Fault codes covered
26-27
Code 26-27 indicates that an attempt for the PCM to reprogram itself failed. If this diagnostic is not recent, then a subsequent reprogramming attempt may have succeeded. The technician should check the current PCM software version against the latest software release. If the PCM software is not the most current, then the PCM should be reprogrammed manually using the Infinity System Control or the Carrier Service Tech App for 26VNA/27VNA/ models, or using the USB port for 27VPA models.
Source: ACHPVSR454-02SM troubleshooting pages.