2013 Enclave. What do DTCs P0700 and $07e8 indicate?

It's not that simple, the factory amp is monitored by, and fed data and signals from the Body Control Module. It is used for chimes and warnings and sounds like your indicator 'clicking'.

https://www.google.com/search?q=2012+buick+enclave+stereo+wiring

..

According to Wikipedia, 2009 to 2013 are the same transmissions

In its first year of production, the Enclave was often criticized for its 6-speed transmission, which was "hesitant to downshift."[7] For 2009, though, the powertrain is regarded as more competent with more abundant torque. For its entire production, it has been regarded as too heavy, weighing nearly 5,000 pounds (2,300 kg) with all-wheel-drive. Buick's VentiPorts have reappeared at the Enclave's introduction, a styling feature unique to Buick dating back to 1949.
Initial sales of the Enclave have been very strong, with demand far exceeding production capacity, forcing GM to add a third shift to the Delta Township plant.
With the arrival of the Buick Envision (which is slotted between the Enclave and Buick Encore) to North America in 2016 (for the 2017 model year), the Enclave will be bigger after Envision's debut, and the 2017 model year Enclave will be the last under the first generation platform.

ABS is likely on as well. Can be numerous causes. Typical cause when ABS and TCS indicators are on is a wheel speed sensor failure and there are 4. What did they do last time to fix the problem?

I recently experienced the same issue. The problem was the pressurized fuel pump. Apparently this is a know issue with the Enclave. When I took my 2013 Enclave to a Buick dealer they replaced pressurized fuel pump ($450 labor and parts) without charging me.

Did you preform recalibration after replacement ? See if this works ,if not you'll need to take it to the dealer an have it done with factory scan tool .
Alternate Method (w/o Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch to the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
6. Install the HVAC/ECAS fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

Buick Enclave No Start Problems - Car Forums at Edmunds.com

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100 ft lbs

DTC P2247: Front A/F Sensor (Bank 2, Sensor 1) VCENT Line High Voltage

NOTE:
Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
Information marked with an asterisk (*) applies to the front bank (Bank 2).
Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle for 2 minutes .
Check for Temporary DTCs or DTCs with the HDS.
Is DTC P2243 and/or P2247* indicated?

YES - Go to step 5.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM.

Turn the ignition switch OFF.
Jump the SCS line with the HDS.
Disconnect the A/F sensor (Sensor 1) 8P connector.
Disconnect ECM/PCM connector B (24P).




Connect A/F sensor (Sensor 1) 8P connector terminal No. 8 to body ground with a jumper wire.




Check for continuity between ECM/PCM connector terminal B13 (B21)* and body ground.
Is there continuity?

YES - Go to step 11.

NO - Repair open in the wire between the ECM/PCM (B13 (B21)*) and the A/F sensor (Sensor 1), then go to step 15.

Remove the jumper wire from the A/F sensor (Sensor 1) 8P connector, then reconnect ECM/PCM connector B (24P).
Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle for 2 minutes .




Measure voltage between ECM/PCM connector terminals B13 (B21)* and D10.
Is there about 0.2 V or less?

YES - Go to step 21.

NO - Go to step 14.

Replace the A/F sensor (Sensor 1).
Reconnect all connectors.
Turn the ignition switch ON (II).
Reset the ECM/PCM with the HDS.
Do the ECM/PCM idle learn procedure. See: Programming and Relearning
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?

YES - If DTC P2243 and/or P2247* is indicated, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to Step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - Go to step 20.

Monitor the OBD STATUS for DTC P2243 and/or P2247* in the DTCs MENU with the HDS.
Does the screen indicate PASSED?

YES - Troubleshooting is complete.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to step 1. If the screen indicates NOT COMPLETED, go to step 18 and recheck.

Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?

YES - If DTC P2243 and/or P2247* is indicated, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the ECM/PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM.

sounds like you got a bad bulb. turn the blinker on an step out to look at them. there should be a blown one.