SPN 654 monitors the operational status and command output of the fuel injector assigned to cylinder number four on the engine’s primary fuel system. This parameter is broadcast by the Engine Control Module (ECM) and reflects both the commanded injection events and any detected fault conditions associated with the cylinder 4 injector circuit. It is widely used across heavy-duty diesel platforms including Cummins ISX, ISB, and ISC engines, Detroit Diesel DD13 and DD15 Series, PACCAR MX-13, Volvo D13, and Caterpillar C13 and C15 powerplants. In off-highway equipment, this SPN appears in John Deere PowerTech and Caterpillar ACERT engine families used in excavators, graders, and agricultural machinery. The parameter is critical because a malfunctioning cylinder 4 injector directly degrades combustion efficiency, elevates exhaust emissions, increases thermal loading on adjacent components, and can cause severe mechanical damage if raw fuel washes cylinder walls or hydraulic lock occurs in extreme cases.
Technical Overview
Modern common-rail and unit injector systems use solenoid-driven or piezoelectric injectors that receive precisely timed electrical pulses from the ECM. For cylinder 4, the ECM outputs a high-side or low-side driver signal — typically a pulse-width modulated (PWM) current waveform — to energize the injector solenoid or piezo stack. In solenoid injectors such as those used in Cummins XPI and Bosch CRIN systems, the ECM delivers a peak-and-hold current profile: an initial peak of approximately 18–20 amperes to open the needle valve rapidly, followed by a hold current of 8–12 amperes to maintain the valve position. Piezoelectric injectors, used extensively in Bosch CRS3 systems and Delphi DP systems found on MAN and Mercedes-Benz engines, operate on a capacitive charge-and-discharge principle at voltages between 100 and 200 VDC internally managed by the injector driver module. The ECM continuously monitors injector circuit continuity, coil resistance (typically 0.4–2.0 ohms for solenoid types), return current waveform shape, and actual versus commanded injection quantity through cylinder balance feedback derived from crankshaft acceleration data. SPN 654 reflects the status of this entire subsystem for cylinder 4 specifically, including open-circuit, short-to-ground, short-to-battery, and overcurrent conditions detected by the driver stage.
J1939 Network Behavior
SPN 654 is transmitted within the Electronic Engine Controller #1 (EEC1) and Engine Configuration message structures, though its fault data most commonly appears within Diagnostic Message 1 (DM1) and DM2 frames broadcast by the engine ECM as the source node. The associated PGN for active diagnostic trouble codes is PGN 65226 (0xFECA) for DM1 active faults, transmitted at a default rate of 1 Hz when a fault is active, or on-request via PGN 59904 for DM2 previously active faults. The engine ECM — identified by source address 0x00 in standard configurations — owns and broadcasts this data. Other controllers on the network, such as the Aftertreatment Control Module (ACM), Transmission ECU, and Vehicle Management Computer (VMC), subscribe to this information to execute coordinated derate strategies, inhibit regeneration cycles when combustion quality is compromised, and log fleet telematics data. In Volvo and Mack applications using the VECU/EECU architecture, SPN 654 fault data also triggers coordinated responses in the body builder interface modules. Technicians using Cummins INSITE, Detroit Diesel DiagnosticLink, or Caterpillar ET will see this SPN reported with associated Failure Mode Identifiers (FMIs) that define the specific circuit condition detected.
Diagnostic Importance
A fault on the cylinder 4 injector circuit triggers immediate ECM protection responses that vary by manufacturer and calibration severity. In most Cummins engines, an active injector fault initiates a cylinder cut-out strategy, effectively disabling fuel delivery to cylinder 4 to prevent raw fuel accumulation in the exhaust and potential aftertreatment damage — particularly to the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF), which can experience thermal runaway from unburned hydrocarbon oxidation. Detroit Diesel DD-series engines similarly enter a reduced power mode, limiting torque output by 30–50% depending on the specific FMI severity. Caterpillar ACERT engines may trigger engine protection shutdown sequences if balance cylinder data indicates combustion is absent for more than a defined number of engine cycles. Ignoring an active SPN 654 fault code risks progressive crankshaft bearing wear from lubrication dilution caused by fuel blow-by past the cylinder 4 rings, catalytic converter substrate meltdown, and in severe cases, hydrostatic lock if a stuck-open injector floods the combustion chamber during an overnight soak. Emission compliance is also immediately affected, as OBD-HD mandates require continuous monitoring of injector function for in-use surveillance.
Common Failure Patterns
Field experience across Cummins dealer networks and Detroit Diesel service centers reveals several recurring failure modes. Wiring harness chafing at the valve cover pass-through grommet is among the most frequent causes, particularly on ISX15 and ISX12 engines where the injector harness routes along the top of the head and contacts the rocker housing over time. This produces intermittent open-circuit or short-to-ground FMIs (FMI 5 or FMI 6) that are difficult to reproduce at ambient temperature but consistent after thermal soak. Connector corrosion at the cylinder 4 injector Metri-Pack or Deutsch connector is common in high-wash environments like vocational trucks operating in construction or mining. Injector coil failure — where the solenoid winding develops increased resistance or an open — presents as FMI 5 (current below normal) and is confirmed by measuring coil resistance out-of-circuit at the injector body terminals. Carbon fouling of the injector tip causes erratic injection quantity deviations detected through cylinder balance monitoring, generating FMI 7 or FMI 14 codes even with a fully intact electrical circuit. On high-mileage PACCAR MX-13 engines, internal injector wear causing return fuel quantity to exceed specification is a documented failure mode that triggers balance fault codes specifically for cylinder 4 when that injector has accumulated the most wear from its position in the firing order.
Diagnostic Approach
Begin diagnosis by retrieving all active and inactive fault codes with FMI notation using OEM-level software — Cummins INSITE, DiagnosticLink 8.x, Caterpillar ET, or Volvo VCADS. Document the FMI to direct circuit or mechanical investigation. For electrical faults (FMI 3, 4, 5, 6), perform a harness resistance check from the ECM connector pin for cylinder 4 driver output to the injector connector with the harness disconnected at both ends to isolate the circuit. Reference values for solenoid resistance are typically 0.5–1.2 ohms at 20°C for Cummins XPI injectors and 0.4–0.8 ohms for Detroit Diesel CRI2 units. Perform an insulation resistance test at 500 VDC between the injector circuit and chassis ground — values below 1 MΩ indicate harness insulation degradation. For suspected mechanical or calibration issues, use the injector cut-out test available in INSITE or VCADS to disable cylinder 4 and observe RPM drop; a minimal RPM change confirms the injector was already contributing little to power output. Follow with an injector return flow test using calibrated graduated cylinders to quantify leak-off volume against OEM specification. If electrical circuits and return flow are within spec but cylinder balance faults persist, escalate to injector replacement and re-zero the IQA (Injector Quantity Adjustment) codes in the ECM using the replacement injector’s trim code, a mandatory step on Bosch CRI-equipped engines including MAN TGX and Mercedes-Benz OM471 platforms to restore accurate fuel mapping for cylinder 4.
Fault Codes for SPN 654FMI 0: Data valid but above normal operational range (most severe)
SPN 654 FMI 0 indicates cylinder 4 fuel injector flow rate exceeds normal operational parameters, triggering ECM safety protocols. This fault commonly appears after contaminated fuel events or following injector replacement when calibration values weren’t properly updated. The ECM detects abnormally
View SPN 654 FMI 0 Diagnostic Guide →
FMI 1: Data valid but below normal operational range (most severe)
This fault indicates the ECM detected the electrical current for cylinder 4 injector is below the normal operational threshold, often due to a short-to-ground or open circuit. Technicians commonly encounter this after replacing the ECM without reprogramming injector calibration codes, or after a wir
View SPN 654 FMI 1 Diagnostic Guide →
FMI 2: Data erratic, intermittent or incorrect
SPN 654 FMI 2 indicates erratic data from the fuel injector of cylinder 4. This fault often appears after a recent ECM update or wiring harness replacement. It commonly manifests in inconsistent engine performance, particularly noticeable during cold starts or under load. Technicians may encounter t
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FMI 3: Voltage above normal or shorted high
SPN 654 FMI 3 indicates voltage above normal threshold on cylinder 4 fuel injector circuit, typically exceeding 5.5V on low-side driver monitoring. This fault commonly appears after engine bay wash procedures or during wet weather conditions when moisture infiltrates connector seals. The ECM detects
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FMI 4: Voltage below normal or shorted low
SPN 654 FMI 4 indicates the ECM detected voltage below normal or a short-to-ground on the Cylinder 4 fuel injector circuit. This fault commonly appears after a technician replaces the ECM without performing an injector solenoid resistance check, or when a chafed harness contacts the engine block nea
View SPN 654 FMI 4 Diagnostic Guide →
FMI 5: Current below normal or open circuit
SPN 654 FMI 5 indicates an open circuit or below-normal current in the fuel injector for cylinder 4. This fault is often detected after a technician replaces an ECM or when wiring harnesses are disturbed during maintenance. Typically, engines experience misfires, reduced performance, or even failure
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FMI 6: Current above normal or grounded circuit
Fault code SPN 654 FMI 6 signals an overcurrent condition or grounding in the fuel injector circuit of cylinder 4. This issue often occurs after injector replacements or electrical harness modifications. Technicians typically observe this fault when erroneous signals trigger the engine control modul
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FMI 7: Mechanical system not responding properly
SPN 654 FMI 7 indicates the Engine Control Module (ECM) has detected that the fuel injector for cylinder 4 is not responding properly to the commanded actuation signal. This mechanical system fault typically arises when the injector needle sticks, the solenoid armature fails to lift, or the internal
View SPN 654 FMI 7 Diagnostic Guide →
FMI 9: Abnormal update rate
SPN 654 FMI 9 indicates the ECM detects inconsistent communication timing with cylinder 4 fuel injector. This abnormal update rate typically manifests during high-load operations when injector response timing falls outside manufacturer specifications. Technicians commonly encounter this fault after
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FMI 11: Root cause not known
SPN 654 FMI 11 indicates the ECM has detected an anomaly on the fuel injector circuit for cylinder 4 but cannot determine the specific failure mode. This code often appears after a forced DPF regeneration or an ECM software update when injector trim values are reset. Technicians may find it alongsid
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FMI 12: Bad intelligent device or component
SPN 654 FMI 12 is a critical diagnostic code indicating a malfunction in the fuel injector for cylinder 4. This fault is frequently observed after a forced DPF regeneration, which can sometimes stress the injector system. It also appears commonly following ECM replacements where calibration is not p
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FMI 13: Out of calibration
SPN 654 FMI 13 indicates cylinder 4 fuel injector calibration drift beyond ECM tolerance parameters. This fault commonly appears after ECM software updates or injector replacement procedures where adaptation values weren’t properly reset. The injector’s actual fuel delivery deviates from commanded p
View SPN 654 FMI 13 Diagnostic Guide →
FMI 14: Special instructions
SPN 654 FMI 14 indicates the Engine Control Module has issued a special instruction regarding the Cylinder 4 fuel injector circuit, often triggered after a forced DPF regeneration or injector replacement without proper ECM recalibration. Technicians frequently encounter this fault when the ECM detec
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FMI 18: Data valid but below normal operating range (moderately severe)
SPN 654 FMI 18 pertains to the engine fuel injector for cylinder 4, where data is valid but below the normal operating range. This fault often arises after ECM updates or injector replacements, particularly if calibration is incomplete. Technicians frequently encounter this issue during routine main
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FMI 31: Condition exists
SPN 654 FMI 31 indicates a persistent condition exists with the cylinder 4 fuel injector that doesn’t fit standard failure categories. This fault commonly appears during routine injector performance testing or when ECM detects anomalous fuel delivery patterns that fall outside normal operating param