The Cummins/Onan C40 N6 is a 2.4 L 4-cylinder turbo with after cooler engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the RS 40.
Also known as: Cummins C40 N6
| Displacement | 2.4 L |
|---|---|
| Cylinders | 4 |
| Aspiration | Turbo with after cooler |
| Rated speed | 1800 rpm |
How to read your Cummins/Onan engine serial & model number →
| Code | Meaning | Cause | Remedy |
|---|---|---|---|
| 143 | Engine Oil Pressure Low (Warning) — Engine oil pressure is below the low oil pressure warning threshold. | Lubricating oil level is low | Check the oil level. Add oil, if necessary. |
| 143 | Engine Oil Pressure Low (Warning) — Engine oil pressure is below the low oil pressure warning threshold. | External leak | Inspect the engine and surrounding area for external oil leaks; Contact your local dealer if a leak is present. |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient. |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable. |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | Radiator blocked | Inspect for dirt, debris, or obstruction; Remove blockage or winterfront as applicable. |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable. |
| 151 | Engine Coolant Temperature High (Shutdown) — Engine coolant temperature has exceeded the alarm (shutdown) threshold for high coolant temperature. | Fan belt is broken or loose | Inspect belt(s) for damage, wear, and proper tension; Repair or replace if damaged or worn. |
| 155 | Intake Manifold Temperature High (Shutdown) — Engine intake manifold temperature has exceeded 203 °F (95 °C) for greater than 10 seconds. | For the troubleshooting procedure, refer to DTC 127 in the E-Controls Manual. | |
| 197 | Coolant Level Low (Warning) — Coolant level sensor signal is showing a low coolant level for greater 10 seconds. | Low coolant | Remove radiator cap and check that coolant is up to the required level. |
| 415 | Engine Oil Pressure Low (Shutdown) — Engine oil pressure is below 26 psig (180 kpa) for greater than 10 seconds. | Lubricating oil level is low | Check the oil level. Add oil, if necessary. |
| 415 | Engine Oil Pressure Low (Shutdown) — Engine oil pressure is below 26 psig (180 kpa) for greater than 10 seconds. | External leak | Inspect the engine and surrounding area for external oil leaks; Contact your local dealer if a leak is present. |
| 421 | Engine Oil Temperature High (Warning) — The control has detected the engine oil temperature has exceeded the warning threshold. | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient. |
| 421 | Engine Oil Temperature High (Warning) — The control has detected the engine oil temperature has exceeded the warning threshold. | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable. |
| 421 | Engine Oil Temperature High (Warning) — The control has detected the engine oil temperature has exceeded the warning threshold. | Coolant level is below specification | Check coolant level; Add coolant as necessary. |
| 441 | Battery Voltage Low (Warning) — Battery voltage is low. | Loose or damaged battery cable connections | Inspect the battery cable connections; Inspect connections for corrosion; Inspect connections for loose connections. |
| 441 | Battery Voltage Low (Warning) — Battery voltage is low. | Battery charger not connected (if equipped) | Make sure that the battery charger is connected to the AC power supply; Make sure that the battery charger is connected correctly to the battery. |
| 441 | Battery Voltage Low (Warning) — Battery voltage is low. | Battery needs recharging | Using a voltmeter or multimeter, determine if the voltage is below 11 V. If so, recharge the battery. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | Coolant level is below specification | Check coolant level; Add coolant as necessary. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | Radiator blocked | Inspect for dirt, debris or obstructions; Remove blockage or winterfront as applicable. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable. |
| 488 | Intake Manifold Temperature High (Warning) — Engine intake manifold temperature has exceeded 185 °F (85 °C) for more than 90 seconds. | Fan belt is broken or loose | Inspect belt(s) for damage, wear, and proper tension; Repair or replace if damaged or worn. |
| 1438 | Fail to Crank (Shutdown) — The engine failed to crank after the generator control received a start signal. | Dead or weak battery | Verify battery voltage is at least 12 VDC (or 24 VDC if applicable); Charge or replace the battery as necessary. |
| 1438 | Fail to Crank (Shutdown) — The engine failed to crank after the generator control received a start signal. | Failed starter | Press the Reset/Fault acknowledge button on the display; Attempt to start the generator and test for B+ at the starter supply lug; If B+ is present at the starter supply lug, the starter could be defective. |
| 1472 | High AC Current (Shutdown) — The generator output current has exceeded at least 150% of rated current. | Generator set overload | Reduce the generator set load by powering off to unnecessary household appliances (examples: washer, dryer, air conditioning, etc.). |
| 5134 | Unknown Shutdown at Idle — Engine is not getting a proper fuel supply. | Fuel supply issue | Check that there is a proper supply of fuel to the engine. |
| 143 | Engine Oil Pressure Low (Warning) | Lubricating oil level is low | Check the oil level. Add oil, if necessary |
| 143 | Engine Oil Pressure Low (Warning) | External leak | Inspect the engine and surrounding area for external oil leaks; Contact your local dealer if a leak is present |
| 146 | Engine Coolant Temperature Above Normal (Warning) | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient |
| 146 | Engine Coolant Temperature Above Normal (Warning) | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 146 | Engine Coolant Temperature Above Normal (Warning) | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 146 | Engine Coolant Temperature Above Normal (Warning) | Radiator core fouled | Inspect for dirt, debris, or obstruction on core; Remove obstructions or debris, and clean the radiator core |
| 146 | Engine Coolant Temperature Above Normal (Warning) | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 146 | Engine Coolant Temperature Above Normal (Warning) | Broken fan belt | Inspect fan belt; Replace fan belt |
| 151 | Engine Coolant Temperature High (Shutdown) | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient |
| 151 | Engine Coolant Temperature High (Shutdown) | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 151 | Engine Coolant Temperature High (Shutdown) | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 151 | Engine Coolant Temperature High (Shutdown) | Radiator core fouled | Inspect for dirt, debris, or obstruction on core; Remove obstructions or debris, and clean the radiator core |
| 151 | Engine Coolant Temperature High (Shutdown) | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 151 | Engine Coolant Temperature High (Shutdown) | Broken fan belt | Inspect fan belt; Replace fan belt |
| 155 | Intake Manifold Temperature High (Shutdown) | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient |
| 155 | Intake Manifold Temperature High (Shutdown) | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 155 | Intake Manifold Temperature High (Shutdown) | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 155 | Intake Manifold Temperature High (Shutdown) | Radiator core fouled | Inspect for dirt, debris, or obstruction on core; Remove obstructions or debris, and clean the radiator core |
| 155 | Intake Manifold Temperature High (Shutdown) | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 155 | Intake Manifold Temperature High (Shutdown) | Broken fan belt | Inspect fan belt; Replace fan belt |
| 197 | Coolant Level Low (Warning) | Low coolant | Remove radiator cap and check that coolant is up to the required level |
| 415 | Engine Oil Pressure Low (Shutdown) | Lubricating oil level is low | Check the oil level. Add oil, if necessary |
| 415 | Engine Oil Pressure Low (Shutdown) | External leak | Inspect the engine and surrounding area for external oil leaks; Contact your local dealer if a leak is present |
| 421 | Engine Oil Temperature High (Warning) | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient |
| 421 | Engine Oil Temperature High (Warning) | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 421 | Engine Oil Temperature High (Warning) | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 441 | Battery Voltage Low (Warning) | Loose or damaged battery cable connections | Inspect the battery cable connections; Inspect connections for corrosion; Inspect connections for loose connections |
| 488 | Intake Manifold Temperature High (Warning) | High ambient temperature | Reduce loads or recirculation of discharge air to generator in elevated ambient |
| 488 | Intake Manifold Temperature High (Warning) | Enclosure air intake blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 488 | Intake Manifold Temperature High (Warning) | Coolant level is below specification | Check coolant level; Add coolant as necessary |
| 488 | Intake Manifold Temperature High (Warning) | Radiator core fouled | Inspect for dirt, debris, or obstruction on core; Remove obstructions or debris, and clean the radiator core |
| 488 | Intake Manifold Temperature High (Warning) | Enclosure air discharge blocked | Inspect for dirt, debris, or obstructions; Remove blockage or snow/ice buildup as applicable |
| 488 | Intake Manifold Temperature High (Warning) | Broken fan belt | Inspect fan belt; Replace fan belt |
| 1438 | Fail to Crank (Shutdown) | Dead or weak battery | Verify battery voltage is at least 12 VDC; Charge or replace the battery as necessary |
| 1472 | High AC Current (Shutdown) | Generator set overload | Reduce the generator set load by powering off to unneccessary household appliances (examples: washer, dryer, air conditioning, etc.) |
| 5134 | Unknown Shutdown at Idle | Fuel supply issue | Check that the manual shutoff valves are open |
| 5569 | Engine Combustion (Shutdown) | Intake manifold overpressurization event | Inspect the hose couplings between the compressor outlet and intake manifold; Inspect the hose couplings for damage; Inspect the clamps for damage; Inspect the turbocharger; Externally inspect the turbocharger for damage; Inspect for loose or missing bolts on the compressor housing; Inspect the mixer; Remove the air cleaner and confirm there are no loose pieces within the mixer |
| 5569 | Engine Combustion (Shutdown) | Faulty TMAP sensor | Check the intake air temperature with the GCP Display service tool or the intake manifold temperature with InPower. Confirm that the value is reasonable |
| 5569 | Engine Combustion (Shutdown) | Faulty engine harness | Inspect the engine harness and the connector pins; Disconnect the engine harness connector from the extension harness; Inspect for corroded pins, bent or broken pins, pushed back or expanded pins; Inspect for evidence of moisture in or on the connector; Inspect for missing or damaged connector seals; Inspect for dirt or debris in or on the connector pin; Disconnect harness from ECM and sensor; Measure the resistance in each pin from ECM to sensor. Resistance should be 5 ohms or less; Repair or replace harness as necessary |
| Code 143 | Engine Oil Pressure Low (Warning) | ||
| Code 146 | Engine Coolant Temperature Above Normal (Warning) | ||
| Code 151 | Engine Coolant Temperature High (Shutdown) |
| Symptom | Cause | Remedy |
|---|---|---|
| Engine Is Difficult to Start or Does Not Start | Battery voltage problem(s) | If battery voltage is low, interrupted, or open, check: Battery connections; Unswitched battery supply circuit; Fuses |
| Engine Is Difficult to Start or Does Not Start | Fuel system issue(s) | Verify that the manual fuel shutoff valve is open. |
| Engine Is Difficult to Start or Does Not Start | Air intake restriction above specification | Inspect air filter for obstruction. Replace if necessary. |
| Engine is Difficult to Start or Does Not Start | Battery voltage is low, interrupted, or open | Check the batteries connections, unswitched battery supply circuit, and fuses |
| Engine is Difficult to Start or Does Not Start | Manual fuel shutoff valve is closed | Check the manual fuel shutoff valves |
Fault codes and symptom→remedy steps extracted from this engine’s service/owner documentation; verify against the official manual before servicing.
| Item | Spec | Capacity | Part # | Interval | |
|---|---|---|---|---|---|
| Air filter | — | ||||
| Fuel filter | — | ||||
| Oil filter | — | ||||
| Battery | — | ||||
| Belt | — | ||||
| Coolant | — | ||||
| Oil | — | ||||
| Spark plug | — |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.
The Cummins/Onan C40 N6 has a displacement of 2.4 liters with 4 cylinders.
The Cummins/Onan C40 N6 powers 1 generator set(s), including Cummins/Onan RS 40.