Complete reference guide to the most common Kenworth diagnostic trouble codes with proven repair solutions. Ensure DOT compliance and minimize fleet downtime with expert-verified fixes.
DOT-compliant repair procedures with complete documentation for audit trails.
Critical engine codes requiring immediate attention for compliance and safety
| Code | Description | Common Causes | Fix Procedure |
|---|---|---|---|
| SPN 100 FMI 1 | Engine Oil Pressure Low | Low oil level, worn pump, clogged filter | Check oil level, replace filter, test pressure sensor. Critical - Stop Engine |
| SPN 110 FMI 0 | Coolant Temperature High | Low coolant, thermostat stuck, fan failure | Check coolant level, test thermostat, verify fan operation |
| SPN 102 FMI 3 | Intake Manifold Pressure Sensor | Sensor failure, wiring issue, boost leak | Test sensor voltage, check connections, inspect for boost leaks |
| SPN 94 FMI 1 | Fuel Pressure Low | Clogged fuel filter, weak pump, air in system | Replace fuel filter, prime system, test lift pump pressure |
| SPN 190 FMI 0 | Engine Speed High | Governor malfunction, throttle stuck | Check throttle linkage, calibrate governor, verify ECM parameters |
| SPN 105 FMI 0 | Intake Air Temperature High | CAC leak, high ambient temp, sensor drift | Inspect charge air cooler, verify sensor reading, check intercooler |
| SPN 164 FMI 2 | Injection Control Pressure | ICP sensor, wiring, high pressure pump | Test ICP sensor, check pump output, verify oil quality |
| SPN 174 FMI 0 | Fuel Temperature High | Return fuel restriction, cooler blocked | Check fuel cooler flow, verify return line restriction |
| SPN 157 FMI 3 | Fuel Rail Pressure Sensor | Sensor failure, connector corrosion | Test sensor output, clean connections, replace if faulty |
| SPN 108 FMI 3 | Barometric Pressure Sensor | Sensor failure, ECM internal fault | Replace sensor, check ECM ground, update calibration |
| SPN 651 FMI 5 | Injector Cylinder #1 | Injector failure, wiring open circuit | Test injector resistance, check harness continuity |
| SPN 91 FMI 1 | Accelerator Pedal Position | Pedal sensor, wiring, calibration | Calibrate pedal, test sensor voltages, check connectors |
| SPN 1127 FMI 0 | Turbocharger Speed High | Boost leak, wastegate stuck, VGT failure | Check boost system, test VGT actuator, inspect wastegate |
| SPN 411 FMI 2 | EGR Differential Pressure | EGR valve stuck, sensor clogged | Clean EGR valve, replace differential pressure sensor |
| SPN 2659 FMI 0 | EGR Temperature High | EGR cooler failure, excessive EGR flow | Test EGR cooler efficiency, check EGR valve operation |
EPA-mandated codes requiring documented repairs for compliance. See our DPF/SCR playbook for detailed procedures.
| Code | Description | Common Causes | Compliance Fix |
|---|---|---|---|
| SPN 3361 FMI 1 | DEF Quality Poor | Contaminated DEF, wrong fluid type | Drain/flush DEF tank, refill with certified DEF. Document for EPA |
| SPN 3363 FMI 0 | DEF Tank Level Critical | Empty tank, sensor failure | Refill DEF, test level sensor. Inducement warning |
| SPN 3226 FMI 2 | NOx Sensor Outlet | Sensor failure, wiring issue | Replace NOx sensor, verify SCR efficiency. EPA reportable |
| SPN 3251 FMI 0 | DPF Soot Load Critical | Excessive idling, incomplete regens | Force stationary regen, check for upstream issues |
| SPN 3719 FMI 15 | DPF Ash Load High | Normal accumulation over time | Schedule DPF cleaning service, document mileage |
| SPN 3720 FMI 15 | DPF Regen Required | Normal soot accumulation | Perform parked regeneration, log completion |
| SPN 4334 FMI 1 | DEF Pump Pressure Low | Pump failure, line restriction | Test pump output, check for frozen lines |
| SPN 4364 FMI 18 | SCR Conversion Low | Catalyst degradation, dosing issue | Test SCR efficiency, check DEF dosing rate |
| SPN 3031 FMI 9 | DEF Dosing Unit | Doser valve stuck, crystallization | Clean/replace doser valve, check for DEF quality |
| SPN 3246 FMI 0 | DPF Outlet Temperature High | Active regen in progress, excessive soot | Monitor regen completion, check for oil consumption |
| SPN 3216 FMI 2 | NOx Sensor Inlet | Sensor failure, contamination | Replace inlet NOx sensor, verify EGR operation |
| SPN 1761 FMI 17 | DEF Tank Temperature | Heater failure, sensor issue | Test tank heater operation, check sensor resistance |
| SPN 5246 FMI 0 | SCR Inducement Level 1 | Multiple aftertreatment faults | Address all active faults, document repairs for DOT |
| SPN 3597 FMI 3 | DEF Pressure Sensor | Sensor failure, wiring issue | Replace pressure sensor, verify harness integrity |
| SPN 3610 FMI 2 | DEF Header Pressure | Restriction in DEF lines | Check for crystallization, replace DEF filter |
Communication and electrical system codes affecting multiple modules. Review CAN bus troubleshooting for complex issues.
| Code | Description | Common Causes | Fix Procedure |
|---|---|---|---|
| SPN 639 FMI 2 | J1939 Network #1 | CAN bus failure, terminator issue | Check terminators (120Ω), verify bus voltage |
| SPN 625 FMI 9 | CAN Data Link | Module offline, wiring damage | Test CAN resistance, check for shorted wires |
| SPN 168 FMI 0 | Battery Voltage High | Alternator overcharge, regulator failure | Test charging voltage, replace alternator/regulator |
| SPN 168 FMI 1 | Battery Voltage Low | Battery failure, alternator issue | Load test batteries, verify alternator output |
| SPN 629 FMI 12 | ECU Internal Failure | ECM hardware fault | Attempt ECM reset, replace if persistent |
| SPN 520210 FMI 3 | Body Controller Voltage | BCM power supply issue | Check BCM power/ground, test supply voltage |
| SPN 524287 FMI 9 | Transmission CAN Timeout | TCM communication lost | Check TCM power, verify CAN connection |
| SPN 84 FMI 2 | Vehicle Speed Sensor | Sensor failure, tone ring damage | Test VSS output, inspect tone ring condition |
| SPN 1069 FMI 2 | ABS Module Communication | ABS ECU failure, connector issue | Check ABS module connections, scan for sub-codes |
| SPN 524288 FMI 3 | Instrument Cluster Comm | Cluster failure, CAN issue | Verify cluster power, check data link |
| SPN 523 FMI 7 | Transmission Range | Gear selector issue, wiring | Calibrate range sensor, check shift linkage |
| SPN 97 FMI 3 | Water in Fuel Indicator | Water detected, sensor fault | Drain water separator, test WIF sensor |
| SPN 1636 FMI 2 | Intake Air Heater | Relay failure, element open | Test grid heater relay, check element resistance |
| SPN 677 FMI 3 | Starter Relay | Relay stuck, wiring issue | Test relay operation, verify control circuit |
| SPN 970 FMI 31 | Engine Brake | Jake brake solenoid, wiring | Test solenoid resistance, check brake operation |
| SPN 524289 FMI 5 | Headlight Circuit Open | Bulb failure, relay issue | Test headlight relay, check bulb and wiring |
| SPN 27 FMI 7 | VGT Actuator | Actuator stuck, calibration | Perform VGT learn procedure, test actuator travel |
| SPN 132 FMI 3 | Mass Air Flow Sensor | MAF contamination, failure | Clean MAF sensor, verify air filter condition |
| SPN 173 FMI 3 | Exhaust Temperature Sensor | Sensor failure, wiring damage | Test sensor resistance, check connector condition |
| SPN 1176 FMI 3 | Turbo Inlet Temperature | Sensor drift, exhaust leak | Verify sensor reading, check for exhaust leaks |
Proper documentation of DTC repairs is essential for DOT compliance and audit readiness. Learn about datalogger setup for automatic documentation.
The following code categories require special documentation for EPA compliance audits:
Any codes indicating DEF system tampering or SCR bypass must be reported and resolved within 30 days.
SPN 5246 series codes triggering derate must be documented with repair timeline.
Codes indicating NOx levels above thresholds require immediate action and documentation.
Answers to compliance and repair questions about Kenworth diagnostic codes
Safety-critical codes affecting brakes (ABS/ESC), emissions codes causing derate, and any codes illuminating the red stop engine light must be addressed immediately. EPA-mandated aftertreatment codes have specific timelines - DEF quality issues must be resolved within 200 miles, while NOx sensor failures allow up to 200 hours of operation. Document all repairs for DOT audits. Reference our critical codes guide for complete compliance requirements.
DOT requires maintenance records be kept for 1 year minimum, but EPA aftertreatment repairs should be kept for the vehicle's useful life (435,000 miles or 10 years for heavy-duty). Electronic records through a datalogger system are preferred. Keep records of: initial fault codes, diagnostic procedures performed, parts replaced, labor hours, verification testing, and clearance documentation. This protects against compliance violations and warranty disputes.
Yes, but document the decision and monitor closely. Non-critical codes that don't affect safety or emissions compliance can be scheduled for next PM service. However, multiple non-critical codes may indicate developing issues. Set up monitoring through live alerts to track if they worsen. During DOT inspections, be prepared to show you're aware of the codes and have scheduled repairs.
Recurring codes indicate either an incorrect diagnosis, faulty replacement part, or underlying issue not addressed. Document each repair attempt for compliance. Check for related codes that might reveal root cause - use our guide on understanding code relationships. Consider intermittent wiring issues or software updates. If aftertreatment codes recur, verify DEF quality and review driving patterns that might prevent proper regeneration.
No, Kenworth uses J1939 SPN/FMI codes which provide more detail than generic OBD-II codes. While some overlap exists, Kenworth-specific codes (especially 524xxx series) won't appear on generic scanners. For complete diagnostics, use Kenworth ServiceLink or PACCAR Davie4. Generic tools miss proprietary body controller and some aftertreatment codes critical for compliance. Compare with other PACCAR trucks like Peterbilt's system for cross-reference.
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