Need help extracting line out signal from car radio

I'm trying to extract audio signal from my car stereo and use it as an input to my external amp. The place I want to get it from is marked in red in this picture: I used the IC31-34 pin12 to get the signal, but when I connected it to my external amp line in inputs it went to protective mode. I measured the voltage and it was 4V dc. Will it work if I put some resistors to lower the voltage?

My external amp has these pre-in parameters:

Pre-In sensitivity: 0.3 ÷ 5 V RMS
Pre-In impedance: 15 kΩ


Here is the full service manual of the stereo.

• Welcome to the site. Why did you pick pin 12? I don't think your amp wants DC. Oct 10 '18 at 17:04
• I think this EQ-FIX is modifying the signal so it sounds good on the factory low quality speakers. I followed the 4 channels outputs from IC22 controller and they all go to pin 12 of IC31-34. Oct 10 '18 at 17:21
• What is protective mode and which device went into that mode. Your question is unclear. Oct 10 '18 at 18:25
• You probably want at least a series capacitor for coupling the AC audio, and not the DC bias. However that may not be sufficient to do this safely. Oct 10 '18 at 18:40