Komatsu Dump Truck DB2RKR Fault Code: CAN Communication (Engine Controller): Communication Disabled
Also called (CAN Communication (Engine Controller): Communication Disabled), CAN Communication (Engine Controller): Communication Disabled (Between Engine Controller - Transmission Controller), CAN Communication (Engine Controller): Communication Disabled (Between Engine Controller Transmission Controller) (Engine Controller System), CAN1 Discon (Engine Con), CAN1 Disconnection (Engine Controller), Trouble In CAN Communication (Engine Controller) (Transmission Controller System), Trouble in CAN Communication, Trouble in CAN Communication (Engine Controller)
CAN Communication (Engine Controller): Communication Disabled · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
DB2RKR (action code E03, also seen as action level L03) means the transmission controller or monitor controller has stopped receiving updated data from the engine controller over the CAN1 communication line. The transmission holds its current gear, forces neutral, and sets off the centralized warning lamp and buzzer. This is a communication fault, not necessarily an engine fault, but the truck loses engine speed and coolant temperature data and some functions stop working.
High severity. The transmission controller locks into neutral and keeps the current gear speed until the fault is addressed, which affects drivability and could strand the truck in operation. It is not an immediate engine-damage event, but it stops normal transmission control and hides engine coolant temperature and speed readings, so it should be diagnosed before continued hauling.
What does Komatsu Dump Truck error code DB2RKR mean?
DB2RKR sets when the transmission controller (or monitor controller, depending on the affected system) can no longer recognize the engine controller on the CAN1 communication line, known as KOMNET/r. In plain terms, the engine controller has either stopped talking or its messages are not getting through, so the rest of the machine loses access to engine data.
When this happens, the transmission controller keeps whatever gear speed it was already in and forces the gearshift lever position to neutral to keep the transmission safe. The centralized warning lamp comes on and the buzzer sounds. On the monitor side, the engine coolant temperature gauge pointer disappears from the screen and the engine speed meter needle drops to zero, since that data no longer updates.
Importantly, if DB2RKR is displayed, it confirms CAN communication is still working correctly between the transmission controller and the machine monitor. That rules out a short circuit, ground fault, or hot short in that communication line. The break is specifically between the engine controller and the rest of the CAN network, or in the engine controller itself.
Common causes of DB2RKR
- Blown fuse in the circuit feeding the engine controller or its CAN network
- Defective engine controller, including an internal short circuit (left bank or right bank on multi-bank engine setups)
- Defective power supply to the engine controller, including a defective circuit breaker (FuA1) or fuse (BT2)
- Defective CAN terminating resistor with an internal open or short circuit
- Disconnection or short circuit in the wiring harness, including wire breakage or a bad connector contact
- Ground fault in the wiring harness from contact with a ground circuit, or a hot short from contact with a 24V circuit
- Defective ACC signal from the starting switch, so the start of CAN communication is never detected
- Defective battery or defective transmission, retarder hoist, air conditioner, or monitor controller
- Defective payload meter controller or KOMTRAX terminal on machines equipped with one
How to troubleshoot Komatsu Dump Truck DB2RKR: first checks
- Turn the starting switch to the ON position, this is the listed method for reproducing the fault code, and watch whether the warning lamp and buzzer activate and whether the coolant temperature gauge and speed meter drop out
- Write down every other failure code displayed at the same time, especially any code beginning with D or ending in RKR, since these point toward which side of the CAN network has the problem
- Check the fuses and circuit breaker (FuA1) for the engine controller power supply, and check fuse BT2, for blown or tripped conditions
- Inspect wiring harness connectors for the engine controller and CAN network for corrosion, loose pins, or wire breakage, since power to the controllers remains live from the battery even with the starting switch off
- Check the CAN terminating resistor, located in the monitor controller on the operator cab side, with a second connector on the engine side, for internal open or short circuit
- Do not try to check active CAN signals with a multimeter, since the communication line runs on pulse voltage, not a steady voltage a multimeter can read
How the code clears
No separate reset procedure is listed for this code. The listed method to reproduce or confirm it is simply cycling the starting switch to the ON position and observing whether the warning lamp, buzzer, and gauge behavior return. Once the underlying wiring, fuse, terminating resistor, or controller issue is repaired, the code should stop resetting on its own during normal CAN communication startup.
Affected models and serial ranges
DB2RKR appears in our records across 8 Komatsu Dump Truck models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| HD325 | Serial range not listed in source records |
| HD405 | Serial range not listed in source records |
| HD465 | Serial range not listed in source records |
| HD605 | Serial range not listed in source records |
| HD785 | Serial range not listed in source records |
| HM300 | Serial range not listed in source records |
| HM350 | Serial range not listed in source records |
| HM400 | Serial range not listed in source records |
Frequently asked questions
What does Komatsu fault code DB2RKR mean?
It means the transmission controller, or in some versions the monitor controller, cannot recognize the engine controller over the CAN1 communication line. Data updates from the engine controller have stopped, so the transmission holds its current gear and forces neutral while warning lights and a buzzer activate.
Is DB2RKR a serious problem?
It is serious enough to address before continuing normal hauling operations. The transmission is forced into neutral and stays at its current gear speed, and engine speed and coolant temperature data disappear from the monitor screen, so the operator loses important information.
Can I diagnose DB2RKR with a multimeter?
Not for the active CAN signal itself. The communication line runs on pulse voltage while the system is operating, so a standard multimeter cannot measure it. Diagnosis instead focuses on fuses, circuit breakers, wiring harness continuity, connector condition, and the terminating resistor.
Does DB2RKR mean the CAN wiring has a short circuit or ground fault?
Not necessarily, and in fact the opposite in one sense. The presence of DB2RKR confirms that CAN communication is still working correctly between the transmission controller and the machine monitor, which rules out a short circuit, ground fault, or hot short circuit on that particular line. The problem lies specifically with the engine controller side of the network.
What other codes should I check if I see DB2RKR?
Write down every other failure code displayed at the same time. Codes such as those beginning with D or ending in RKR, including DB2QKR, DAQRKR, or DB1RKR, along with DBBQKR, are noted as related codes that can help narrow down which part of the CAN network or which controller is causing the disconnection.
Will the truck still drive with DB2RKR active?
The transmission controller keeps the current gear speed and forces the gearshift lever into neutral to protect the driveline, which limits normal operation. The engine itself may still run, but engine speed and coolant temperature cannot be displayed or detected by the affected controllers.
What causes the engine controller to disappear from the CAN network?
Listed causes include a blown fuse, defective power supply or circuit breaker (FuA1) to the engine controller, a bad CAN terminating resistor, harness wiring that is open, shorted, or grounded, a defective ACC signal from the starting switch, or an internal fault in the engine controller itself.