P2670: Transmission actuator supply B is low or electrically open

P2670 is the transmission high-side actuator-supply-B circuit-low diagnosis in the reviewed GM table. The source explicitly says some controller hardware cannot distinguish a ground short from an open circuit, so the word low does not uniquely identify a shorted wire.

One code can cover two electrical signatures

The driver is checked while powered on. The table lists a short-to-ground design specification below 0.5 ohm to controller ground, or an open-circuit specification above 200 kilohms. These are controller detection specifications, not manual live-circuit resistance-test instructions.

That dual interpretation matters when choosing the next check. A circuit-low title alone is not enough to decide whether to search only for a ground contact; continuity and supply-path evidence may also be relevant under the applicable service procedure.

Driver availability is part of the test

High-side driver 2 must be on, the applicable diagnostic-enable calibration must permit the check, and service mode 04 must be inactive. Either failure path uses more than six failed counts within 2,400 samples at a 6.25-millisecond update rate.

A command issued while the supply driver is disabled does not reproduce the monitored condition. Preserve high-side status and any service-mode activity when interpreting a missing or intermittent result.

Verification should establish acceptable powered supply behavior and completion of the enabled diagnostic. The code does not identify which downstream actuator is defective or mandate a transmission-control-module replacement. The source lists Type A, one-trip behavior.

Source and applicability

These limits describe the stated monitor and require vehicle, hardware and calibration confirmation. GM diagnostic table, PDF page 1169.