P2742: Cooler-out temperature circuit low is a voltage-window fault

P2742 maps the generic transmission-temperature-B circuit-low description to the cooler temperature input in this source. Its narrative checks input voltage below the working window, with a listed threshold of 200 mV and 30 mV hysteresis. The measurement column is labelled “resistance,” however, despite the voltage units; that inconsistency remains flagged.

Do not convert circuit low into cold fluid

The supported interpretation is an electrical input outside the expected range. It does not establish the actual fluid temperature. Confirmation requires at least 500 ms, rather than treating every brief threshold crossing as a completed fault.

The controller requires battery voltage above 8.75 V and below 18 V, with no cranking or stop-key state. P0882 and P0883 disable this monitor, making power-supply context relevant to a repeat check.

Evidence for follow-up

Retain raw input data, fault status and controller supply information. A converted temperature reading alone may conceal the out-of-range electrical condition. Because the source’s measurement label is inconsistent, do not reinterpret the printed millivolts as an ohmic test specification. Use vehicle-specific service documentation to resolve the circuit and test method before drawing a component-level conclusion.

Document scope and source

2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.

GM physical PDF page 908.