P2438: Bank 2 AIR pressure high voltage and the 94% boundary

P2438 identifies the high electrical boundary of the Bank 2 secondary-air pressure signal in this GM monitor. The criterion is a sensor signal above 94% of the 5 V reference. It does not say that actual AIR pressure exceeded 94% of a mechanical system limit.

Avoid interpreting an invalid input as real pressure

A high displayed pressure can accompany a high signal voltage, but the code itself questions the electrical input. Deciding that the exhaust path must be restricted from that displayed value alone would assume the very measurement the controller has rejected.

GM separates this check from P2436, which compares pressure with barometric pressure, and P2435, which looks for a signal stuck in range. A signal at an electrical extreme, a believable but biased signal and a flat signal during pump operation require different evidence.

What the sample history contributes

The fault requires 800 failing samples within 1,000 samples on a 6.25-millisecond loop. It uses a two-trip Type B illumination strategy. A momentary high reading is therefore not a complete description of the decision, and a later normal reading does not erase the earlier sample history.

Controller processor and 5 V reference faults are listed as disabling conditions. Review that supporting information before attributing a high signal to the sensor itself. A meaningful verification confirms that the electrical-range monitor has passed under the applicable vehicle conditions; merely hearing the AIR pump operate does not test the upper signal boundary.

Source and applicability

GM 2009 09OBDG11 Engine Diagnostics, Dual Bank section, only the cited secondary-air monitor. Physical bank location and per-code vehicle applicability require vehicle-specific service information.

General Motors source, physical page 146 · General Motors source, physical page 147 · General Motors source, physical page 148