U1612 – SCP (J1850) Lack of Acknowledgment for Primary Id

The ODBII code U1612 indicates a lack of acknowledgment from a module on the SCP (J1850) communication network, suggesting that the primary identifier for a device is not responding as expected.

The severity of ODBII code U1612 is moderate.

Common Causes For: U1611 U1611: “Control Module Communication Fault”

• Faulty communication between modules
• Damaged or corroded wiring or connectors
• Malfunctioning or incompatible control modules
• Low battery voltage or poor power supply
• Software issues or programming errors
• Interference from aftermarket devices or modifications
• Faulty or damaged OBD-II port

Common misdiagnosis for U1612 SCP (J1850) Lack of Acknowledgment for Primary Id

• Faulty Engine Control Module (ECM)
• Wiring issues or shorts in the communication lines
• Defective or corroded connectors
• Malfunctioning sensors
• Issues with the vehicle’s battery or charging system
• Problems with the diagnostic tool or scanner
• Software or firmware issues in the vehicle’s modules
• Incorrectly configured or incompatible aftermarket components

Common Troubleshooting Steps

The OBD-II code U1612 indicates a communication issue related to the SCP (Serial Communication Protocol) on the J1850 bus, specifically a lack of acknowledgment for a primary ID. This can occur in vehicles that use the J1850 protocol for communication between various modules. Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Other Codes: Scan the vehicle for any additional trouble codes. Other codes may provide context or indicate related issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harnesses and connectors associated with the affected modules for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent, corroded, or pushed back.
• Test the Communication Bus: **Scan Tool: Use a compatible OBD-II scan tool to monitor the communication on the J1850 bus. Check if other modules are communicating properly.
• **Bus Voltage: Measure the voltage on the communication lines to ensure they are within specifications.
• Check Power and Ground: Verify that the affected module has proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• Inspect Modules: **Module Functionality: Determine if the module that is not responding is functioning correctly. If possible, test the module in another vehicle or replace it with a known good unit.
• **Reprogramming: If the module is not responding, it may need to be reprogrammed or updated.
• Look for Interference: Check for any aftermarket devices or modifications that may interfere with the communication bus, such as alarms, remote starters, or audio systems.
• Check for Short Circuits: Inspect the wiring for any short circuits to ground or to other wires that could disrupt communication.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect and see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1612 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional technician or dealership with experience in diagnosing communication issues.Conclusion Troubleshooting OBD-II code U1612 requires a systematic approach to identify and resolve communication issues. By following these steps, you can narrow down the potential causes and work towards a solution.