3412 (PEEC) INDUSTRIAL ENGINE ELECTRONIC TROUBLESHOOTING Caterpillar

Glossary Of PEEC Terms

Usage:

Actual Rack

The ECM's interpretation of the signal from the Rack Position Sensor, read as "Rack Pos" on the ECAP...

Actual Timing Advance

Degrees of advance beyond (basic) static timing.

Aftermarket device

A device or accessory installed by the customer after the engine is delivered.

Alternating Current (AC)

The direction of current flow changes (alternates) regularly and constantly.

American Wire Gauge (AWG)

A measure of the diameter (and therefore the current carrying ability) of electrical wire. The smaller the AWG number, the larger the wire.

Before Top Dead Center (BTDC) or Before Top Center (BTC)

The 180° of crankshaft rotation before the piston reaches Top Dead Center (normal direction of rotation).

Boost Pressure Sensor

This sensor measures inlet manifold air pressure and sends a signal to the ECM.

Brushless Torque Motor (BTM)

Solenoid used to move fuel rack servo pool valve also called the Rack Solenoid.

Bypass Circuit

A circuit, usually temporary, to substitute for an existing circuit, typically for test purposes.

Calibration

As used here, is an electronic adjustment of a sensor signal.

Code

See Diagnostic Code.

Customer Specified Parameter

A Parameter that can be changed and whose value is set by the customer.

Coolant Temperature Sensor

Used in 3412 PEEC to set Cold Mode and to trigger the shift out of Cold Mode during engine warmup.

Data Link

An electrical connection for communication with other microprocessor based devices that are compatible with the American Trucking Association and SAE Standards. The Data Link is also the communication medium used for programming and troubleshooting with Caterpillar service tools.

Desired Rack Position ("Des Rack Pos" on ECAP)

The rack setting calculated by the ECM as needed to attain or maintain the Desired RPM.

Desired RPM

An input to the electronic governor within the ECM, and the output signal from the engine control logic within the ECM. The engine control logic uses inputs from the Throttle Position Sensor, Engine Speed Sensor, Cold Mode, and Customer Parameters to determine "Desired RPM".

Desired Timing Advance ("Des Timing Adv" on ECAP)

The injection timing advance calculated by the ECM as required to meet emission and performance specifications.

Diagnostic Code

Sometimes referred to as a "fault code", it is an indication of an existing problem in the PEEC system.

Diagnostic Lamp

Sometimes referred to as the "check engine light", it is used to warn the operator of the presence of an active diagnostic code.

Direct Current

The direction of current flow is consistently in one direction only.

Duty Cycle

Same as Pulse Width Modulation.

Electrically Erasable Programmable Read Only Memory (EEPROM)

A large scale integrated-circuit chip for storing digital data. It can be electronically erased and reprogrammed. Used to store PEEC parameters that can be changed using the ECAP.

Electronic Control Analyzer and Programmer (ECAP)

A Caterpillar service tool used to program and for diagnosis of a variety of electronic controls.

Electronic Control Module (ECM)

The engine control computer that provides power to the PEEC electronics, monitors PEEC inputs and acts as a governor to control engine rpm.

Engine Speed Sensor

A magnetic sensor that measures engine speed from the rotation of the fuel injection pump camshaft (slotted retainer).

Estimated Dynamic Timing

Estimated actual injection timing. Calculated internally by PEEC.

Est. Dyn Timing = Static Timing Spec + Actual Timing Advance + Port effect (.2 deg/100 rpm).

The ECM's estimate of actual injection timing.

Fuel-Air Ratio Control (FARC) or Fuel Ratio Control (FRC)

FRC rack - a rack limit based on fuel-to-air ratio, to limit emissions during acceleration. As PEEC senses a higher boost pressure (more air into the cylinder) it increases the FRC rack limit (allows more fuel into cylinder). It works much like the FRC on a mechanical governor.

FUEL OFF and FUEL ON

Refers to minimum fuel and maximum fuel positions of the fuel rack.

Harness

The wiring bundle connecting all components of the PEEC system.

Hertz (Hz)

Measure of frequency in cycles per second.

Inlet Air Pressure Sensor

Measures changes in atmospheric pressure.

Jacket Water Aftercooler (JWAC)

A means of cooling intake air after the turbocharger, using jacket water for cooling. The intake air is passed through an aftercooler (heat exchanger) before going to the intake manifold.

Oil Pressure Sensor

This sensor measures engine oil pressure and sends a signal to the ECM.

Open Circuit

Condition where an electrical wire or connection is broken, so that the signal or the supply voltage can no longer reach its intended destination.

Parameter

A programmable value which affects the characteristics or behavior of the engine.

Password

A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The PEEC system requires correct passwords in order to change Customer Specified Parameters (Customer Passwords) or certain engine specifications (Factory Passwords). Passwords are also required to clear certain diagnostic codes.

Personality Module or Ratings Personality Module

The module connected to the ECM which contains all the instructions (software) for the ECM, logged diagnostic codes, and performance maps for a specific horsepower family.

Programmable Electronic Engine Control (PEEC)

The complete electronic system that monitors and controls engine operation under all conditions.

Programmable Read Only Memory (PROM)

A large scale integrated-circuit chip for storing digital data. It can be programmed only at the factory. Used in the PEEC personality module to store control logic and rating information.

Pulse Width Modulation (PWM)

A signal consisting of variable width pulses at fixed intervals, whose "TIME ON" versus "TIME OFF" can be varied (also referred to as "duty cycle").

Example of Pulse Width Modulation Signals

Rated Rack Position

A limit on rack position which provides the specified horsepower and torque curves. This value comes from maps programmed into the personality module at the factory.

Rack Position Sensor

A linear position sensor which follows movement of the rack assembly and sends an electrical signal to the ECM.

Rack Solenoid (BTM)

A rotary proportional solenoid (also called a BTM - Brushless Torque Motor) used to move the fuel rack servo spool valve.

Reference Voltage

A regulated voltage supplied by the ECM to a sensor. The reference voltage is used by the sensor to generate a signal voltage.

Sensor

A device used to detect and convert a change in pressure, temperature, or mechanical movement into an electrical signal.

Service Program Module (SPM)

A software program on a factory programmable computer chip, designed to adapt an ECAP to a specific application.

Short Circuit

A condition where an electrical circuit is unintentionally connected to an undesirable point. Example: a wire which rubs against the support frame until it makes electrical contact.

Signal

A voltage or waveform used to transmit information, typically from a sensor to the ECM.

Speed "burp"

A sudden brief change in engine speed.

Static Timing Specification

Fixed number of degrees determined by design of the fuel pump camshaft (determines injection timing with no advance). Note that the value displayed is the specification for static timing, NOT an electrically measured value.

Subsystem

As used here, it is a part of the PEEC system that relates to a particular function, for instance: rack subsystem.

Supply Voltage

A constant voltage supplied to a component to provide electrical power for its operation. It may be generated by the ECM, or it may be battery voltage supplied by the system wiring.

"T" Harness

A test harness designed to permit normal circuit operation while measuring voltages, typically inserted between the two ends of a connector.

Throttle Position

The ECM's interpretation of the signal from the throttle position sensor.

Throttle Control Sensor

An electronic sensor which is connected to the throttle control PC and sends a Pulse Width Modulated Signal to the ECM.

Total Tattletale

Total number of changes to all customer specified parameters.

Transducer

A device that converts a mechanical signal to an electrical signal.

Transducer Module

A sealed unit mounted below the rack actuator housing and contains the engine Oil Pressure Sensor, Boost Pressure Sensor and Protective signal conditioning circuitry.