P2A2C

Code

Generic P — Powertrain

Alternative Fuel Tank Shutoff Valve D Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 26 RU: 24

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Short to ground on the valve D control wire
Damaged or corroded connector at the valve or PCM
Open or high-resistance power supply or fuse for the valve circuit
Failed shutoff valve (stuck internally shorted or coil open)
Faulty PCM driver or internal electronics
Water ingress, contamination, rodent damage to wiring harness

Symptoms

Check Engine MIL illuminated
EVAP/alternative-fuel system warning or reduced functionality
Fuel system may not isolate properly (refueling or emission control issues)
Possible inability to start or run normally if system relies on valve state
Stored related DTC(s) and reduced drivability in some designs

What to check

Read freeze frame and freeze data, note conditions when code set
Verify vehicle battery voltage and main power (12V) is healthy
Visually inspect wiring and connectors at valve D and along harness for damage, corrosion, or water
Check fuses and relays related to the alternative fuel / EVAP systems
Backprobe valve connector and measure voltage with key ON and when commanding valve ON/OFF with a scan tool
Measure resistance of valve coil (with connector disconnected) against manufacturer spec

Signal parameters

Nominal coil resistance (typical range): 10–50 ohms (varies by vehicle) — compare to OEM spec
Key ON, valve not commanded: control pin often near battery voltage (~11–13V) or open-circuit; check OEM data
When PCM commands valve ON: control pin may be pulled low (0–0.5V) if PCM uses a low-side driver, or switched to ground/pulse-width modulated waveform — verify with scope
If circuit reads low (~0–1V) with valve not commanded, suspect short to ground
If circuit reads high or open with valve commanded, suspect open or power supply fault

Diagnostic algorithm

Clear codes and attempt to reproduce. Record conditions and monitor live data while exercising the valve if possible.
Verify battery voltage (≥12V) and inspect fuses/relays for the EVAP/alternative fuel system. Replace any blown fuses and retest.
Visually inspect connector at valve D for corrosion, bent pins, or water. Unplug and inspect female/male pin condition.
With ignition OFF, disconnect valve connector and measure coil resistance across valve pins. Compare to OEM spec. If out of range, replace valve.
With harness disconnected, check for continuity to PCM pin for the control circuit and for an unintended short to chassis ground (measure ohms to ground). Repair any damaged wiring.
With ignition ON (engine OFF), backprobe control wire at valve connector and measure voltage. Use a scan tool to command the valve ON and OFF while watching the voltage. Note if the line is low when it should be high or not responding.
If the voltage is low at the connector but good at the PCM pin, suspect harness short between PCM and valve; trace and repair.
If voltage is low at the PCM output pin, verify PCM ground and power supplies. If those check good and wiring is intact, consider PCM driver fault — confirm with manufacturer diagnostics before replacing PCM.
After repairs, erase codes and retest for at least one drive cycle to confirm repair. If intermittent, perform a wiggle test on harness while monitoring live data.

Likely causes

Chafed wiring contacting chassis ground (short to ground)
Loose/corroded connector pins at valve or harness
Blown or partially blown fuse/relay feeding valve circuit
Defective valve coil with abnormal resistance
PCM output driver degraded (after wiring checks)

Fault status

⚠️ Status

PCM detected low voltage on Alternative Fuel Tank Shutoff Valve D control circuit. Fault indicates control circuit reading near ground when higher voltage or commanded state was expected. DTC may be active or pending depending on conditions.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours