P2A89

Code

Generic P — Powertrain

Alternative Fuel Pump C Compression Stroke Valve Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 27 RU: 16

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted wiring in the compression-stroke valve control circuit (short to ground).
Poor or corroded connector at the valve or wiring harness damage.
Failed compression-stroke valve/solenoid (high resistance or internally shorted).
Faulty fuel pump module or secondary pump driver/module.
Blown fuse or faulty relay supplying the valve or pump driver.
ECU/control module output driver fault or wrong software/calibration.

Symptoms

Illuminated Malfunction Indicator Lamp (MIL)/Check Engine Light.
Alternative fuel system may not switch to or maintain operation on alternative fuel.
Reduced or erratic alternative fuel pressure or delivery.
Engine roughness, hesitation, or stalling when running on alternative fuel.
Difficulty starting on alternative fuel or limp-home operation.

What to check

Read freeze-frame and live data with a scan tool; confirm MIL and related parameters (command vs actual state).
Check related fuses and relays for the alternative fuel pump/control circuits.
Visually inspect wiring and connectors to Pump C compression-stroke valve for damage, corrosion, or loose pins.
Backprobe valve connector and measure voltage and/or PWM while commanding the valve on/off from a scan tool.
Measure resistance of the valve coil with ignition off (compare to specification).
Check for short to ground between valve control circuit and chassis with multimeter.

Signal parameters

Control type: normally ECU/driver controlled (on/off or PWM) — verify in service manual for vehicle.
Expected command: 0–100% duty cycle if PWM; commanded state should change when requested by scan tool.
Typical voltages: inactive (open) near battery voltage; active/drive near 0–1 V if driver is low-side switching OR driven to ground depending on design — confirm vehicle-specific specs.
Typical coil resistance: manufacturer-specific; often in the tens to hundreds of ohms — check service data.
Typical PWM frequency: often tens to a few hundred Hz for solenoid valves — refer to OEM data.

Diagnostic algorithm

Retrieve codes and freeze-frame data. Note conditions (RPM, load, battery voltage, temperature) when the fault set.
Inspect visible wiring and connectors for Pump C compression-stroke valve. Repair any physical damage and reconnect securely.
Check fuses and relays that supply the pump/valve circuit; replace if blown or suspect.
With ignition ON (engine off), backprobe the valve connector and measure voltage while commanding the valve ON/OFF from a scan tool. Compare commanded state vs measured signal.
If the driver is PWM, observe duty cycle and frequency with a lab scope if available; confirm signal changes when commanded.
With ignition OFF, disconnect the valve and measure coil resistance across the valve pins. If resistance is open or shorted to ground, replace the valve.
Check for a short to ground between the control wire and chassis ground using an ohmmeter; repair wiring if shorted.
If wiring and valve are good but control signal remains low, check the pump module/driver ground and supply voltages. Verify the driver supply feed is present and within spec.
If wiring, valve, power, and grounds are good, suspect ECU/driver or fuel pump control module. Confirm with module bench tests or substitution per OEM procedures before replacement.
Clear codes and test drive to confirm repair. Monitor for recurrence and verify system operates normally on alternative fuel.

Likely causes

Connector corrosion or wiring short to ground at the valve harness (most common).
Failed compression-stroke solenoid on Pump C.
Failed or intermittent pump control module/driver.
Blown fuse or relay feeding the pump control circuitry.

Fault status

⚠️ Status

Control circuit for Alternative Fuel Pump C compression-stroke valve reports low voltage (below expected threshold). Possible causes include wiring short to ground, connector/corrosion, failed valve, blown fuse/relay, or driver/module fault. Further electrical checks required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours