Service parts for the GSBB
Grouped by system, with how many of each the parts manual calls for.
Oil system
1 requiredPrices captured from merchant listings; some links are affiliate links. Confirm against your serial number before ordering.
Specifications
Ratings spec sheet not in our library yet — see the documents below.
Filters & service parts
model family| Item | Spec | Capacity | Part # | Interval | |
|---|---|---|---|---|---|
| Air filter | — | 2500 hr | |||
| Fuel filter | — | ||||
| Oil filter | Change Engine Oil and Oil Filter After first 8 hours, X1 | 51243 | 1000 hr | Amazon eBay $10.00 | |
| Battery | — | 1000 hr | |||
| Belt | — | ||||
| Coolant | — | ||||
| Oil | 0W-40 Synthetic Engine Oil | 80.0 oz | — | 8 hr | |
| Spark plug | — | 16800 hr |
Compiled from this model's family documentation — may include parts for closely-related variants. Confirm the exact part for your serial number.
Service intervals
8| Item | Action | Hours | Months | Notes |
|---|---|---|---|---|
| Engine Oil and Oil Filter | Change | 8 hr | First service — After first 8 hours | |
| Engine Oil Level | Check | 24 hr | Daily or every 24 hours; check daily during power outages, or monthly without power outages | |
| Engine Valve Clearance | Adjust | 50 hr | First service — After first 50 hours; must be performed by a qualified mechanic (authorized Cummins Onan dealer) | |
| Starting Battery | Clean | 100 hr | 3 mo | Clean and check starting battery |
| Engine Cooling Fins | Clean | 250 hr | Perform sooner if engine performance deteriorates | |
| Spark Plugs and Wires | Replace | 250 hr | Perform sooner if engine performance deteriorates | |
| Complete System Test | Test | 400 hr | See automatic transfer switch manual for testing of load transfer | |
| Engine Air Filter | Replace | 400 hr |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Service specifications
6| Type | Item | Value | Unit | Condition |
|---|---|---|---|---|
| Gap | Spark Plug Gap | .020 | inch | .51 mm |
| Pressure | Fuel Pressure (all loads), 60 Hz Spec A/Canadian Spec B | 7-11 (Propane Vapor) / 5-11 (Natural Gas) | inches WC | measured at genset fuel regulator service port |
| Pressure | Fuel Pressure (all loads), US Spec B/Canadian GSBC Spec B | 12-14 (Propane Vapor) / 5-7 (Natural Gas) | inches WC | measured at genset fuel regulator service port |
| Torque | Spark Plug Torque | 15 | ft-lb | 20 N-m |
| Valve clearance | Intake and Exhaust Cold Valve Lash | 0.004-0.006 | inch | 0.10-0.15 mm; measured at 0.25 in (6.35mm) past top dead center |
| Voltage | Output Voltage Adjustment Range | 240 ± 7% (17 VAC) | VAC |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Recommended fluids
| Fluid | Grade | Standard | Ambient | Capacity | Notes |
|---|---|---|---|---|---|
| Engine oil | 5W-30 Synthetic | 2.3 Liters | Approximately 80 oz (2.3 Liters); refill with 67 oz (2 liters) when changing oil and filter |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Fault codes
20| Code | Name | Meaning | Severity | Action |
|---|---|---|---|---|
| 12 | Overvoltage | Generator set loads, wire connections, windings | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 13 | Undervoltage | Generator set loads, wire connections, windings | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 14 | Overfrequency | Generator set loads, engine governor function, fuel supply, air fuel mixture, exhaust system, choke, demand regulator, carburetor, generator windings, wire connections | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 15 | Underfrequency | Generator set loads, engine governor function, fuel supply, air fuel mixture, exhaust system, choke, demand regulator, carburetor, generator windings, ignition, wire connections | Shutdown | Reduce the number of connected loads especially loads that require higher starting current such as air conditioners; have unit serviced by an authorized Cummins Onan dealer |
| 19 | Governor Actuator shutdown | Wire connections, governor actuator | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 2 | Low Oil Pressure Fault | Oil Level too low/high, faulty switch, faulty oil pressure relief valve, faulty oil pump | Shutdown | Check oil level: add or drain oil as necessary |
| 22 | Governor Actuator Overload | Generator set loads, wire connections, fuel supply, air fuel mixture, exhaust system, governor actuator, ignition system | Shutdown | Reduce the number of connected loads especially loads that require higher starting current; check and service air filter as necessary; have unit serviced by an authorized Cummins Onan dealer |
| 27 | Voltage Sense Lost | Generator set loads, generator windings, ignition, wire connections | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 29 | High Battery Voltage | Incorrect battery configuration, wire damage, faulty charger, control | Shutdown | Have battery charger serviced by an authorized Cummins Onan dealer |
| 32 | Low Cranking Speed Sense | Starter, engine components, air intake system, exhaust system, generator windings, wire connections, battery, battery connections, oil viscosity | Shutdown | Clean and tighten battery cable connections; recharge or replace battery; verify engine oil viscosity is correct for ambient temperature; have unit serviced by an authorized Cummins Onan dealer |
| 35 | Control Card Failure | Faulty program | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 36 | Generator Set Stopped Without Fault Condition | Fuel supply, air fuel mixture, exhaust system, choke demand regulator, carburetor, generator windings, ignition, wire connections | Shutdown | Check the fuel source; open any closed fuel valves; secure spark plug leads to spark plugs; check and service air filter; replace spark plugs; check for mechanical damage |
| 37 | Invalid Set Configuration | Generator set configuration, control | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 4 | Overcrank | Faulty switch, faulty external start command, fuel supply, air fuel mixture, exhaust system, wire connections, starter, ignition system | Shutdown | Open any closed fuel valves; secure spark plug leads to spark plugs; check and service air filter as necessary; replace spark plugs |
| 43 | Processor Fault | Faulty program | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 45 | Speed Sense Fault | Loads, generator windings, wire connections | Shutdown | Have unit serviced by an authorized Cummins Onan dealer |
| 46 | Generator Set Overload | Loads, wire connections, windings | Shutdown | Reduce the number of connected loads; check and service air filter as necessary; have unit serviced by an authorized Cummins Onan dealer |
| 76 | Alternator Over Temp | Wire connections, faulty temperature sensor, faulty DC fan, blocked intake or exhaust openings | Shutdown | Verify the generator set enclosure for clear intake and exhaust openings; have unit serviced by an authorized Cummins Onan dealer |
| 78 | Low Fuel Pressure | Wire connections, fuel system, fuel pressure switch | Shutdown | Open any closed fuel valves; have unit serviced by an authorized Cummins Onan dealer |
| 79 | Failure To Transfer To Generator Set | Wire connections, faulty positional switch, faulty transfer switch component(s) | Shutdown | Verify that the main AC circuit breaker on the generator set is to On; have unit serviced by an authorized Cummins Onan dealer |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Procedures
3To Adjust the Output Voltage adjustment
Tools: AC volt meter
- Connect an accurate AC volt meter across L1 and L2 while the generator set is running
- With Output Volts selected on the Adjustments Menu screen, press the up or down arrow button to adjust the voltage
- The control allows an adjustment of 240 VAC ± 7% (17 VAC)
- Press the BACK button to save the settings and return to the home screen
Changing Engine Oil and Oil Filter maintenance
⚠ Used engine oil can cause cancer or reproductive toxicity; avoid skin contact and breathing of vapors
- Run the generator set until warm, shut down and place pan under end of oil drain hose
- Make sure oil drain hose is connected to drain valve; open drain valve; reclose when oil stops draining
- Spin off the oil filter canister and clean the filter mounting surface; remove old gasket if it remains
- Apply thin film of clean oil to new filter gasket; spin new filter on until gasket touches block, then turn additional 1/2 to 3/4 turn
- Refill with 67 oz (2 liters) of oil
- Start and run for 30 seconds
- Shut engine off and wait 5 minutes
- Add more oil slowly to bring oil level to the FULL mark on dipstick
- Dispose of used oil and oil filter according to local environmental regulations
Replacing the Air Filter Element maintenance
⚠ Disconnect negative battery cable before working on the generator set to prevent starting
- Move Switch (S2) to Stop position, disconnect remote harness (P7), remove negative battery cable to prevent starting
- Remove the outer and inner cover and reassemble with a new air filter element
- Make sure the outer cover is seated before tightening its wing nut
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Common questions
What oil filter fits the Cummins/Onan GSBB?
The Cummins/Onan GSBB uses oil filter part number 51243.
Troubleshooting
6Fault codes
| Code | Meaning |
|---|---|
| 2 | Low Oil Pressure Fault |
| 3 | Service Check Fault |
| 4 | Overcrank |
| 12 | Overvoltage |
| 13 | Undervoltage |
| 14 | Overfrequency |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing. Full Cummins/Onan GSBB troubleshooting guide (21 entries) →
Parts
6model family| Part # | Description | Qty | System | |
|---|---|---|---|---|
| 20GSBB-6714A | Heater Assembly (Spec A and Canadian GSBB Spec B) | 1 | Heater | Amazon eBay |
| 20GSBB-6714B | Heater Assembly (US GSBB Spec B and Canadian GSBC Spec B) | 1 | Heater | Amazon eBay |
| 20GSBC-6727B | Heater Assembly (US GSBB Spec B and Canadian GSBC Spec B) | 1 | Heater | Amazon eBay |
| A029V089 | 1 | Operator manual | Amazon eBay | |
| A030B021 | Harness, Heater (Alternator Heater) (Spec A and Canadian GSBB Spec B) | 1 | Harness | Amazon eBay |
| A041U952 | Harness, Interface (US GSBB Spec B and Canadian GSBC Spec B) | 1 | Harness | Amazon eBay |
Compiled from this model's family documentation — may include parts for closely-related variants. Confirm the exact part for your serial number. See the full parts catalog to search and cross-reference.
Available documents
Operator's manual (Cummins/Onan)Reference (Cummins/Onan)Service manual — A029V088 Cummins-Onan GSBB spec A Installation Manual (04-2910) (Cummins/Onan)Service manual — A030A239 Cummins-Onan GSBB (spec A-B) GSBC (spec B) Standby Genset Service manual (09-2013) (Cummins/Onan)