U01B2: Lost Communication With Planetary Gear Set Control Module

What it means

ECU lost communication with planetary gear set control module (used in some hybrid powertrains for power split).

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

The Planetary Gear Set Control Module manages or reports planetary gear set operation in some hybrid power-split drivetrains. This code sets when other controllers do not receive expected messages from that module, which can interrupt coordinated powertrain control.

Common causes

Most likely first.

1. Module unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and record freeze-frame data to identify related hybrid, transmission, or network faults.
2. Check whether the Planetary Gear Set Control Module responds to a scan tool and whether drivetrain data from it is available.
3. Inspect the module's connectors and harness for damage, corrosion, looseness, or fluid contamination.
4. Check the module's power and ground circuits under load against the manufacturer's specification.
5. If its supplies are sound, test the relevant communication wiring and gateway routing for network faults.

Common fixes

• Reconnect or repair a loose or corroded module connector.
• Repair damaged wiring or restore the module's power and ground.
• Repair a confirmed network or gateway routing fault.
• Replace the Planetary Gear Set Control Module if it fails communication checks with sound power, ground, and wiring.

Can I keep driving?

A hybrid power-split control fault can cause reduced power, abnormal drivetrain behavior, or a shutdown, so avoid driving farther than needed to reach a safe place. Do not continue if propulsion or gear engagement becomes unpredictable.