Onkyo receivers don't use a big numbered fault system — they show short messages or signal a problem with a blinking light. Here's what the common ones mean and how to fix each, grouped by where the trouble actually is.
Speaker setup: "NG" messages
During automatic setup (AccuEQ), an "NG" result for a channel (e.g. "NG: L R") means the receiver couldn't detect that speaker through the calibration mic. Causes: a loose/reversed/shorting speaker wire, the mic not fully plugged in or poorly placed, a noisy room, or a silent speaker. Fix: re-seat the speaker wires (+/− correct, no stray strands), plug the SETUP MIC fully in at ear height pointing up, run it in a quiet room, and confirm the speaker actually plays. (Full walkthrough: Onkyo NG: L R speaker fix.)
The receiver blinks / drops into standby
A receiver that blinks and shuts off, or won't power up, is in protection mode — it sensed a fault on the amp output. Cause: almost always a speaker-wire short (a stray strand bridging the terminals), sometimes overheating or an internal fault. Fix: unplug, check every speaker terminal for shorts; test with all speakers disconnected (if it stays on, reconnect one at a time to find the bad cable); give it ventilation if it only trips when hot; power-cycle (unplug at least 30 seconds) and reset if it trips bare.
HDMI / "No Signal" / no picture
No picture or "No Signal" through the Onkyo means an HDMI handshake or passthrough problem. Fix: confirm the input assignment, reseat the cable, set the TV/source power-on order (source → receiver → TV), swap in a certified cable, and update the receiver's firmware. If the receiver passes audio but no video (or vice-versa), it's usually an HDMI board/handshake issue — test the source straight to the TV to isolate it.
No sound (everything connected)
If there's a picture but no audio, check the listening mode (not on a silent/Pure-Direct mode that disables processing), the input's audio assignment, and that the speakers are configured. For ARC from the TV, enable HDMI Control (CEC) and set the TV's audio output to the receiver.
Network / streaming errors
Network messages mean the receiver can't reach the internet or a service. Fix: reboot the router and receiver, re-run network setup, set a public DNS at the router (8.8.8.8), and update firmware. Wired Ethernet is more reliable than Wi-Fi for AV receivers.
FAQ
What does NG mean on my Onkyo? A speaker calibration failure — the receiver couldn't detect that channel through the mic. Usually wiring or mic placement, not a fault.
My Onkyo blinks and turns off. Protection mode, from a speaker-wire short most often. Disconnect all speakers and power on; if it stays on, reconnect one at a time to find the short.
No picture through the receiver. An HDMI handshake issue. Check the input assignment, reseat/swap the cable, power on source → receiver → TV, and update firmware.
It passes video but no sound. Check the listening mode and input audio assignment; for TV audio over ARC, enable HDMI Control and set the TV output to the receiver.