Code j1850 Displayed on Instrument Panel of Vehicle [Troubleshoot]

The j1850 is a bus for diagnostics and data sharing. If you see the code displayed on dashboard there could be few issues.

Problem causes:

  • Loose fuse
  • Bad ground
  • Bad ignition key switch
  • Battery voltage low
  • Short to ground


You should get a OBD2 reader to find out more. OBD means on board diagnostics for vehicle self diagnostics as in this video:

There is a interface on a obd2 connector.

Engine codes begin with a P and those will help you find the exact problem.



The J1850 protocol has two variations:

  1. J1850 VPW (Variable Pulse Width): This protocol is primarily used by General Motors vehicles. It operates at a data rate of 10.4 kbps (kilo-bits per second) and utilizes a single wire for communication.
  2. J1850 PWM (Pulse Width Modulation): This protocol is primarily used by Ford vehicles. It operates at a data rate of 41.6 kbps and utilizes two wires for communication.

If you are experiencing issues with your vehicle’s communication network or have trouble connecting a scan tool, consider the following steps:

  1. Inspect the OBD-II port: Check the OBD-II port for any signs of damage, corrosion, or bent pins. Repair or replace the port if necessary.
  2. Check the diagnostic scan tool: Ensure that your diagnostic scan tool is compatible with your vehicle’s communication protocol (J1850 VPW or J1850 PWM). Also, check the scan tool’s cable and connector for any signs of damage or wear.
  3. Inspect the wiring and connections: Check the wiring and connections between the OBD-II port and the vehicle’s ECM for any signs of damage, corrosion, or loose connections. Repair or replace any damaged wiring or connectors as necessary.
  4. Check for related DTCs: Use the diagnostic scan tool to read any stored fault codes related to communication issues. These codes may provide additional information about potential problems in the vehicle’s communication network.





  • Identify the issue: Determine if you have a communication error, an issue with the diagnostic tool or software, or a problem with a specific sensor or module in the vehicle.
  • Check the diagnostic tool: Ensure that your OBD scanner or diagnostic tool is compatible with the J1850 protocol and is functioning correctly. Some tools may require a software update or configuration changes to work with J1850.
  • Inspect the OBD connector: Check the OBD-II port in your vehicle for damage or debris that could interfere with the connection. Ensure that the pins in the connector are not bent or broken.
  • Verify power and ground: Ensure that the vehicle’s battery is charged and that there is a good ground connection to the OBD-II port. Use a multimeter to check for voltage at the appropriate pins on the OBD connector.
  • Check for fault codes: Use your diagnostic tool to scan for any stored diagnostic trouble codes (DTCs) in the vehicle’s systems. These codes can provide valuable information about the cause of the issue.
  • Inspect wiring and connections: Examine the wiring and connections related to the J1850 communication network for damage, corrosion, or loose connections. Pay particular attention to the wires connecting the OBD-II port, the powertrain control module (PCM), and other relevant modules.
  • Perform a continuity test: Use a multimeter to check the continuity of the communication wires in the J1850 network. If there is no continuity, you may have a break in the wiring that needs to be repaired.
  • Check the modules: If the wiring and connections appear to be in good condition, there may be an issue with one of the modules on the J1850 network. Disconnect each module one at a time and see if the communication issue resolves. If it does, the disconnected module could be the source of the problem.