U0294: Lost Communication With Powertrain Control Monitor Module

What it means

A second powertrain control module (e.g. on dual-engine, twin-turbo bank-specific or range-extender vehicles) has dropped off the network. Engine power is reduced or limp-home mode is forced.

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

This code concerns the second powertrain control monitor module, sometimes used where a vehicle has multiple engine or powertrain controllers. The network sets the code when expected messages from that module stop arriving, which can reduce engine output or trigger a limp-home strategy.

Common causes

Most likely first.

1. PCM B 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 for freeze-frame information and communication codes to confirm whether the second powertrain monitor module alone is missing or the wider network is affected.
2. Check whether the engine runs with reduced power and note any warning messages, then verify that other powertrain modules can still communicate.
3. Inspect the second module's connector and harness for looseness, corrosion, water or damage, and check for recent work that may have disturbed its wiring.
4. Check the module's specified power and ground, then test the network wiring and gateway connections for opens, shorts or routing problems using the wiring diagram.
5. If wiring and supplies are sound, have network termination and module operation checked to the manufacturer's specifications; do not assume a resistor fault without measurement.

Common fixes

• Reconnect or repair a loose, corroded or damaged connector at the second powertrain monitor module.
• Repair a confirmed open or short in the module's network wiring.
• Restore the module's specified power or ground by repairing the identified supply fault.
• Correct a gateway routing fault if testing confirms messages are not being forwarded to the second module.
• Repair network termination or replace the module only when testing to manufacturer specifications identifies that fault.

Can I keep driving?

If the engine is in limp mode, avoid high speeds, steep climbs and towing, and drive only far enough to reach a safe place for repair. Stop if power loss makes it unsafe to keep pace with traffic, since the vehicle may reduce output further or shut down affected functions.