P2698: Downstream injection leakage can be inferred from temperature or oxygen

P2698 is the downstream-injection-system monitor in Ford’s diesel summary. The source describes two different evidence paths: a temperature-model comparison after a long soak and an oxygen-mass comparison for the specifically labeled P708 chassis-cab application. They should not be combined into one universal test.

The temperature strategy needs a long-soak opportunity

The first path is triggered after at least six hours of soak. It compares post-catalyst temperature with its modeled value under qualifying thermal, airflow, and engine conditions. Ford lists a 300-second session and thirty seconds with all entry conditions met.

The numeric failure difference is not published here. It would be unsupported to substitute a guessed temperature rise or treat any warm exhaust after start as leakage evidence.

The oxygen strategy has a narrower stated application

The P708 CC-only path runs during normal engine operation with valid NOx-sensor information and constrained airflow and modeled hydrocarbon conditions. It accumulates evidence from the difference between inlet and outlet integrated oxygen mass; a calibrated count and threshold determine failure.

Useful verification first identifies which strategy actually applies, then evaluates its own inputs and conditions. The summary does not locate a physical leak or prove a particular dosing valve failed. It supplies indirect monitor evidence and no universal leakage-test procedure. Further component testing requires the correct vehicle service information, especially before intervention in hot exhaust or fuel-delivery hardware.

Source and applicability

This explanation follows Ford’s 2023–2024 diesel OBD summary. Match the vehicle’s engine and calibration before applying these monitor values; a generic code alone does not establish fitment. Ford PDF, page 54 · Ford PDF, page 55.