ECM J1939 CAN Bus Communication Lost
What does PERKINS-247-9 mean?
The PERKINS-247-9 (Kohler RDC2) diesel fault code means: ECM J1939 CAN Bus Communication Lost. This is a serious severity code.
Common Symptoms
- Panel displays fault code 247-9 and may show a red or amber alarm light
- Generator refuses to start or shuts down immediately after cranking
- PowerWizard 1.1 or 2.0 screen shows 'ECM Communication Lost' or similar CAN fault message
- Engine speed, oil pressure, and coolant temperature readings disappear from the controller display
- Remote monitoring via OnCue or Mobile Link loses live engine data
- Automatic start attempts during a power outage fail with no crank or immediate stop
- Perkins EST cannot connect to the ECM over the service port during the fault
Probable Causes (Ranked by Likelihood)
- Damaged, corroded, or loose J1939 CAN bus wiring connector at the ECM or controller harness plug Very Likely
- Open or shorted CAN High / CAN Low wires between the ECM and the PowerWizard or genset controller Very Likely
- Missing or failed 120-ohm CAN bus termination resistor at one or both ends of the network Likely
- ECM power supply fault (low battery voltage or blown fuse on the ECM supply circuit) causing the ECM to drop off the CAN bus Likely
- Failed or corrupted ECM firmware preventing normal J1939 message transmission Possible
- Controller (PowerWizard or equivalent) internal CAN transceiver failure Possible
- Moisture or contamination inside the engine wiring harness causing intermittent CAN bus short Less Likely
Step-by-Step Diagnostic Procedure
Step 1 -- Safety first. Set the panel switch to OFF and disconnect battery negative before touching any wiring. Wait 30 seconds for capacitors to discharge.
Step 2 -- Inspect the J1939 CAN connector at the ECM (usually a Deutsch or AMP connector on the engine valve cover side). Look for bent pins, corrosion, moisture, or a connector that is not fully seated. Push the connector firmly until it clicks and recheck.
Step 3 -- Trace the CAN harness from the ECM to the PowerWizard or genset controller. Look for chafed insulation, pinched sections, or burn marks. Pay close attention anywhere the harness passes over hot exhaust components or through a bulkhead grommet.
Step 4 -- With battery reconnected and everything powered OFF (engine not running), set your multimeter to resistance (ohms). Measure across the two CAN bus pins (CAN High and CAN Low) at the controller harness connector. A healthy J1939 network reads approximately 60 ohms (two 120-ohm termination resistors in parallel). A reading of 120 ohms means one terminator is missing or open. A reading near 0 ohms means you have a short. Infinity means the circuit is open.
Step 5 -- Locate the termination resistors. On most FG Wilson packages one resistor is inside the PowerWizard controller and one is at the far end of the CAN network, often inside a junction box near the engine. If you find a resistor that is physically damaged or reads out of spec (should be 120 ohms each when measured individually with the harness unplugged), replace it. This is a standard 120-ohm 0.25W resistor or a plug-in CAN terminator available from electrical suppliers.
Step 6 -- Check ECM supply voltage. With the panel in the RUN position, measure DC voltage at the ECM main supply fuse or relay output. It should read 24V DC (or 12V DC on smaller sets) within 0.5V of battery voltage. A voltage below 20V on a 24V system means a charging or wiring problem that can starve the ECM and drop it off the CAN bus. Check the ECM fuse (typically 10A or 15A in the engine harness fuse block) and replace if blown.
Step 7 -- If wiring and power supply check out, reconnect everything and attempt to connect a laptop running Perkins EST to the ECM service port. If EST also fails to connect, the ECM itself may have a failed CAN transceiver or corrupted firmware. This step requires Perkins EST and dealer-level credentials. Call a Perkins service dealer at this point.
Step 8 -- If EST connects but the PowerWizard still shows the fault, suspect the controller CAN transceiver or a configuration mismatch. A Perkins or FG Wilson dealer can re-flash the controller or ECM to resolve firmware-level CAN incompatibilities.
Frequently Asked Questions
What does Perkins code 247-9 mean?
Code 247-9 means the genset controller (usually a PowerWizard 1.1 or 2.0) has stopped receiving J1939 CAN messages from the Perkins ECM. The ECM is the engine's main computer, and the controller needs to talk to it constantly to monitor protection parameters and send run or stop commands. When that communication link goes silent, the controller declares fault 247-9 and will not allow the engine to run, because it cannot confirm that the engine is safe to operate.
Can my generator still run with this code active?
No. This fault blocks the start sequence entirely or causes an immediate shutdown. Because the controller cannot read oil pressure, coolant temperature, or engine speed over the CAN bus, it has no way to protect the engine from damage. Most PowerWizard-equipped sets are designed to fail safe and will not crank until 247-9 is cleared.
How much does it cost to fix Perkins 247-9?
If the problem is a loose connector or a cheap termination resistor, a confident DIYer can fix it for $10 to $80 in parts. If the harness is damaged and needs professional repair, expect $200 to $600 for a technician visit and labor. In the worst case, where the ECM itself has failed, parts plus programming can run $800 to $2,500 depending on the engine series.
Will the generator start the next time the power goes out?
Not while this code is active. The automatic transfer switch (ATS) will still sense the utility outage and send a start signal to the generator, but the PowerWizard controller will refuse to crank the engine until the 247-9 fault is resolved. Treat this as an emergency repair, not a watch-and-wait situation, especially on a standby set protecting critical loads.