IEM (ERAD Inverter) Repair Service

Volvo Hybrid / Plug-in Hybrid (rear electric axle drive)

The Inverter Electric Rear Axle Drive Module (IEM) controls the electric rear drive axle (ERAD). It converts 400 V DC into three-phase 400 V AC to drive the rear electric motor, and converts back to DC during regenerative braking. The IEM is mounted behind the rear axle, typically on a bracket beside the Onboard Charger (OBC).

What the IEM Controls

• Provides rear electric drive during electric and hybrid operation
• Recharges the high-voltage battery during braking (regenerative braking)
• Supports high power demand during all-wheel-drive operation
• Creates engine-braking style properties when releasing the accelerator pedal

Common Fault Symptoms

• Loss of rear electric drive / reduced AWD performance
• Hybrid system warnings or “propulsion system” messages
• No regenerative braking from rear axle / unusual braking feel
• Intermittent drivetrain faults (especially under load)
• Stored diagnostic trouble codes related to ERAD / IEM communication or inverter performance

Module Connections (Technical Overview)

The IEM has three main connectors:

• AC power connector (three-phase)
• DC power connector (high-voltage DC)
• Signal connector (vehicle / engine communication)

It communicates on the vehicle network as a CAN slave and is directly connected to key high-voltage components including the ERAD, BECM, and OBC. The module also monitors itself continuously using an internal diagnostic system.

Repair Service Notes

This listing is for a repair service. If the IEM becomes non-operational, Volvo’s official route is often full unit replacement, and the replacement typically requires calibration using VIDA. Where repair is viable, we aim to restore proper operation and reliable communication with the vehicle systems.

We strongly recommend having this work carried out by professionals due to the high-voltage and drivetrain integration. The IEM is part of the 400 V high-voltage system and is located under the vehicle near the rear axle.

• High-voltage safety procedures are mandatory before any removal or refit.
• Incorrect handling can cause serious injury and/or damage to the IEM, ERAD, or HV battery system.
• The IEM interacts with torque requests from the ECM and rotor position feedback from the ERAD, so correct diagnosis matters.

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