P2534: Transmission controller sees run/crank low while the ECM reports it active

P2534 is a low run/start circuit diagnosis in the reviewed GM transmission-control section. The controller compares its run/crank input with engine-controller run/crank status, so the code concerns inconsistent ignition-state information rather than simply a discharged battery.

The transmission-control comparison

The TCM row fails when its run/crank input is false while ECM run/crank status is true and the diagnostic is enabled. It uses 99 failing samples out of 240 at 25-millisecond intervals and lists Type A, one-trip behavior.

The comparison means that a low input with both controllers legitimately in an inactive state is not the same event. The useful evidence is the disagreement and its persistence, not a low value viewed without power-mode context.

The reporting module changes the details

A brake-controller row in the same file also assigns P2534 to a hardwired ignition circuit below 2 V while the engine-controller CAN status is high. That implementation uses 2.5 seconds and Type B, two-trip behavior. These are separate module strategies, not interchangeable thresholds for one test.

Identify which module stored the code before selecting a circuit diagram or reproducing the failure. Preserve the hardwired input and communicated ECM state together; a discrepancy does not, by itself, prove that the ignition switch is the failed part.

Verification should demonstrate agreement through the relevant power-mode transition and successful completion of the reporting module's monitor. The source does not establish a universal switch replacement or connector location.

Source and applicability

Confirm the reporting module, system and calibration before applying these diagnostic limits. GM diagnostic table, PDF page 1167. GM diagnostic table, PDF page 37.