

Troubleshooting

• WAIT after a wrong code: You must wait one hour with the ignition in ACC position before attempting entry again.
• Preset trick shows dashes instead of a serial: The unit may need 60 seconds of power before the diagnostic sequence populates. Try again after a short wait.
• Wrong serial format: Citroën RD4/RD45 serials are purely numeric or alphanumeric without a letter prefix such as AUZ or VWZ. If the string starts with a letter prefix you may be reading the part number rather than the serial — check for a separate line on the label.
• CODE reappears after correct entry: This can happen if the confirmation button was not held long enough. Re-enter the code and hold the confirm key for a full two seconds.

Frequently Asked Questions

Is the Citroën RD4 code the same as the Peugeot RD4 code for an identical-looking unit?

No — each unit is individually coded regardless of the badge on the car. Even two physically identical radios will have different serials and different codes.

My C4 Picasso shows an RT6 touchscreen — does that also need a code?

Some RT6 systems do require a code after a battery change. The entry method involves the touchscreen rather than physical preset buttons. For RT6 guidance, see our Citroën brand page.

The serial I retrieved via the button trick is only eight characters — is that correct?

Some early RD3/RD4 units produce an eight-character serial rather than a longer string. This is normal — enter the full eight characters when ordering.

Can a Citroën dealer provide the code for a car I bought second-hand?

Only if the vehicle's original sales records are accessible in their system. For second-hand cars with unknown history, serial-based ordering is more reliable.

What happens after multiple wrong attempts?

The RD4/RD45 enforces a timed lockout of approximately one hour per group of wrong attempts. The system does not permanently lock — it simply adds wait time after each batch of errors.