Indoor unit displays E6 and does not cool or heat; outdoor unit may not start

Safety first: Turn off power at both indoor and outdoor disconnects. Communication wiring carries low voltage but is adjacent to high voltage terminals.

Steps to try:

• Check wiring connections: Remove the front cover of the indoor unit and the service panel of the outdoor unit. Verify that the communication terminals (often labeled S1, S2, S3 or 1, 2, 3) are wired identically at both ends and that screws are tight.
• Inspect cable: Follow the communication cable along its route. Look for cuts, rodent damage, or splices. Replace damaged cable with appropriately rated 14–18 AWG stranded cable as specified by Pioneer.
• Polarity check: Ensure that the same numbered terminal at the indoor unit goes to the same numbered terminal at the outdoor unit. Reversed wires can cause E6.
• Power reset: After correcting any wiring issues, turn power back on and wait 5–10 minutes for the units to re-establish communication.

When to call a pro: If wiring is correct and E6 persists, either the indoor or outdoor main PCB communication circuit may be defective.