P2401

P2401 means the ECM is seeing the EVAP Leak Detection Pump control circuit pulled low — voltage on the control pin is sitting near ground when it should be at battery voltage with the driver off, indicating a short to ground in the harness or a shorted solenoid winding. With the connector unplugged you should read battery voltage on the ECM-side control wire when KOEO and the pump commanded off (driver high-side disengaged); on the pump side, solenoid resistance should be 30-80 ohms across the two pins. Cheapest-first ladder: pull the connector at the pump and check whether the code transitions to P2400 (open) — if it does, the short is inside the pump or at the connector itself, not in the harness. Inspect the pigtail for melted insulation where the harness clips to the chassis (rear-axle pumps get rock-strike abrasion), measure the control pin to chassis ground with the connector unplugged (less than 100 ohms = harness short, infinite = harness OK), and current-clamp the supply circuit during a commanded activation (a shorted coil pulls more than 1.5A and trips the ECM's protection). Expensive misdiagnosis caveat: VW/Audi/Chrysler LDP is mounted in a notorious water-collection point above the rear axle — corrosion at the connector is the #1 root cause; replace the pigtail before replacing the pump, and check for a chafed harness where it crosses the rear subframe before assuming the pump itself shorted internally.

Vehicle-specific patterns: 1998-2009 VW/Audi (Jetta, Passat, Golf, A4, A6) frequently throws P2401 from a chafed-through harness where the EVAP loom crosses the rear axle beam — the insulation wears through and the control wire grounds against the chassis. 1998-2008 Chrysler/Jeep/Dodge (Sebring, Wrangler, Grand Cherokee) NVLD/LDP combination units short internally when water intrudes past the seal at the top of the unit, and the fix is the full assembly. 1996-2005 Mercedes-Benz (W202, W203, W211) throws P2401 from a failed pump solenoid that shorts winding-to-case after the canister assembly heat-cycles for a decade. Common LDP repair pattern: replace pump + harness pigtail together; standalone pump replacement leaves the same root cause. Estimated repair: $180 to $700.