MODE 01 · PID 42
Control module voltage
This PID reports voltage observed by the responding control module. Adapter voltage and a meter reading at the battery are different measurement points.
- Formula
(256 × A + B) / 1000- Data bytes
- 2
- Units
- V
A worked decoding example
Request: 01 42
Response: 41 42 36 B0
Data: 36 B0 → 14 V
The example shows service, PID and data only. It omits adapter headers, CAN identifier, length and padding. It is not a live vehicle reading.
Reading context
Record key-on, cranking or running state. Smart charging systems vary their target; do not use one voltage threshold for every vehicle.
A decoded value is a measurement, not a diagnosis. Encoding limits are not normal operating limits. Confirm vehicle support and the manufacturer’s procedure.
Byte decoder
Formula(256 × A + B) / 1000 → V
A decoded value is a measurement, not a diagnosis. Encoding limits are not normal operating limits. Confirm vehicle support and the manufacturer’s procedure.
Sources
- python-OBD: Mode 01 command table ↗
- python-OBD: byte decoding implementation ↗
- CSS Electronics: OBD-II PID and response frames ↗
- California BAR: OBD test reference ↗
Independent reference; no affiliation with SAE, vehicle manufacturers or regulators. Sources checked 28 October 2026.