P200E: close-coupled oxidation-catalyst overtemperature evidence

The broad P200E dictionary label is “Catalyst System Over Temperature.” GM's reviewed row narrows that to the downstream temperature of the close-coupled diesel oxidation catalyst, or ccDOC. The measured location matters when interpreting a scan record containing several exhaust-temperature channels.

Two exposure windows

A temperature above 800°C must produce 300 failing samples within 450 samples. A second, hotter branch uses above 900°C and 50 failures within 70 samples. Both operate on a 100-millisecond task. The hotter event therefore has a shorter qualification requirement than the lower-temperature event.

A single maximum-temperature number does not capture that distinction. Duration and the correct downstream ccDOC channel are necessary to understand which branch could have qualified. Do not substitute a downstream DPF value merely because both belong to the exhaust aftertreatment system.

Preconditions and interpretation

The diagnostic must be enabled, the engine running, battery voltage acceptable and the downstream ccDOC temperature sensor free of the relevant fault. These are prerequisites to a valid overtemperature judgment. A faulty temperature channel can inhibit the check rather than demonstrate cooling.

The source lists Type A, one-trip reporting. Verification should establish credible temperature data and monitor execution; the code alone does not determine catalyst damage or the reason for the heat event. Heat-related inspection and service testing require an appropriate professional procedure. This article covers the documented 2025 GM monitor only, not every vehicle that uses the generic P200E label.

Source: GM monitor, PDF page 1384.