P0935
Hydraulic Pump Relay Circuit/Open
Open circuit at the auxiliary hydraulic pump relay used to maintain transmission line pressure during start-stop or hybrid operation.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Relay coil openCommon
- Wiring breakPossible
- Pin pushed back out of connector bodyLess likely
Parts involved
- Hydraulic Pump Relay
- Auxiliary Hydraulic Pump
- Wiring Harness
P0935 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.