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Pixel 9 Pro - Mobile data not available during calls

Understanding the Dual SIM Behavior on the Pixel 9 Pro

We understand the frustration you are experiencing with your Google Pixel 9 Pro. The inability to access mobile data via your TIM Italia eSIM while actively on a call using your Vodafone Germany physical SIM is a perplexing issue, especially on a flagship device. While this might seem like a hardware defect or a carrier restriction, the root cause often lies in the specific architecture of Dual SIM, Dual Standby (DSDS) technology and the network bands currently in use.

When you utilize two SIM cards simultaneously on the Pixel 9 Pro, the device operates in a Dual SIM, Dual Standby (DSDS) configuration. This means the phone has only one primary radio transceiver that listens for incoming calls and data on both lines, but it can typically only maintain one active high-bandwidth data connection at a time. However, modern implementations like 5G and LTE usually support Data Switching or Data Downloading (DSDA), allowing data usage on the secondary SIM while a voice call is active on the primary SIM.

The specific issue you are facing—where the data connection drops entirely rather than switching—suggests a misconfiguration in the “Smart Dual SIM” or “Data Switching” settings, or potentially a restriction imposed by the specific combination of carriers you are using. It is important to clarify that the Pixel 9 Pro does support data usage during calls, provided the correct network settings and carrier configurations are applied. The drop to “connected but no internet” indicates the phone is failing to hand off the data session or is prioritizing the voice call on Vodafone to the exclusion of all other data streams.

We will explore the technical nuances of DSDS, the specific settings within the Pixel 9 Pro software, and the carrier-specific requirements that might be triggering this behavior. By systematically adjusting these settings, we can restore the functionality of simultaneous voice and data across different SIMs.

Network Architecture: DSDS vs. DSDA Technology

To solve this problem effectively, we must first understand the underlying technology governing your device. The Pixel 9 Pro, like most modern Android flagships, utilizes DSDS architecture.

Dual SIM Dual Standby (DSDS)

In a pure DSDS implementation, the device shares a single radio frequency chain between the two SIM cards. The phone camps on one network with one SIM while listening for paging signals on the other. If a call comes in on the idle SIM, the device switches the radio to accept that call. Crucially, in a strict DSDS mode, the data connection is often suspended on the active call SIM or cannot be initiated on the secondary SIM because the radio is fully occupied handling the voice call’s uplink and downlink.

Dual SIM Dual Active (DSDA) & Data Switching

The Pixel 9 Pro supports more advanced functionality. When you enable “Data Switching” or “Smart Connectivity,” the phone utilizes both LTE and 5G bands to maintain a data link even while a voice call (VoLTE) is active. This requires both the hardware (modem) and the software (Android telephony stack) to support this feature.

If your data connection drops completely, it implies the Pixel 9 Pro is falling back to a strict DSDS behavior. This usually happens for one of two reasons:

  1. One SIM is using 3G/2G for voice: If the Vodafone SIM drops to a 3G network for the call (due to lack of VoLTE coverage), the radio cannot handle simultaneous data on the TIM SIM.
  2. Smart Switching is Disabled: The software feature that manages the handover of data between SIMs is turned off.

Since you mentioned you are setting the network preference to 4G or 5G, and both carriers likely support VoLTE (Voice over LTE), the issue is almost certainly a configuration setting within the Pixel’s operating system.

Step-by-Step Troubleshooting for Pixel 9 Pro

We have compiled a comprehensive guide to configuring your Pixel 9 Pro for optimal Dual SIM performance. Please follow these steps in order.

Enabling Data Switching and Adaptive Connectivity

The most critical setting on the Pixel 9 Pro for this specific use case is “Data Switching.” This feature allows the phone to use the data SIM’s connection even when the other SIM is handling a voice call.

  1. Open the Settings app on your Pixel 9 Pro.
  2. Tap on Network & internet.
  3. Select SIMs (or “Mobile network”).
  4. Tap on your Vodafone SIM (the one used for calls).
  5. Look for the setting labeled “Allow this SIM to switch data” or “Data switching.” Ensure this is toggled ON.
  6. Go back and select your TIM eSIM.
  7. Ensure that “Mobile data” is toggled on for this SIM.
  8. Look for “Roaming” and ensure it is enabled (as you have done).

By enabling “Data switching” on the Vodafone SIM, you authorize the phone to temporarily pause data on Vodafone (if any) and prioritize data on the TIM eSIM while the call is active.

Verifying Preferred Network Type

If your network preference is set to a mode that restricts bandwidth, simultaneous voice and data may fail. We need to ensure the device is using LTE or 5G exclusively.

  1. Go to Settings > Network & internet > SIMs.
  2. Tap on Vodafone SIM (or the active SIM).
  3. Tap Preferred network type.
  4. Select 5G (recommended) or LTE/4G/3G (auto). Do not select “4G/3G/2G (auto)” if 2G is prevalent in your area, as 2G/3G networks often do not support simultaneous voice and data (SVDO).
  5. Repeat this for the TIM eSIM.

It is crucial that both SIMs are set to prefer 4G or 5G. If the Vodafone SIM falls back to 3G for the voice call (even if it shows “3G” or “H+” in the status bar), the radio hardware will be occupied, and the TIM eSIM data will cut out.

Managing Data Roaming Settings

Since you are using two international SIMs (Vodafone DE and TIM IT), roaming plays a significant role. The Pixel 9 Pro has distinct roaming settings for data and calling.

  1. Navigate to Settings > Network & internet > SIMs.
  2. Select TIM eSIM.
  3. Toggle Roaming to ON.
  4. Select Vodafone SIM.
  5. Toggle Roaming to ON (essential if you are in Germany and calling Vodafone, or if you are in Italy and Vodafone is roaming).

Sometimes, if the phone detects a “home” network for one SIM, it might aggressively restrict roaming data on the other SIM during a voice call to save battery or prioritize network registration. Ensure both are allowed to roam.

Carrier-Specific Considerations and VoLTE

A common hurdle with dual SIM setups, particularly with international carriers, is the compatibility of VoLTE profiles. The Pixel 9 Pro relies on Carrier Settings (provisioned via the SIM or Google Play Services) to enable advanced features like Data During Calls.

Vodafone Germany (D1 Network)

Vodafone Germany generally has excellent VoLTE support. However, if your Vodafone SIM is not provisioned correctly for VoLTE on the Pixel (since Pixels are not always officially sold in Germany, or might be imported), the phone might revert to 3G for voice calls.

TIM Italia (eSIM)

TIM Italia relies heavily on specific APN (Access Point Name) configurations for data to function correctly.

  1. Go to Settings > Network & internet > SIMs > TIM > Access Point Names.
  2. Ensure the selected APN is correct (usually internet or tim).
  3. If you have modified APN settings previously, ensure that the APN type includes default,supl and the APN protocol is IPv4/IPv6.
  4. Crucial Note: If the Vodafone SIM is handling the voice call on a 3G network, the TIM eSIM cannot access data. TIM does not provide the voice channel; it only provides data. The voice channel must be stable (VoLTE) on the Vodafone SIM for the data channel to remain open on the TIM SIM.

Wi-Fi Calling Interference

Wi-Fi Calling can sometimes interfere with Dual SIM Data switching. If Vodafone Wi-Fi Calling is active, the phone may prioritize the Wi-Fi connection for the voice call, potentially disabling mobile data on the secondary SIM to prevent routing loops.

Advanced Network Diagnostics

If the standard settings do not resolve the issue, we need to look at the specific network registration details of the Pixel 9 Pro.

Using Phone Information Menus

Android contains a hidden menu (*#*#4636#*#*) that provides detailed radio information. Note that this menu behavior can vary on the Pixel 9 Pro due to Google’s strict security implementations, but it is worth attempting.

  1. Open the Phone dialer.
  2. Dial *#*#4636#*#*.
  3. Select Phone information.
  4. Here, you can see the specific network type (e.g., LTE, NR), signal strength (RSRP), and whether VoLTE is provisioned.
  5. Check if “VoLTE provisioned” and “Wi-Fi calling provisioned” are checked.

If “VoLTE provisioned” is false for the Vodafone SIM, the Pixel 9 Pro will use CSFB (Circuit Switched Fallback) to 3G/2G for calls, which breaks data on the secondary SIM.

Testing Different Network Modes

To isolate the issue, we recommend forcing the Pixel 9 Pro into specific modes:

Note: Do not leave the SIM on 3G or 2G only, as this will guarantee the data failure you are experiencing.

Software Updates and Carrier Services

The Pixel 9 Pro relies on Carrier Services and Google Play Services to update the carrier configuration files (which define VoLTE and data capabilities). An outdated carrier configuration can cause the exact symptoms you are describing.

  1. Open the Google Play Store.
  2. Search for “Carrier Services” (by Google LLC). Update it if available.
  3. Search for “Google Play Services”. Update it.
  4. Check for System Updates (Settings > System > System update).

Google frequently pushes updates to fix Dual SIM behavior on Pixels. If you recently received a monthly security update, it is possible a bug was introduced. Check forums or the Magisk Modules repository for community-reported issues regarding the specific build number of your Pixel 9 Pro.

Hardware Limitations and Carrier Aggregation

While the Pixel 9 Pro is a powerful device, it is worth noting the physical limitations of the modem (likely the Snapdragon X80 or equivalent Exynos modem depending on region).

Modem Capabilities

The modem in the Pixel 9 Pro supports dual active SIMs (DSDA), but the efficiency depends on the carrier aggregation bands.

If you are in an area with poor Vodafone coverage, the phone may extend the listening period (drifting), reducing the timeslot available for TIM data.

Reset Network Settings

If all else fails, a “Reset Network Settings” on the Pixel 9 Pro can clear out corrupt APN configurations or stale connection states that are preventing the data handshake during a call.

  1. Go to Settings > System > Reset options.
  2. Select Reset Wi-Fi, mobile & Bluetooth.
  3. Warning: This will forget all saved Wi-Fi networks and Bluetooth pairings.
  4. After the reset, re-insert the eSIM details (or let them auto-provision) and reconfigure your mobile data preferences.

This often resolves deep-seated conflicts between the dual SIM stack and the modem firmware.

Conclusion: The Path to Resolution

The issue of mobile data dropping during a call on the Pixel 9 Pro is rarely a hardware defect. It is almost always a configuration or carrier provisioning issue. By ensuring that Data Switching is enabled, VoLTE is active on the voice SIM (Vodafone), and both SIMs are set to 4G/5G preferred, we can usually restore full functionality.

The Pixel 9 Pro is fully capable of handling data on the TIM eSIM while the Vodafone SIM is on a call, provided the network conditions allow for it. Focus on enabling the “Data Switching” feature in the network settings, as this is the specific toggle that controls the dual-data stream behavior. If the issue persists, the bottleneck is likely Vodafone’s VoLTE provisioning on the specific device IMEI, which may require a call to their support team to register the device fully for HD Voice services.

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