The transmission pump is responsible for converting the rotational force generated by the engine into hydraulic pressure that activates the transmission and turns the drive wheels of your vehicle. If the hydraulic pump relay circuit does not operate according to the predefined parameters programmed in the ECU, a DTC P0946 will be recorded.
How severe is the code?
A diagnostic code P0946 means that the hydraulic pump relay/transmission pump relay may not be functioning correctly, which could impact the performance of the transmission pump itself. This could lead to a number of driving issues, as well as serious/expensive damage.
Symptoms
Symptoms of a P0946 include:
- Generally harsh gear shifts
- Slipping between gears
- The transmission will not shift gears
Causes
- Dirty fluid/filter
- Low transmission fluid level
- Damaged wiring and/or connectors
- Faulty hydraulic pump relay
- ECU or TCM issues
How to diagnose the code?
When diagnosing an OBDII fault code P0946, the hydraulic pump relay must be tested to ensure it is functioning. If it is, the transmission fluid level and condition should be checked. The wiring and connectors between the relay panel and the transmission panel should also be inspected for signs of damage and corrosion.
What repairs will fix P0946?
- Change the transmission fluid/filter
- Repair or replace damaged wiring and/or connectors
- Replace the hydraulic pump relay
- Reprogram or replace the ECU/TCM