P0758
Shift Solenoid B Electrical.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 7
- AreaTransmission
- 58
- FaultThe specific fault in that area
What it means
P0758 is the generic code for an electrical fault in the shift solenoid 'B' circuit of an automatic transmission. The transmission control unit commands the solenoid and monitors the circuit, and it set the code because the voltage or current did not match what it expected, which points to an open circuit, a short or a failed solenoid. Which gears solenoid B controls depends on the make, model and transmission.
Symptoms
- Gearbox stuck in one gear (limp mode), often third or a fixed higher gear
- Harsh, delayed or flared gear changes
- Missing gears or no upshift or downshift
- Gearbox warning light or malfunction indicator lamp on
- Poor acceleration or higher fuel consumption
- Transmission may not engage some gears after a restart
Possible causes
- Faulty shift solenoid B (open or shorted coil, or sticking internally)likely
- Damaged, chafed or corroded wiring between the solenoid and the transmission control unitlikely
- Poor connection at the transmission internal harness plug or connector (corrosion, bent pins, fluid ingress)likely
- Contaminated, low or degraded transmission fluid affecting the solenoid or valve bodypossible
- Low battery voltage or poor earth or power supply to the transmission control unitpossible
- Faulty transmission control unit (driver circuit failure)rare
- Valve body wear or debris causing the solenoid to stick or draw abnormal current (varies by transmission)rare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting any other transmission or battery voltage codes and the conditions when the fault set
- Check the transmission fluid level, condition and smell, following the manufacturer's procedure for that gearbox (some are sealed and need a specific temperature check)
- Check battery condition and charging voltage, and the power and earth supplies to the transmission control unit
- Inspect the wiring and connectors from the transmission to the control unit for chafing, heat damage, corrosion, water or fluid ingress and loose pins
- Measure the solenoid B resistance at the transmission connector and compare it with the specification for that model
- Check the wiring for continuity, short to earth and short to supply between the solenoid and the control unit
- Command the solenoid with a suitable scan tool where supported and watch for a response or a recurring fault
- If the wiring and solenoid test good, check for a software update or known fault for that transmission and consider testing the control unit
How to fix
- Replace the faulty shift solenoid B, or the solenoid pack, as the model requires
- Repair or replace damaged wiring and connectors, including the internal transmission harness if faulty
- Clean and reseat connectors and replace any corroded or damaged terminals
- Change the transmission fluid and filter if it is contaminated or degraded, using the specified fluid
- Repair charging, power or earth supply faults affecting the control unit
- Repair or replace the transmission control unit, or apply a manufacturer update only if a known fault is documented, once all other causes are ruled out
Can I keep driving?
Medium severity
The car can usually be driven carefully to a garage, but the gearbox may be in limp mode with limited gears. Continued driving risks further transmission wear and a breakdown, so get it checked soon.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.