Blackwing: ESE Disable

When the CT5 platform was announced in 2019 there were two audio systems. Both implemented Engine Sound Enhancement (ESE), "to accentuate natural powertrain and exhaust system sounds and deliver them to the cabin at the right levels during the correct times." ESE is implemented using three microphones in the headliner and Active Noise Cancellation (ANC) circuitry in the audio amplifier.

Many people (including me) do not like "fake engine noise." Currently the only way to disable it is to disable ANC itself. There is a report that disconnecting one of the headliner microphones is enough to completely disable ANC. Another approach is an "ANC bypass harness", basically a short M/F cable that is installed between the amplifier and a vehicle harness. Several companies make these. I got mine from LLJ Custom Car Audio Fabrication. The 2022 and up RPO UQS application is GMBB4. Both PAC Audio and Metra also make these, but so far not for the CT5. Trifecta Performance, Inc. claims to be able to disable ANC and/or ESE via their "calibration products" but the details are murky and they do not currently work for the CT5.


ANC Bypass Harness	UQS Amplifier

Here's the pinout for the CT5 audio amplifier X3 connector (with RPO UQS):

Pin Wire Color Description

1 YE Automotive Audio Bus A2B Serial Data 1 [-]

2 WH Automotive Audio Bus A2B Serial Data 1 [+]

3 — (not used)

4 — (not used)

5 — (not used)

6 GY/BU active noise cancellation microphone 3 signal

7 BU/YE active noise cancellation microphone 2 signal

8 GN/BN active noise cancellation microphone 1 signal

9 — (not used)

10 — (not used)

11 BU/WH AUTOSAR Can Bus [+] 5 Serial Data

12 BU/YE AUTOSAR Can Bus [-] 5 Serial Data

13 — (not used)

14 GY/BK active noise cancellation microphone 1 feedback signal

15 BU/BK active noise cancellation microphone 2 feedback signal

16 GY/BN active noise cancellation microphone 3 feedback signal

Only the bold pins are present in the LLJ harness. Essentially the six pins from the three microphones are left out.

Some have reported the bypass harness disables the tweeters. I tested my Blackwing with and without the bypass harness and in both cases a 10 kHz test signal (via the iphone " tone generator speaker cleaner" app) sounds different when I cover the driver's A pillar tweeter with my hand.

I suspect this is an issue for some or all CT4 Cadillacs and some early production CT5 Cadillacs. For example the T3 amplifier X3 connector pinout for a 2022 CT5 has the same six circuits used by the three headliner microphones but instead of canbus in/out circuits there are eight circuits for front/rear midrange/tweater speaker signal/control.

If you have a CT4 or early CT5 and want to know if a bypass cable will work with your car, look at the wires on the car harness side of the X3 connector. If you only see the four canbus and six microphone circuits (see below) then a bypass cable will likely work as expected.


T3 Amp X3 (pins 1-8)	T3 Amp X3 (pins 9-16)