Code
P1400
SUBARU
P — Powertrain
Fuel Tank Pressure Control Solenoid Low Input
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in FTPC solenoid circuit
- Corroded or loose connector at the solenoid
- Failed/shorted FTPC solenoid (coil/electronics)
- Faulty ground or power supply to solenoid
- ECM input driver fault (rare)
- Aftermarket modifications or recent fuel tank/EVAP service damage
Symptoms
- Malfunction Indicator Lamp (MIL/CEL) illuminated
- Failed emissions test or readiness monitor not set
- Possible fuel smell near tank or EVAP components (occasionally)
- Reduced ability to control fuel tank pressure resulting in EVAP fault codes
- No noticeable change in driveability in many cases
What to check
- Retrieve freeze frame and related EVAP/FTPC PIDs with a scan tool
- Visually inspect wiring and connector at the FTPC solenoid and fuel tank area
- Back-probe the solenoid connector and check for supply voltage and ground when key ON and when commanded
- Measure solenoid coil resistance and compare to factory specification
- Command the solenoid ON/OFF with a scan tool and listen/feel for click or observe electrical change
- Check for continuity to ECM and for shorts to ground or battery
Signal parameters
- Expected coil resistance: typically low ohms (example 10–50 Ω) — consult factory spec for exact value
- Supply voltage: battery/ignition voltage present at supply pin (with key ON)
- Control signal: ECM grounds or modulates the control pin (0 V when commanded to activate or PWM present) — confirm with scanner/oscilloscope
- When commanded ON, current should flow through the coil and a click or change in circuit current may be observed
- No voltage or a persistently low voltage on the control/input circuit indicates open/short or poor supply
Diagnostic algorithm
- Connect a professional scan tool, read freeze frame, pending codes, and live data for FTPC/PIDs.
- Visually inspect the FTPC solenoid, harness, and connector at the fuel tank for damage, corrosion, or looseness.
- With key ON (engine off), back-probe the solenoid connector: verify battery/ignition supply and the control/ground reference. Record voltages.
- Command the FTPC solenoid ON/OFF with the scan tool and observe whether the control circuit switches (voltage/ground or PWM). Listen for a click.
- Remove the connector and measure coil resistance. Compare to factory specification. An open or shorted coil indicates a failed solenoid.
- If resistance and voltages look incorrect, perform continuity checks between the solenoid connector and ECM pins to locate open circuits or shorts to ground/power.
- Repair any damaged wiring/connector; replace the FTPC solenoid if out of spec. Clear codes and perform a drive cycle or readiness test.
- If wiring and solenoid test good but the circuit still fails, consider ECM input/driver fault and follow manufacturer procedures for ECM testing or replacement.
Likely causes
- Damaged wire insulation with short to ground
- Connector pin corrosion at solenoid harness
- Failed FTPC solenoid internal coil or electronics
- Blown fuse or poor battery/ignition supply to EVAP circuits
- PCM/ECM driver defect (less common)
Fault status
Status
FTPC solenoid circuit low input detected — possible open/short, poor supply/ground, or faulty solenoid. Inspect wiring/connector and test solenoid per factory procedure.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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