An Error Code 187 indicates that there has been a severe communication breakdown between the VECU 21358126, and the excavator EC290B. This will not allow operation until this issue has been resolved. The fault associated with this code is caused by the Vehicle Electronic Control Unit (V-ECU); typically it is shown as 187 PSID 200-9 which indicates that the V-ECU has lost its communication with the Control Module.
What It Means Technically
The code: MID 187, PSID 200, FMI 9 indicates that the vehicle electronic control unit (V-ECU) is not communicating with the engine control module (ECM) through the J1939 data link. V-ECU, which can be found in the cab and/or frame, is responsible for controlling many functions of the vehicle, including hydraulics and transmission. To properly perform these functions, the V-ECU needs engine data for timing purposes.
While 21358126 is the pilot control joystick, a short circuit or improper grounding within its harness can disrupt the CAN-bus network. A severed link triggers a protective shutdown. Common culprits include cut harness wires, corroded connectors, or a blown fuse supplying power to linked modules.
Root Causes
- Wiring Problems – Pinched/snapped wires/terminals due to maintenance performed on the boom, create issues with signal delivery.
- Power Problems – Lack of voltage due to damaged fuse (often misdiagnosed on previous service), typically in projects where voltage required checking.
- Connector Problems – Loose connectors or corrosion in the J1939 backbone (caused by accumulated dust and vibrations in rough terrain).
- Module Problems: Occasional intermittent signal errors (FMI 2 variation) are caused by V-ECU module internal failure or sensor interference from the joystick unit..
Diagnosis Steps
- Inspect the J1939 harness from V-ECU to engine for continuity using a multimeter; check for exactly 60 ohms across CAN High/Low pins (two 120-ohm resistors in parallel).
- Disconnect Joystick 21358126 to see if the communication error clears, indicating an internal component short.
- Scan with Volvo Diagnostic Tool (VDT) to clear code and monitor live data for reconnections.
- Test battery voltage (should stay 24V nominal) and alternator output to rule out supply drops.
To resolve error code 187, you need to look at more than just the 21358126 joystick and make sure that the whole J1939 digital network is properly powered and physically connected. Once the 5v reference and 60 ohms resistance are restored your Volvo Excavator will have the seamless communication needed to return to work.
