Code
P0443
HUMMER
P — Powertrain
EVAP Purge Solenoid Valve 1 Control Circuit
AI status
Completed
Completed
100%
Causes
- Open or short in purge solenoid wiring or connector
- Corroded, loose, or damaged electrical connector at the purge valve
- Failed EVAP purge solenoid (stuck or coil open/shorted)
- Blown fuse or poor power supply to the purge solenoid circuit
- Poor or missing ground for the circuit
- PCM/ECM driver fault (rare)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated (check engine light)
- Failed emissions or EVAP-related readiness test
- Possible fuel odor from engine bay or fuel tank area
- Reduced EVAP system performance (purge not operating properly)
- Rarely, rough idle or drivability issues if severe
What to check
- Scan PCM for DTC(s) and freeze frame / live data for purge valve command and status
- Visually inspect purge valve connector and wiring for damage, corrosion, or water
- Check relevant fuses and power distribution for EVAP circuit
- Back-probe purge valve connector and measure voltage and ground while commanding ON/OFF
- Measure coil resistance of purge solenoid with multimeter
- Perform wiggle test on harness while monitoring live data/DTC
Signal parameters
- Battery supply to purge solenoid: approx. 12 V (key ON) at the supply terminal — verify with vehicle spec
- Coil resistance (typical): ~20–40 ohms (varies by model) — consult factory data for exact value
- PCM control: usually a switched ground driver or PWM ground; when commanded ON expect near 0–1 V at control pin (to chassis) and a pulse pattern when modulated
- When OFF: control pin typically near battery voltage or open circuit; no continuous short to ground (5 kΩ) in control path
- PWM frequency if used: commonly in the range of 10–200 Hz (model-dependent)
Diagnostic algorithm
- Retrieve and record all EVAP-related DTCs and freeze-frame data with a scan tool. Confirm P0443 is current and note conditions when stored.
- Perform a thorough visual inspection of the purge solenoid, connector, and wiring harness for damage, corrosion, or disconnection. Repair obvious faults.
- Verify power and ground: with key ON, check for battery voltage at the purge solenoid power terminal and a good chassis ground.
- Back-probe the control wire and monitor with a scan tool while commanding the purge valve ON/OFF. Observe voltage behavior and compare to expected signal parameters.
- Measure coil resistance at the solenoid. If resistance is out of expected range or infinite/short, replace the solenoid.
- If coil resistance is good but no command is reaching the solenoid, check continuity between the solenoid control pin and the PCM control pin. Repair opens/shorts as needed.
- If intermittent, perform wiggle test on harness and connector while monitoring live data/DTC. Repair broken wires or poor connectors.
- If wiring and solenoid check good, verify PCM driver operation: check for correct command signal from PCM with known-good load or scope. Replace PCM only after confirming internal driver failure per factory procedure.
- After repairs, clear codes and perform readiness/EVAP leak tests to confirm the fault does not return.
Likely causes
- Damaged connector or wiring harness to purge solenoid (most common)
- Faulty purge solenoid (coil open or internally shorted)
- Loose or corroded ground/power connection
- Blown fuse or fusible link in EVAP power feed
- PCM output driver failure (least common)
Fault status
Status
MIL ON — P0443: EVAP Purge Solenoid Valve 1 Control Circuit malfunction detected by PCM. Electrical fault (open/short/intermittent) in purge valve control circuit.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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