OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P0935?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyRelay coil open
- PossibleWiring break
- Less likelyPin pushed back out of connector body
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
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Hydraulic Pump Relay, Auxiliary Hydraulic Pump, Wiring Harness
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.