Flashing SES- P0300 code - Details

I would like to clarify a few points regarding the stock ECM's tuning capabilities and the troubleshooting process for misfires.

First, it is important to understand that the stock ECM does not support individual cylinder tuning for either timing or fuel. We cannot adjust specific cylinders to balance fuel mixtures or spark.

Regarding misfires, GM truck logic does not provide codes for specific cylinders (e.g., P0301 or P0305). Instead, the system only triggers a general P0300 code. To identify a problematic cylinder, you must add "Current Misfire" channels (not history misfires) in HP Tuners and review the data. While small single digits at idle are normal for engines with aftermarket camshafts, a reading of 20–30 indicates a problem, and 50–100 suggests a dead cylinder.

Please be aware that individual cylinder misfires are mechanical issues, not tuning issues. If you have a flashing engine light or a confirmed misfire on a specific cylinder, it must be inspected mechanically. Most often, this is related to spark plugs and wires, particularly when using stock plugs in a modified engine or an incorrect plug gap.

As a reminder, we require log files to provide any advice or assess progress. Without these logs, we cannot determine if the vehicle is improving or worsening. Additionally, our policy states that after five emails or persistent mechanical issues that prevent us from completing the tune, a retune fee of $125.00 will apply.