CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – 209-001   System Description

Table of Contents

General Information
ECM Inputs

General Information


This ISX CM871 and ISM CM876 engine control systems are electronically operated fuel control systems that also provide many operator and vehicle features.

The base functions of the control system include fueling and timing control, limiting the engine speed operating range between the low and high idle set points and reducing exhaust emissions while optimizing engine performance. The system also controls the engine brakes and the aftertreatment system.

The control system uses inputs from the operator and sensors to determine the fueling and timing required to operate at the desired engine speed and at the required emissions level.

ECM Inputs

The electronic control module (ECM) is the control center of the system. It processes all of the inputs and sends commands to the fuel system, vehicle and engine control devices.

The ECM performs diagnostic tests on most of the circuits and will activate a fault code if a problem is detected in one of these circuits. Along with the fault code identifying the problem, a snapshot of the engine operating parameters at the time of the fault code activation is also stored in the ECM memory.

Active fault codes will cause a diagnostic lamp to activate to signal the driver a fault code has been activated.

The ECM can communicate with electronic service tools and some other vehicle controllers (such as transmissions, ABS, ASR, electronic dash displays and so on) through the SAE J1939 datalink or the SAE J1708 datalink.

Some vehicles and equipment will have SAE J1939 networks on them that link many of the “smart” controllers together. Vehicle control devices can temporarily command engine speed or torque to perform one of its functions (that is, transmission shifting, anti-lock braking and so on).

The control system utilizes a number of sensors to provide information about the engine operating parameters. These sensors include:

  • Engine coolant temperature sensor
  • Intake manifold air temperature/pressure sensor
  • Engine oil pressure sensor
  • Engine oil temperature sensor
  • Engine speed sensor
  • Camshaft position sensor
  • Barometric pressure sensor
  • Rail fuel pressure sensor
  • Water-in-fuel sensor
  • Exhaust gas recirculation (EGR) temperature sensor
  • Exhaust gas pressure sensor
  • EGR differential pressure sensor
  • Turbocharger speed sensor
  • Turbocharger compressor inlet air temperature sensor
  • Accelerator pedal/lever position sensors
  • Engine brake selector switches
  • Engine coolant level sensor
  • Vehicle speed sensors
  • Feature control switches (i.e. cruise control switches)
  • Fan control switch
  • Air conditioner pressure switch
  • Remote accelerator
  • Remote power-take-off (PTO).

The control system also monitors the following sensors in the aftertreatment system:

  • Aftertreatment diesel oxidation catalyst inlet temperature sensor
  • Aftertreatment diesel particulate filter inlet temperature sensor
  • Aftertreatment diesel particulate filter outlet temperature sensor
  • Aftertreatment diesel particulate filter differential pressure sensor.

Last Modified:  13-Feb-2006