Category: Powertrain → Turbo/Boost / Wastegate Control
What it means (plain English)
The ECM/PCM is seeing a higher-than-expected voltage or signal from the wastegate solenoid “A” circuit. In essence, the control circuit is reporting something is wrong (short, open, or voltage anomaly). It doesn’t always mean the wastegate is stuck closed—but that the controller sees an electrical fault in that solenoid’s circuit. RepairPal.com+3OBD-Codes.com+3YourMechanic+3
Symptoms you’ll notice
- MIL / Check Engine Light illuminated YourMechanic+2OBD-Codes.com+2
- Loss of boost / reduced engine power (boost may be limited) YourMechanic+2RepairPal.com+2
- Possibly erratic boost behavior, or turbo acting inconsistent YourMechanic+1
- In some cases, limp mode or protection strategies may kick in RepairPal.com+2OBD-Codes.com+2
Priority level
High (Electrical / Control). While it’s not necessarily catastrophic immediately, it can lead to mis-boost or overboost issues if the wastegate is uncontrolled. Best to diagnose promptly.
Common causes
- Faulty wastegate solenoid A (internally shorted or high resistance) OBD-Codes.com+2YourMechanic+2
- Wiring issues: open circuit, short to power, short to ground, damaged insulation RepairPal.com+3OBD-Codes.com+3Ecufiles+3
- Corroded or poor connector terminals at solenoid or harness YourMechanic+1
- Wastegate mechanical sticking or binding (if solenoid is attempting to actuate but mechanical side is jammed) YourMechanic+2OBD-Codes.com+2
- PCM/ECM internal fault (rare) OBD-Codes.com+1
How pros diagnose it (step-by-step)
- Scan & record freeze frame / PIDs
- Note when the code set, load/boost demand vs actual.
- Look for companion boost or sensor codes (MAP, VGT, underboost).
- Visual inspection
- Inspect wiring and connector for damage, abrasion, heat damage.
- Disconnect solenoid and check socket terminals; look for corrosion.
- Resistance / continuity checks
- Measure resistance across the solenoid; compare with spec (should not be open or shorted).
- Check continuity from solenoid to ECM (both power feed and control wire).
- Voltage checks
- With ignition on, confirm that the solenoid’s power supply line has proper voltage.
- Check control line: when commanded, does the ECM ground or drive the solenoid appropriately?
- Back-probe under operation / wiggle test
- Wiggle harness while monitoring solenoid signal; see if code trips or signal fluctuates (typical of intermittent wiring fault).
- Command solenoid via scan tool (if possible) and watch response.
- Solenoid swap / test
- If available, replace with known-good solenoid or swap with “B” if system has redundant solenoids (in some designs).
- Check mechanical side
- If solenoid and wiring check out, inspect the wastegate valve & actuator linkage to ensure it moves freely and isn’t stuck.
- Clear codes & retest under various boost/engine loads
Likely fixes
- Replace faulty wastegate solenoid “A”
- Repair or replace wiring / connectors (especially if shorted or broken)
- Clean / re-pin connector terminals
- Free or repair the wastegate mechanical valve / linkage
- In rare cases, repair/replace ECM if control driver circuit is bad
Related / companion codes
- P0243 — Wastegate Solenoid A Circuit (open/short) Kbb.com
- P0245 — Wastegate Solenoid A Low input YourMechanic+3YouTube+3OBD-Codes.com+3
- P0299 (underboost) Total Car Diagnostics+1
- P0234 (overboost)
- VGT / vane position codes (P2563, P003A)
Tech notes (quick hits)
- On many turbo systems, P0246 is purely an electrical control code (doesn’t necessarily mean pressure is off). OBD-Codes.com
- Some owners report that replacing just the solenoid without checking wiring often fails (the root cause was wiring/connector damage). Fiesta ST Forum+1
- Because the fault often involves control circuits, intermittent failures (wire breaks, insulation melts) are common—diagnostic steps involving wiggle testing are especially useful. Reddit+2Fiesta ST Forum+2