Fix U0146: Mechanic’s solutions that WORKED

The U0146: Lost Communication With Gateway Module ‘A’ code signifies a communication breakdown with the Gateway Module ‘A’. This module is part of the vehicle’s Controller Area Network (CAN), which facilitates the exchange of operating information and commands among automotive devices without a host computer. The malfunction indicated by this code occurs when the CAN bus, which operates on a differential voltage system, fails to receive periodic messages from the Gateway Module ‘A’, leading to potential operational issues in the vehicle.

U0146 quick overview

Description	U0146: Lost Communication With Gateway Module ‘A’
Is it serious?	This code is serious, with a repair importance level of 3/3, indicating potential significant impacts on vehicle operation.
Possible causes	– Faulty Gateway Module ‘A’ – Gateway Module ‘A’ harness is open or shorted – Gateway Module ‘A’ circuit poor electrical connection
How to diagnose?	Inspect Gateway Module ‘A’: Check for any faults or damage to the Gateway Module ‘A’. Examine Wiring and Connectors: Look for open, shorted, or poorly connected wiring and connectors in the module’s circuit. Check for Damaged Components: Identify any broken, bent, pushed out, or corroded connector pins and other components.

How to fix U0146 – learn from mechanics

I looked into U0146 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle Information: 2016 Ford F-150 Platinum 3.5L – Blind Spot Indicator System, Cross Traffic Alert issues.

Issue + Repair History:

• Customer reported “Blind Spot detection off” and “Cross Traffic Alert off” messages.
• Radio and HVAC controls became unresponsive.
• All four windows and running boards not functioning.
• Right rear tail light housing cracked and filled with water.
• Rusted connector to BLIS sensor.
• Replaced sensor and tail light housing, cleared codes.
• Persisting issues with running boards and front control interface module.

Other OBD2 Codes + Test Results:

• B109F-97: Intrusion Sensor module obstructed.
• U256-00: Lost Communication with front controls interface module A.
• U0146-00: Lost Communication with Gateway A.

Suggestions to Fix Issue:

• Check for hard faults or continuous memory in the codes.
• Perform a network test to assess module responses.
• Disconnect and reconnect battery cables, short them together to reset.
• Clear all DTCs and retest network.
• Consider potential issues with BLIS radar sensor connector.
• Program the replaced right rear SOD-R module.
• Inspect for blown fuses and review wiring diagrams.
• Investigate potential network traffic issues.
• Check for bad splices in the harness under the driver’s seat carpet.

Final Fix:

• No blown fuses were found.
• Disconnected battery cables and connected them together for 30 minutes; no change.
• Mobile programming technician updated and programmed right rear BLIS module, added VIN.
• Discovered running boards setting turned off in vehicle dash settings.
• Adjusted running board settings to automatic, resolving all issues.
• Customer incurred costs for lens, BLIS module, labor, and programming.

Case #2: Toyota

Vehicle Information: 2005 Toyota Prius 1.5L – MIL lamp on, communication issues.

Issue + Repair History:

• Initially diagnosed with fault P0A7F (Battery pack deteriorating).
• Communication problems when connected to Techstream; vehicle shuts down.
• No issues when using generic or Snap-on scanners; CAN-bus related codes detected.
• Tested leads at DLC3 connector; signal and chassis ground ohms slightly high.
• Car had minor collision repair on the passenger front corner.

Other OBD2 Codes + Test Results:

• U0073: Control module communication.
• U0121: Loss communication with ABS module.
• U0146: HV loss of communication with Gateway A.
• U0129: Lost communication with brake control module.
• U0111: HV Loss communication with battery control module.
• U0100: Loss of control with ECM/PCM.
• V0293: Lost communication with Hybrid Vehicle Control System.
• P0A1D: Hybrid Power Control module communication.

Suggestions to Fix Issue:

• Test 12-volt battery and replace if necessary.
• Inspect fuse box/harness in the left front for damage or corrosion.
• Check Techstream interface configuration and CAN speed settings.
• Measure resistance of CAN bus at DLC3 connector.
• Verify if there’s 12v on pins 6 or 14 of DLC3, indicating potential water in a connector.
• Check auxiliary battery ground at the back of the body.
• Consider individual cell replacement in the HV battery.

Final Fix:

• The problem was traced to the DLC connector.
• Discovered a 10K ohm short from B+ve pin 16 to Can bus Hi & Lo.
• Cleaning the pins in the DLC connector resolved communication issues.
• Techstream confirmed the HV battery was deteriorating.
• Reiterated the importance of using Techstream and Fluke for accurate diagnostics on Prius.

Case #3: Cadillac

Vehicle Information: 2010 Cadillac STS 3.6L – Issues with ECM, TCM, EBCM, and GMLAN High Speed Communication.

Issue + Repair History:

• Initially came for oil change and check engine light; misfire codes and history P0008 detected.
• Repairs included spark plugs, timing chain, VVT actuators with updated thrust washers, and induction service.
• U codes stored in ECM, TCM, and EBCM not investigated initially.
• Customer returned with vehicle in reduced power mode, and codes related to communication with ECM, TCM, and EBCM were found.
• No aftermarket components affecting communication lines were found.
• Pins for GMLAN communication lines checked and found without corrosion or fretting.
• Reprogramming of ECM, TCM, and EBCM performed without resolving the issue.

Other OBD2 Codes + Test Results:

• ECM: P0700 (Trans Mil request ON), P2544-00 (Transmission Torque Request).
• TCM: U0100 (lost communication with ECM).
• EBCM: U0100-00 and U0146-00 (lost communication with ECM and Gateway A).

Suggestions to Fix Issue:

• Load test ECM power and ground circuits.
• Check for noise on data lines using a scope, particularly during gear changes or heavy throttle.
• Consider unplugging EBCM and driving to see if it affects communication.
• Inspect for shorted or broken wires, and check all grounds.
• Examine resistance on the high-speed circuit at the DLC, and ensure it’s within normal ranges.
• Investigate modules on the CAN circuit for common disconnects.

Final Fix:

• No communication detected from the radio/navigation unit.
• Replaced the radio/navigation unit, but it was defective.
• ECM and EBCM replaced without resolving communication codes.
• Erratic speedometer operation and flickering warning lights observed during a test drive.
• A wiggle test led to the discovery of communication issues in the ECM.
• Replaced the high-speed communication wire, resolving the issue.

Case #4: Dodge

Vehicle Information: 2009 Dodge Journey SXT 3.5L – No Start, multiple configuration and communication errors.

Issue + Repair History:

• Vehicle arrived with a used IPDM installed and disassembled components under the hood.
• Different VIN in the body control module (BCM).
• “Bad key” message displayed; new key and PIN programming unsuccessful.
• WIN module showed incomplete key programming.
• Multiple configuration codes from different modules related to VIN mismatch and invalid key.
• WIN module suspected to be faulty.

Other OBD2 Codes + Test Results:

• ECM: P0513 (invalid SKIM).
• ABS: C2206, U140E, C2202 (vehicle configuration and VIN mismatch).
• Airbag Module: B222A, B223B, U1415, U1414 (vehicle mismatch, configuration missing/implausible).
• Wireless Control Module: B1A25, B2229, B1A29, U1197, B1A27 (invalid key, SKREEM internal, SKIM mismatch, Security Seed Response not received from ECM, programming performance).

Suggestions to Fix Issue:

• Rewrite VIN in BCM (TIPM).
• Replace and reprogram BCM with a new one if necessary.
• Replace WCM and program to vehicle.
• Perform “restore vehicle configuration” in TIPM.
• Ensure correct programming procedures are followed for WIN module installation.

Final Fix:

• Replaced WIN module with two keys programmed to it.
• Vehicle started then entered immobilizer mode.
• Dealership programmed only the virgin key.
• Persistent configuration mismatch errors in ABS and BCM.
• Codes related to secret key and ECM mismatch with SKIM.
• Advised customer that replacing TIPM and ABS modules and warranting out the WIN module may be necessary.
• Despite errors, the vehicle still starts but concerns remain about potential future immobilization.

Case #5: Dodge

Vehicle Information: 2014 Dodge Challenger SXT 3.6L – No Start, no spark or injector pulse, multiple communication errors.

Issue + Repair History:

• Vehicle towed in for no start condition.
• Lack of spark and injector pulse.
• Multiple lost communication codes across various modules, including U0141.

Other OBD2 Codes + Test Results:

• U0141: Lost communication with front module (common across several modules).
• Other modules with lost communication codes include generic powertrain, anti-lock, cabin compartment node, climate control, electric power steering, master audio, occupant restraint, passive entry, transmission control.
• Wireless control module has B1A11, B1A35, B210D, U0146.

Suggestions to Fix Issue:

• Check connections, powers, and grounds at the TIPM (front control module).
• Inspect all fuses.
• Use a scope and CAN bus wiring diagram to test the network, particularly at star connectors.
• Check communication with TIPM and ensure all fuses are good.
• If no communication with TIPM, start diagnostics there.
• Make a list of modules with and without communication and proceed accordingly.

Final Fix:

• Vehicle sent to the dealer for further diagnostics and potential reprogramming.
• Specific details on the final resolution from the dealer were not provided.

Step	Action
1.	Check Technical Service Bulletins (TSBs): Begin with TSBs for your vehicle to find any known issues and fixes.
2.	Access Gateway Module: Attempt to access the Gateway module. If accessible, U0146 may be intermittent or a memory code. If not, the issue is active.
3.	Check Power and Ground: Inspect all fuses powering the Gateway module. Verify all ground connections are clean and tight.
4.	Clean Ground Connections: If necessary, clean ground connections using a wire brush and a baking soda/water solution.
5.	Clear Codes and Re-Test: After repairs, clear codes and check if U0146 returns or if communication with the Gateway module is restored.
6.	Inspect CAN Bus Connections: Locate and inspect the CAN C bus communication connections, especially the Gateway module connector.
7.	Check Connectors and Wiring: Visually inspect connectors and wiring for damage, corrosion, or wear. Clean and apply electrical grease to terminals if needed.