P219E: cylinder-three imbalance requires trustworthy timing information

P219E is the cylinder-three member of the documented air-fuel imbalance group. GM's table describes a comparison between a cylinder's calculated air-fuel behavior and the average for its bank. It is an imbalance finding, not an instruction to replace the third injector listed on a parts diagram.

Check the validity of the underlying comparison

The source requires engine-roughness information to be valid. Trigger-wheel adaptation for individual-cylinder segment-time correction must be complete, segment durations must be plausible, and the engine must be synchronized in normal operation. An investigation should therefore preserve relevant timing and adaptation status along with the mixture-related data.

This does not mean that P219E proves a trigger-wheel defect. Those conditions are prerequisites for the imbalance test. Confusing an enabling condition with the fault being diagnosed can send the repair in the wrong direction.

Keep rich and lean evidence separate

The same P219E code is listed under both too-lean and too-rich branches. The normalized thresholds are on opposite sides of the bank comparison, so the actual direction must be established from diagnostic evidence. A generic scanner title does not supply that direction.

The operating region is also restricted by speed and air charge, and the comparison is listed once per driving cycle. A brief idle check may not provide a new valid result. Use the exact engine's diagnostic information to investigate cylinder three and any related faults. Successful verification means a credible, completed comparison under the required conditions, rather than only an empty fault-memory screen.

Source and applicability

GM 2020 20OBDG07 shared cylinder air-fuel imbalance monitor. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.

20OBDG07 Diagnostics, physical PDF pages 129, 130, 131, 132, 133, 134.