Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC 78 - WASTEGATE Solenoid Fault: Notes
The PCM operates a solenoid to control boost. This solenoid is normally open. By providing a ground path the PCM energizes the solenoid which then allows vacuum to pass to the wastegate valve. During normal operation, the PCM compares it's wastegate duty cycle signal with the boost signal and makes corrections in the duty cycle accordingly. DTC 78 will set when:
- RPM greater than 1800.
- Fuel rate greater than 20 mm.
- Boost pressure greater than or less than desired (internal to PCM).
PCM will default to boost will shut down. Reduce maximum fuel.
- This step checks for a good vacuum source.
- This step checks for a faulty vacuum line or pump.
- This step checks the solenoid wiring.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.