PACCAR PX-9 CM2350 (2013-17) Fault Code:272 PID:SID 126 SPN:1347 FMI:3 Engine Fuel Pump Pressurizing Assembly 1 Circuit – Voltage Above Normal or Shorted to High Source

Reason:
Engine Fuel Pump Pressurizing Assembly 1 Circuit – Voltage Above Normal or Shorted to High Source. High signal voltage or open circuit is detected at the fuel pump actuator circuit.

Effect:
Engine may run rough, may stop running, may not start, or may be difficult to start.

Circuit Description:
The circuit is a pulse-width modulation (PWM) driver in the engine control module (ECM) that controls the fuel pump actuator. The actuator is grounded in the ECM. The actuator is normally open. The PWM duty cycle to the fuel pump actuator depends on the difference between desired rail pressure and sensed rail pressure.

Component Location:
The high-pressure fuel pump is mounted to the gear housing. The fuel pump actuator is mounted on the fuel pump. The fuel pressure sensor is mounted in the high pressure fuel rail. The fuel pressure relief valve is mounted on the high pressure fuel rail.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected a short to battery, short pin-to-pin, or open circuit in the fuel pump actuator circuit

Action Taken When the Fault Code is Active:
1) The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2) Sensed fuel rail pressure will not follow the commanded rail pressure.
3) Exhaust Gas Recirculation (EGR) valve operation will be disabled.
4) Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.

Conditions for Clearing the Fault Code:
1) To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
5) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
This fault becomes active when the ECM detects an open or short circuit in the fuel pump actuator circuit. Causes of this fault code include a short circuit to a positive voltage, open circuit, short circuit to ground, or low resistance (fuel pump actuator is shorted internally) in the fuel pump actuator circuit. If there is high harness resistance or an intermittent open circuit,

Fault Code 2311 can have high inactive counts. When excessive current or a short circuit is detected, the ECM driver to the fuel pump actuator is turned off to protect the circuit. It is necessary to cycle the keyswitch OFF and then back ON before the ECM will run this diagnostic again. The ECM driver is enabled at key ON, so if the cause is no longer present, the fault code will become inactive and can be cleared. If the fault code is intermittent, inspect the ECM connector, wiring harness, and harness connectors for loose pins and bad connections. Look closely for loose wire connections that can cause an intermittent short to ground or open circuit in the wiring harness or connectors. It may help to wiggle the harness and harness connections and watch for fault code state changes.

Possible Causes:
1) Inactive fault codes
2) Damaged engine harness
3) Faulty circuit response
4) Faulty ECM