Before you declare your unit broken, check the manual. Here are three "failures" that are actually just feature settings.
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For fine-tuning, the DEH-P01 offers a dual 31-band graphic equalizer. This allows for independent adjustment of the left and right channels. The manual suggests using a Real-Time Analyzer (RTA) microphone to identify peaks and dips in the vehicle's frequency response. Because every car interior has unique reflective surfaces, the manual encourages users to use the EQ sparingly—cutting frequencies rather than boosting them—to maintain signal integrity and avoid distortion. Input and Media Compatibility pioneer dehp01 manual