Diagnostic Aids

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.

If there is an open fuse that supplies an input voltage to the BCM the DTC P2534 may set.
If an open fuse that supplies voltage to the BCM is found it is likely to be caused by a short to ground on an output circuits from the BCM and is not likely to be the module itself. Do not replace the module before isolating all output circuits first.
A short to B+ or an open in the KR73 Ignition Main Relay coil control circuit can cause a DTC P2535 to set.
A open or high resistance in the KR73 Ignition Main Relay coil ground circuit can cause a DTC P2534 to set.
Stuck or open contacts in the KR73 Ignition Main Relay can cause a DTC P2534 to set.
If the vehicle has Data Communication Related DTC's, diagnose those DTC's First.
The DTC P2535 sets if there is voltage present on the Run/Crank Ignition 1 Voltage circuit when the KR73 Ignition Main Relay is not commanded on by the K9 Body Control Module, or P2534 will set if No voltage is detected on the Run/Crank Ignition 1 Voltage circuit when the KR73 Ignition Main Relay is commanded on by the K9 Body Control Module.
A short to voltage in the ignition circuit will keep the vehicle modules awake, which can drain the vehicle's battery.

NOTE:

The circuit numbers listed below are a general overview and may not reflect the Wiring Schematics for this document.

The last 2 digits of the circuit number are significant in identifying its power and/or ground function.
- Circuits ending in 42 are primary fused B+ circuits (generally the first fuse in the circuit after the battery)
- Circuits ending in 40 are secondary fused circuits (generally fuses in a fuse block after the primary circuit)
- Circuits ending in 39 and 41 are ignition voltage circuits.
- Circuits ending in 50 are grounds.
- Circuits ending in 51 are low reference (ground).