P0457 on Jeep

The Jeep Grand Cherokee uses a Natural Vacuum Leak Detection (NVLD) approach for its EVAP system, implemented through the Evaporative System Integrity Module (ESIM) — commonly called the leak detection pump. The ESIM is a standalone unit (typically mounted on the charcoal canister near the rear driver-side wheel well) that seals the fresh-air vent and uses natural temperature-induced pressure changes to verify the fuel-vapor system holds vacuum. The internal seal/diaphragm and check mechanism in the ESIM are a well-documented common failure point on Chrysler/Jeep platforms. When the unit fails, the PCM cannot complete its EVAP self-test and falsely reports an EVAP leak, illuminating the check engine light even though no actual leak exists. Because the same codes are thrown by a loose or worn gas cap, the failure is frequently misdiagnosed: owners (and even shops) replace the gas cap first, the light returns, and the actual ESIM/leak-detection-pump fault is missed. A simple field test is to remove the ESIM and shake it — a rattle indicates the internal valve has come loose and the unit needs replacement. Note that the EVAP purge-valve hose on top of the engine also becomes brittle and cracks (covered by Jeep TSBs #25-002-15 REV-B and #18-035-20), producing the same codes, so the hose should be inspected before condemning the ESIM. This is an emissions-only fault: it does not harm the engine or transmission but will fail a state emissions/smog test.

The JK-generation Jeep Wrangler uses Chrysler's Natural Vacuum Leak Detection (NVLD) approach for its evaporative emissions (EVAP) system, implemented through a leak detection device commonly called the ESIM (Evaporative System Integrity Module) or leak detection pump (LDP). Rather than an active vacuum pump, this module monitors natural temperature-induced pressure/vacuum changes in the fuel/EVAP system to confirm the system is sealed. The ESIM is a known, high-frequency failure point: its internal diaphragm/seal hardens or cracks (or the housing cracks), causing the ECM to falsely detect an EVAP leak even when the system is actually sealed. The result is a check-engine light and one of several EVAP leak codes. Because the very first thing the code points the owner toward is the fuel cap, this failure is routinely misdiagnosed: owners (and shops) replace the gas cap one or more times, the light returns, and the actual culprit is the cheap ESIM/leak-detection module bolted to the charcoal canister. The module is a small white rectangular unit that twists/mounts onto the EVAP charcoal canister, located beneath the vehicle near the fuel tank / just ahead of the rear axle (driver side on most JKs). It is non-safety, non-drivability affecting, but it will cause a persistent CEL and an emissions/smog-test failure. This affects the 3.8L V6 (2007-2011) and 3.6L Pentastar (2012-2018) JK Wranglers, including 2-door and Unlimited 4-door.