U0253: Lost Communication With Accessory Protocol Interface Module

What it means

A control module has stopped receiving expected messages from the accessory protocol interface module. The code identifies the communication loss; accessory functions routed through that module may be affected.

How it works

The accessory protocol interface module routes or manages accessory communications, which may include infotainment functions depending on the vehicle. U0253 sets when another module stops receiving the expected network messages from that interface module; it does not identify which accessory feature has failed.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Accessory or infotainment functions routed through the module may be unavailable
• A communication fault or warning may appear depending on the vehicle

How to diagnose it

1. Scan all modules and save freeze-frame and network data to identify the reporting module and any related communication codes.
2. Check which accessory or infotainment functions routed through the interface module are unavailable and note any displayed warnings.
3. Inspect the interface module's connector and accessible bus wiring for looseness, corrosion, damaged pins, or harness damage.
4. Verify the module's power and ground using the manufacturer's procedure.
5. Test the network wiring to the interface module for opens or shorts using the vehicle wiring diagram.
6. If wiring and supplies are correct, follow the manufacturer's communication checks before considering module replacement.

Common fixes

• Reseat and secure a loose interface-module connector.
• Repair damaged or corroded network wiring or connector terminals.
• Restore a failed module power feed or ground.
• Replace the accessory protocol interface module only after its wiring and supplies test correctly.

Can I keep driving?

The code may disable accessory or infotainment functions routed through the interface module, but it does not by itself indicate an engine fault. Avoid trying to operate unavailable controls while driving, and check whether any affected feature is needed for safe vehicle operation.