U1736 – SCP (J1850) Lack of Acknowledgment for Telltales

The ODBII code U1736 SCP (J1850) indicates a communication issue where the vehicle’s control module is not receiving an acknowledgment signal from the telltale system, which is responsible for warning lights and indicators on the dashboard.

The severity of ODBII code U1736 SCP (J1850) Lack of Acknowledgment for Telltales is moderate.

Common Causes For: U1735 U1735: “Module Communication Failure”

• Faulty communication between modules
• Damaged wiring or connectors
• Malfunctioning telltale indicators
• Software issues or bugs in the module
• Low battery voltage or power supply issues
• Corroded or loose ground connections
• Faulty instrument cluster or dashboard assembly

Common misdiagnosis for U1736 SCP (J1850) Lack of Acknowledgment for Telltales

• Faulty instrument cluster
• Wiring issues or shorts
• Faulty body control module (BCM)
• Communication network problems
• Defective telltale lights
• Software glitches in the vehicle’s computer systems
• Battery or power supply issues

Common Troubleshooting Steps

The OBD-II code U1736 indicates a communication issue related to the SCP (Serial Communication Protocol) on the J1850 bus, specifically concerning the lack of acknowledgment for telltales. This can affect the vehicle’s ability to communicate with various modules, particularly those responsible for dashboard indicators and warning lights. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Addressing other related codes may help resolve the U1736 code.
• Inspect Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors associated with the telltale circuit for any signs of damage, corrosion, or loose connections.
• **Continuity Test: Use a multimeter to test for continuity in the wiring. Look for breaks or shorts in the wires.
• Check the Telltale Modules: Identify the specific modules responsible for the telltales (e.g., instrument cluster, body control module).
• Ensure that these modules are functioning correctly. If possible, test them in another vehicle or replace them temporarily to see if the issue resolves.
• Inspect the J1850 Bus: **Bus Communication: Use a scan tool to monitor the J1850 bus for proper communication. Look for any irregularities in data transmission.
• **Termination Resistors: Ensure that the J1850 bus has the correct termination resistors in place. A missing or faulty resistor can cause communication issues.
• Check for Ground Issues: Ensure that all ground connections related to the modules and the J1850 bus are secure and free of corrosion. Poor grounding can lead to communication failures.
• Test the Battery and Charging System: A weak battery or charging system can cause voltage fluctuations that affect module communication. Test the battery and alternator to ensure they are functioning properly.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect and see if the code reappears.
• Update Software/Firmware: Check if there are any software updates available for the vehicle’s modules. Sometimes, manufacturers release updates to fix communication issues.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1736 code or telltale communication issues 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 mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these troubleshooting steps, you should be able to identify and resolve the underlying cause of the U1736 code.