802.11ac not working after update to 14.6.A.1.236 (5.1.1) C6833 Xperia Z Ultra

[bigstu_]

After updating to the latest ROM and resetting to defaults, I can see and connect to 802.11n (2.4GHz) networks but I cannot see 802.11ac (5GHz) networks any more. Wireless Network Scan does not see them at all so impossible to connect. No other issues with phone and have tried with multiple C6833 handsets. Anyone else experience this recently?

[Uliwooly]

@bigstu_

That's rather odd, could you test it in safe mode and also if possible, a different router?

[bigstu_ · Accepted solution]

Tried with multiple networks in multiple locations - doesn't matter how many - they are not being seen by the phone.

As mentioned, also tried with multiple handsets including NOS (new old stock) devices.

Only occurs with latest ROM.

I was able to trip over a solution - 5GHz networks became visible AFTER I installed a SIM.

I was scanning for networks without a SIM installed and could only detect 2.4GHz networks.

Once I installed a valid SIM and connected to a 3G network, scanning then revealed 5GHz networks.

Obviously there is no hardware reason that this should be the case - this phone has only one connection to the antenna module. Clearly this is a software issue and lack of proper quality assurance testing in the last release.

Fortunately persistance and ignoring logic paid off in this circumstance.