Cummins ISB4.5 CM2150 Fault Code: 323 PID: SID 6 SPN: 656 FMI: 5 Injector Solenoid Driver Cylinder 5 Circuit – Current Below Normal or Open Circuit.

Circuit Description
The injector solenoid valves control fueling quantity and injection timing. The electronic control module (ECM) energizes the solenoid by closing a high-side and a low-side switch. There are two high-side switches and six low-side switches inside the ECM. The injectors for cylinders 1 and 2 (front bank) share a single high-side switch that connects the injector circuit to the source of high voltage inside the ECM. Likewise, the injectors for cylinders 3 and 4 (rear bank) also share a single high-side switch. Each injector circuit has a dedicated low-side switch that completes the circuit path to ground inside the ECM.

Component Location
The engine harness connects the ECM to three injector circuit pass-through connectors that are located in the rocker housing. Internal injector harnesses are located under the valve cover and connect the injectors to the engine harness at the pass-through connectors. Each housing pass-through connector provides power and return for two injectors.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the engine is operating.

Conditions for Setting the Fault Codes
The ECM senses current as each injector is actuated. If the ECM detects a persistent circuit error on an injector circuit, this fault code will become active. If a circuit error is determined to cause excessive current, the ECM will disable the injector event for the cylinder(s) that is malfunctioning.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
-The injector will be disabled for the malfunctioning cylinder.

Conditions for Clearing the Fault Code
-The ECM will attempt to enable any disabled injector circuit whenever the engine is started and approximately once per minute while the engine is running. If an injector circuit fault is active and the faulty condition is repaired, the fault will become inactive once the engine is restarted or if the engine is permitted to idle for more than a minute.
-The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
-The ECM will turn off the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
-This fault code and MIL can also be cleared with INSITE™ electronic service tool.

Shop Talk
If more than one injector fault code is occurring and the faults occur for injector circuits in the same bank, a short circuit exists.

If a fault condition is intermittent and especially if more than one injector fault code is occurring, look for a wire harness that can short to components inside the rocker housing or a short circuit to ground in the injector solenoid. When looking for short circuits in the injector harnesses, pay particular attention to the wire insulation, making sure there are no shorts to a rocker lever. An intermittent short can result if the wiring harness insulation rubs through near a rocker lever. An intermittent short can cause a single injector fault code.

If the fault(s) occur intermittently, the engine can exhibit a misfire even if the injector circuit fault code does not always register. If a single cylinder exhibits misfires, look for an open circuit problem. If several cylinders on the same bank exhibit misfires, look for a short circuit anywhere in the bank of cylinders.

Causes of a single injector fault are:

– Open circuit in the engine harness(es) or injector solenoid
– High resistance in a single injector or injector solenoid
– Extremely low resistance in an injector solenoid (injector shorted internally but not to ground)
– Malfunctioning or damaged ECM.

Causes of multiple injector fault codes in the same bank of injectors are:

-Short circuit in the engine harness(es) – either shorts to ground or to other wires in the engine harness
-Short circuit in any of the three injectors in the bank – shorts to ground
-Malfunctioning or damaged ECM.