CM870 and ISX Engines – 209-001   System Description

General Information


The Signature and ISX CM870 engine control system is an electronically operated fuel control system that also provides 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.

The control system uses inputs from the operator and its sensors to determine the fueling and timing required to operate at the desired engine speed 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 its 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 engine operating parameters at the time of fault activation is also stored in memory.

Active fault codes will cause a diagnostic lamp to activate to signal the driver.

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

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 on engine operating parameters. These sensors include:

  • Engine coolant temperature sensor

  • Intake manifold air temperature sensor

  • Intake manifold 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

  • EGR valve position sensor

  • EGR temperature sensor

  • Exhaust gas pressure sensor

  • EGR differential pressure sensor

  • Turbocharger speed sensor

  • Turbocharger compressor inlet air temperature sensor.

  • Accelerator pedal/lever position sensor
  • Idle validation switch
  • 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 PTO

NOTE: These inputs are application dependent. Some applications will not use all of these inputs.


Diagnostic Fault Codes


The electronic engine control system can display and record certain detectable fault conditions. These failures are displayed as fault codes, which make troubleshooting easier. The fault codes are retained in the ECM.

There are two types of diagnostic codes:

  • Engine electronic control system fault codes are to inform the operator that there is a problem with the control system that will require troubleshooting.
  • Information and engine protection fault codes are to inform the operator that the control system has detected an engine condition outside the normal operating range.

All fault codes recorded will either be active (fault code is currently active on the engine) or inactive (fault code was active at some time, but is not currently active).

The “Stop” light is red and indicates the need to stop the engine as soon as it can be safely done. The engine must remain shutdown until the fault can be repaired.

The “Warning” light is amber and indicates the need to repair the fault at the first available opportunity.

Maintenance type fault codes, such as water-in-fuel, and maintenance monitor oil change interval, will flash the amber Warning light for 30 seconds after the keyswitch is turned to the ON position.

NOTE: The names and colors of these lamps can vary with equipment manufacturer.


Fault codes can be accessed in at least two different ways; using the electronic service tool, or fault code flash out.

To check for active engine electronic fuel system and engine protection system fault codes, turn the keyswitch OFF and move the diagnostic switch to the ON position.


Turn the vehicle keyswitch to the ON position.

If no active fault codes are recorded, both lights will come on and stay on.

If active fault codes are recorded, both lights will come on momentarily then begin to flash the code of the recorded faults.


The fault code will flash in the following sequence:

  • First, a WARNING (amber) light will flash.
  • Then there will be a short one or two second pause after which the number of the recorded fault code will flash in STOP (red).
  • There will be a one or two second pause between each number.
  • When the number has finished flashing in red, an amber light will appear again.

The lights flash each fault code out three times before advancing to the next code. To skip to the next fault code, move the Increment/Decrement switch (if equipped) momentarily to the increment (+) position. You can go back to the previous fault code by momentarily moving the Increment/Decrement switch (if equipped) to the decrement (-) position. If only one active fault is recorded, the same fault code will continuously be displayed when either (+) or (-) switch is depressed.

The explanation and correction of the fault codes is in Section TF of this manual.


When not using the diagnostic system, turn off the diagnostic switch.


Fault Code Snapshot Data


When a diagnostic fault code is recorded in the ECM, the ECM input and output data is recorded from all sensors and switches. Snapshot data allows the relationships between ECM inputs and outputs to be viewed and used during troubleshooting.

Fault code snapshot data can only be viewed using INSITE™.


INSITE™ Description


INSITE™ is a service tool for the electronic engine control system. Use INSITE™ to:

  • Program customer specified information into the ECM (parameter and features)
  • Aid in troubleshooting the engine
  • Change the engine power or rated speed calibration
  • Transfer new or update calibration files to the electronic engine control system ECM
  • Create and view trip reports, etc.

INSITE™ Monitor Mode


The INSITE™ monitor mode is a useful troubleshooting aid that displays the key ECM inputs and outputs. This feature can be used to spot constant or abnormally fluctuating values.

Last Modified:  08-Oct-2002