P28C3

Code

Generic P — Powertrain

EVAP System High Load Purge Line B Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 61 RU: 34

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Page language: EN

Causes

Restricted, collapsed or disconnected purge hose/line B
Clogged or saturated charcoal canister or purge circuit
Faulty purge solenoid/valve B (stuck open, stuck closed, internal leak)
Leaking or faulty vent/vent control valve affecting pressure differential
Faulty EVAP pressure/vacuum sensor or manifold pressure/MAF sensor errors
Wiring harness/connectors open, shorted, corroded or poor ground in purge circuit

Symptoms

Check Engine Light (MIL) illuminated, code P28C3 stored
Poor acceleration or hesitation under load if purge flow is excessive
Fuel odor near vehicle if EVAP is venting
Failed emissions test or elevated evaporative emissions
Possible rough idle or drivability issues when purge duty changes

What to check

Read freeze frame and live data (purge command, purge duty, EVAP pressure/vacuum, MAF/MAP, fuel trims)
Visual inspection of purge line B, hoses, clamps and canister for damage or disconnection
Operate/command purge valve B with scan tool and verify response
Measure purge valve B resistance, voltage and ground with multimeter
Perform smoke test to locate leaks or restrictions in EVAP lines and connections
Inspect vent valve and canister for clogging or saturation

Signal parameters

Purge valve B commanded duty cycle (%)
Purge valve B commanded ON/OFF state
Purge valve B supply voltage and ground integrity (V)
Purge valve coil resistance (Ω)
Intake manifold vacuum/pressure (kPa or inHg)
MAF (g/s) or MAP (kPa) and engine load/RPM

Diagnostic algorithm

Retrieve code, freeze frame data and additional EVAP-related codes. Confirm conditions when code set (engine load, temp, RPM).
Perform a thorough visual inspection of purge line B, connectors, vacuum hoses and charcoal canister. Repair any obvious damage.
With engine off, remove and inspect purge valve B for contamination or sticking. Check valve resistance and compare to spec.
Use a scan tool to command purge valve B while monitoring intake vacuum/pressure and purge duty. Confirm valve actuates and the expected pressure/flow changes occur.
Perform a smoke/leak test on the entire EVAP system including purge line B and vent path. Repair any leaks or restrictions found.
Verify upstream sensors (MAF, MAP, EVAP pressure sensor) are reading correctly during commanded purge events. Check fuel trims for abnormal responses.
Check wiring and connectors for voltage supply, ground and signal continuity at purge valve B. Repair wiring faults as needed.
If valve and plumbing check good but fault persists, inspect vent/vent control valve and charcoal canister for internal restrictions or saturation; replace components as required.
After repairs, clear codes, perform a drive cycle including high-load conditions or use diagnostic tool to replicate conditions and confirm code does not return.

Likely causes

Collapsed or kinked purge hose B causing restricted flow under load
Purge solenoid B not modulating correctly (electrical or mechanical failure)
Large leak elsewhere in EVAP (vent circuit) altering expected pressure response
Clogged purge port or charcoal canister limiting flow
Intermittent wiring fault or connector corrosion to purge valve B

Fault status

⚠️ Status

EVAP purge circuit B performance abnormal under high-load conditions — PCM detected incorrect purge flow/pressure when purge was commanded. Inspect purge valve B, lines, canister, vent and related sensors/wiring.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours