How the 4XE Works

Three Electrical Systems Running Simultaneously

The 4XE manages three distinct electrical systems at the same time. Understanding the architecture explains why software quality matters so much on this platform — and why a software fault can affect the whole vehicle, not just one system.

The hybrid control module manages power flow between all three systems, plus the 2.0L turbocharged gasoline engine. A software fault in that module can affect all three systems simultaneously — which is why the OTA software update recall (affecting ~24,000 vehicles) caused sudden loss of propulsion rather than a partial failure.

The Two Electric Motors

Front Motor

Integrated into the 8-speed automatic transmission, replacing the traditional torque converter. Provides front-axle electric torque and enables regenerative braking. Works in combination with the gasoline engine in hybrid mode, or independently in full EV mode.

Rear Motor

Mounted on the rear axle. Provides independent rear electric torque — this is the capability differentiator that makes the 4XE genuinely interesting for off-road use. In EV mode or hybrid mode with low-speed torque demand, the rear motor can deliver torque directly to the rear axle independently of the front powertrain.

On technical terrain at low speeds, this translates into something concrete: you can have precise rear axle torque without slipping the front drivetrain. Electric motors produce maximum torque at zero RPM — no need to "find" torque by maintaining engine RPM or slipping a torque converter. The result on a rock ledge or in a rut is smoother, more controlled power delivery than the gas-only Wrangler.

EV Capability on Trail

In Rock Crawl mode (4Lo + electric power) on a Rubicon 4XE with lockers engaged, the electric motors' instant torque and fine modulation is a real advantage over a purely gasoline-powered Wrangler. This is not marketing language — it reflects how electric motors actually behave differently from internal combustion engines under low-speed load.

The caveat is battery depletion. The 17.3 kWh pack depletes faster under sustained high-load off-road driving than it does in normal commuting. Plan for the gasoline engine to carry the workload on longer trail runs. EV capability is most useful for technical sections — rock gardens, precise line selection, approach-and-crawl situations — not as the exclusive power source for a full day on trail.

Drive Modes

Charging

The charging connector is SAE J1772 — the standard North American plug used by most non-Tesla EVs and PHEVs. For someone commuting 20–25 miles round-trip, the 4XE can cover the full commute on electricity and arrive home with a Level 2 charge needed overnight. That's the scenario where the 4XE's economics work well.

The 2.0L Turbocharged Engine

The gasoline engine is a 2.0L inline-4 with a turbocharger — the same engine available as a standalone option on non-hybrid JL Wranglers. On its own it produces approximately 270 hp; combined with the electric motors, the system delivers approximately 375 hp total.

The engine starts automatically when the battery is depleted, when heavy throttle is requested, or when the system needs it for thermal management (including FORM mode). In normal EV or hybrid driving, the engine may not run at all on short trips — which has implications for oil condition. See the Common Problems guide on FORM mode and oil change intervals for PHEV-specific service considerations.

The 2.0T has one documented weak point: the oil cooler seal on 2021–2023 examples. When the seal fails, oil can enter the coolant circuit. The repair is warranty-covered, but the seal has been known to fail again after initial replacement. If you're evaluating a used 4XE with this engine, ask for any oil cooler service history.

FORM Mode — What Every 4XE Owner Should Know

FORM stands for Fuel and Oil Refresh Mode. If the 4XE is driven primarily on electricity and the gasoline engine rarely runs, the engine oil can degrade — heat cycling without adequate circulation affects its condition. FORM mode forces the ICE to run until oil temperature reaches a set threshold, keeping the oil in good condition even when EV usage means the engine goes long stretches without running.

This is a legitimate engineering solution to a real PHEV maintenance challenge. The problem: after the fire recall remedy on some vehicles, the FORM mode trigger became stuck. Affected vehicles default to FORM mode and cannot exit it — EV capability is disabled, the vehicle runs on gasoline only, and fuel economy drops to standard Wrangler levels.

Verdict