P268C: cylinder 1 injector adjustment data has not been programmed

P268C is an injector-data code for cylinder 1. In this GM monitor, “incompatible” specifically means that the end-of-line injector adjustment, or EIA, code has not been programmed. The row identifies diagnostic data identifier $60 for the cylinder-1 record.

Programming status is the failure criterion

The check runs with ignition on and calibration enablement. It reports a pass when the adjustment code has been successfully programmed, otherwise a failure. Type A, one-trip reporting is listed, with no elapsed-time specification. The source distinguishes production from development controller conditions; those gates are not service instructions to alter production-state counters.

What this means for diagnosis

This code does not measure cylinder contribution, injector leakage or injection current. Replacing an injector solely because P268C is present would skip the actual data-presence question. A useful review establishes which adjustment record the controller holds and whether an authorized programming process completed successfully.

The identifier is evidence of the monitored record, not a command sequence or permission to write an arbitrary value. Obtain the correct cylinder mapping and injector-specific adjustment information from the applicable service procedure. Verification is a successful cylinder-1 data check under its enabled conditions. A smooth-running engine or a cleared DTC does not independently establish that the required EIA record exists.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1509.