P2670: Actuator Supply Voltage B Circuit Low
What to do
Expect several warning lights and reduced power, probably coming and going rather than being constant.
As at P2669, do not let a list of unrelated parts be replaced on the strength of these codes. A shared power supply has failed and everything on it reports itself faulty.
Mention exactly when it happens — under load, going up a hill, with the air conditioning on, in a particular gear. A supply that fails only when several parts draw current at once points at a weak connection rather than a dead short, and that is a different and much cheaper repair. Ask for voltage-drop testing while the circuit is working, not just a continuity check, because a bad joint measures perfectly when nothing is flowing through it.
If the supply itself tests sound, the remaining possibility is one faulty part dragging the shared supply down — and that is found by disconnecting them one at a time, not by replacing them all.
What this code means
The second actuator supply rail reads below its valid range — a short to ground, or a supply that has collapsed under load.
What a supply rail is, and why its failure produces a list of codes naming unrelated healthy parts, is explained at P2669.
The distinction that matters on this code is between a rail that is shorted and a rail that is merely sagging, because they lead to different repairs. A dead short pulls the rail down whenever it is switched on, and the module usually shuts it off protectively — everything on the rail stops together and stays stopped. A rail sagging under load behaves quite differently: it holds up at idle with few actuators working and drops when several draw current at once, so the faults appear under load, in a particular gear, or only with the air conditioning on. That intermittency reads as several flaky components rather than one weak supply.
A sagging rail is nearly always resistance in the supply path rather than a short at all — a relay whose contacts have degraded, a corroded ground, a connector pin that has lost tension. The test is voltage drop while the rail is loaded, not a static reading, because a resistive joint measures perfectly at rest.
One actuator can also pull the rail down on its own: a solenoid whose winding has shorted internally draws far more than its share and starves everything beside it. That is the one case where a component named by another code genuinely is the culprit — so if the supply path measures sound under load, the next step is disconnecting the rail's actuators one at a time.
Likely causes
Start here
- Wiring shorted to ground · moderate
- High resistance in the module supply · moderate
- Poor module ground connection · moderate
- Faulty module power relay · moderate
Less common
- Shorted injector dragging the driver down · moderate
- Damaged module supply wiring · moderate
Symptoms
Components involved
Information, not instruction
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Community experience
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