Techline Connect Error Codes E4399 / UEH101 - Diagnostic Procedure

Overview - Techline Connect E4399 / UEH101 errors

Error codes E4399 and UEH101 in Techline Connect are typically caused by communication faults on the GM vehicle network. These errors indicate the programming tool cannot establish a stable connection with the target module. E4399 indicates a module programming failure and UEH101 indicates the tool is unable to establish module communication.

Note: U codes (communication DTCs) are almost always the root cause of E4399 / UEH101 failures. Always scan for and address all U codes before attempting any module reprogramming attempting to reprogram while U codes are active will result in repeated E4399 / UEH101 failures.

Error code reference

- E4399 - Module programming failure. Likely cause: network communication fault, U codes present.
- UEH101 - Unable to establish module communication. Likely cause: module may be faulty or network interruption.

Diagnostic procedure

Follow the six-step procedure below in order. Do not skip ahead to reprogramming until each phase is confirmed complete - skipping the U code repair step is the number one cause of repeated E4399 / UEH101 failures.

Step 1 - Scan vehicle for all DTCs

Connect a scan tool to the vehicle and perform a full system scan. Record all codes before clearing anything.

- Connect scan tool to OBD-II port.
- Run a complete all-module scan.
- Print or record all stored and pending DTCs.

Step 2 - Check for U codes

Review the scan results specifically for U codes. U codes are communication-related diagnostic trouble codes that indicate a fault on the vehicle's data network (CAN bus, LIN bus, etc.).

If ANY U codes are present, they must be resolved before attempting module reprogramming. Attempting to reprogram while U codes are active will result in repeated E4399 / UEH101 failures.

Step 3 - Address all U codes

Diagnose and repair each U code before proceeding. Common causes include:

- Damaged or corroded wiring in the CAN network.
- Loose or damaged module connectors.
- Faulty terminating resistors.
- Module(s) drawing excessive current on the network.
- Battery voltage issues causing intermittent communication loss.

Step 4 - Clear codes and rescan

After addressing all identified U code causes:

- Clear all DTCs from all modules.
- Cycle ignition off and wait 30 seconds.
- Perform a full system rescan.
- Verify no U codes return - if they do, repeat Step 3.

Do not proceed to reprogramming until the rescan confirms the network is clean.

Step 5 - Reattempt module reprogramming

Once all U codes are resolved and the network is clean, return to the Techline Connect reprogramming procedure for the target module. With the communication faults cleared, the E4399 / UEH101 errors should no longer appear.

Step 6 - Verify module access if reprogramming still fails

If reprogramming still fails after a clean rescan, check whether the scan tool can communicate with other modules on the vehicle. This is a critical diagnostic question:

- Yes - other modules accessible: The target module is likely faulty. If reprogramming continues to fail, the module should be replaced.
- No - cannot reach other modules: Network communication issue still present. Recheck wiring, connectors, and bus integrity before proceeding.

Quick reference summary

Follow these steps in order. Do not skip ahead to reprogramming until each phase is confirmed complete:

- Step 1 - Connect scan tool and run full scan. Expected outcome: all module DTCs recorded.
- Step 2 - Check for U codes. Expected outcome: identify all communication faults.
- Step 3 - Diagnose and repair U code causes. Expected outcome: network communication restored.
- Step 4 - Clear codes and rescan. Expected outcome: no U codes on rescan.
- Step 5 - Reprogram target module. Expected outcome: programming completes without error.
- Step 6 - Verify all-module access. Expected outcome: all modules communicate normally.

Contact AE Solutions for support

For additional help with Techline Connect E4399 / UEH101 errors, GM network diagnostics, or module reprogramming questions, contact AE Solutions:

- Phone: 913-856-6678
- Website: https://aesolutions.us - Submit a support ticket online