3406C (PEEC III) Truck Engines Caterpillar

Illustration 1	g00826129
(1) Shutoff solenoid (2) Rack position sensor (3) Engine Data Link connector (4) Rack solenoid (5) Engine speed sensor (6) Transducer module (7) ECM (8) Ground stud on the engine block (9) Coolant temperature sensor (10) Timing solenoid (11) Timing position sensor (12) Vehicle speed sensor (13) Vehicle speed buffer (14) Dash Data Link (15) Throttle position sensor (16) Negative ground through starter or main frame rail (17) Coolant level sensor (18) Diagnostic lamp (19) Warning lamp (20) Clutch switch (21) Brake switch (22) Parking brake switch (23) Cruise control ON/OFF switch (24) Cruise control SET/RESUME switch (25) Battery (26) OEM vehicle wiring harness

The Programmable Electronic Engine Control (PEEC III) uses several electronic input components. These components require an operating voltage. Sometimes, the components require a reference voltage as well. Refer to Electrical Schematics, SENR5509 for the electrical schematics of the PEEC III system.

Grounding Practices

Proper grounding for the vehicle and the engine electrical systems is necessary for proper vehicle performance and reliability. Improper grounding will result in uncontrolled electrical circuit paths and unreliable electrical circuit paths. Uncontrolled engine electrical circuit paths can result in damage to the following components:

• main bearings

• crankshaft bearing journal surfaces

• aluminum components

Uncontrolled electrical circuit paths can cause electrical noise which may degrade the vehicle and the radio performance. To ensure the proper functioning of the vehicle and engine electrical systems, an engine-to-frame ground strap with a direct path to the battery must be used. The direct path to the battery can be accomplished by the following methods.

• starter motor ground

• frame to starter motor ground

• direct frame to engine ground

In any case, an engine-to-frame ground strap must be run from the cylinder head grounding stud to the frame and the negative battery post.

Illustration 2	g00536185
Cylinder head to battery ground (1) Cylinder head ground stud (2) Frame (3) Battery

Illustration 3	g00536186
Alternate cylinder head to battery ground (1) Cylinder head ground stud (2) Negative terminal on starter (3) Frame (4) Battery

The cylinder head must have a wire that is grounded to the battery. Refer to the above illustrations. Ground wires or ground straps should be combined at ground studs that are dedicated for ground use only. The engine grounds should be inspected after every 20125 km (12500 miles) or every 250 hours. All grounds should be tight and free of corrosion. All ground paths must be capable of carrying any likely fault currents. An AWG # 0 or larger wire is recommended for the cylinder head grounding strap. The alternator should be battery ground with a wire size that is capable of managing the full charging current of the alternator.

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NOTICE
When boost starting an engine, follow the instructions in the Operation and Maintenance Manual.

The engine has several input components which are electronic. These components require an operating voltage. Unlike many electronic systems of the past, this engine is tolerant to common external sources of electrical noise. Electro-mechanical buzzers can cause disruptions in the power supply. If electro-mechanical buzzers are used anywhere on the vehicle, the engine electronics should be powered directly from the battery system through a dedicated relay. The engine electronics should not be powered through a common power bus with other key switch activated devices.

Electronic Control Module Power Circuit

The design of the electronic circuits inside the Electronic Control Module (ECM) allows the ordinary switch input circuits to the ECM to have the following characteristics:

• tolerance for resistance between the wires

• tolerance for shorts between wires

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NOTICE
The 12 Volt wire in the data link harness of the ECM is provided to power the PEEC III service tools only. No other devices should be powered by the wire. The ECM was not designed to carry high current loads and is not short circuit protected.

The ECM draws a maximum of 7.5 Amp at 12 Volts from the electrical system of the vehicle. However, PEEC III will function with less than 12 Volts. When the engine is being cranked, the ECM requires a minimum of 6 Volts. When the engine is running, the ECM requires 9 Volts. Power enters the ECM through the positive battery wire and exits through the negative battery wire. Negative battery must be within .5 Volt of the vehicle frame ground. The PEEC III system is protected against power surges on the 12 Volt power supply. The surges are due to the following conditions:

• alternator load dumps

• air conditioner clutches

• jump starting

• other conditions

Engine Speed Input Circuit

Engine speed is sensed by an engine speed sensor. The sensor is similar to other electromagnetic pickups. The signal is generated by placing the sensor near a rotating component, but the sensor requires an operating voltage. The ECM provides the engine speed sensor with an operating voltage of 8.0 ± 0.4 Volts.

The output of the engine speed sensor is a voltage pulse. The pulse's frequency is dependent on the speed of the engine. The frequency of the pulse is interpreted by the ECM as engine speed. The signal's frequency is 10 to 50 Hz when the engine is being cranked. The signal's frequency is approximately 120 Hz at low idle.

Fuel Rack Input Circuit

The engine fuel rack signal is obtained from an electronic linear position sensor which follows the movement of the rack assembly. This sensor requires an operating voltage of 8.0 ± .4 Volts, and a reference voltage of 5.00 ± .25 Volts. These voltages are provided by the ECM.

The output of the Rack Position Sensor is a voltage between .3 and 5.25 Volts. This voltage is dependent upon the position of the rack position sensor. The ECM interprets the voltage as the rack position.

Timing Advance Input Circuit

Engine timing is obtained from an electronic linear position sensor. The sensor follows the movement of the variable timing advance unit. This sensor is very similar to the sensor that is used to read the rack position. The sensor requires an operating voltage of 8.0 ± .4 Volts, and a reference voltage of 5.00 ± .25 Volts. These voltages are provided by the ECM.

The timing position sensor output is a voltage between .3 and 5.25 Volts. This voltage is dependent upon the position of the timing position sensor. The ECM interprets the signal as the timing advance angle.

Boost Pressure Input Circuit

The boost pressure sensor is located in the Transducer Module. Air from the engine inlet manifold is routed to this sensor. This sensor requires an operating voltage of 8.0 ± .4 Volts and a reference voltage of 5.00 ± .25 Volts.

The output of the boost pressure sensor is a DC voltage of .8 to 5.0 Volts. This voltage is dependent upon the pressure on the boost pressure sensor. The ECM interprets the signal as the inlet manifold boost pressure (gauge).

Engine Oil Pressure Input Circuit

The engine oil pressure sensor is also located in the transducer module. Engine oil pressure from the fuel injection pump is routed to this sensor. This sensor also requires an operating voltage of 8 Volts and a reference voltage of 5 Volts.

The output of the oil pressure sensor is a DC voltage of 1.8 to 5.3 Volts. This voltage is dependent upon the engine oil pressure. The ECM interprets the signal as the engine oil pressure.

The oil pressure sensor is designed to measure the engine oil pressure between 0 kPa (0 psi) and 312 kPa (45 psi). Engine oil pressures that are greater than 312 kPa (45 psi)312 kPa (45 psi) are read as 312 kPa (45 psi). This limited oil pressure reading range provides more accurate low oil pressure readings. Low oil pressure readings are more important than high oil pressure readings.

Coolant Temperature Sensor Circuit

Engine coolant temperature is measured by an electronic sensor that is mounted on the water outlet housing. This sensor signal is used to modify the engine's fueling and timing. This allows the ECM to improve the engine's cold start and white smoke cleanup. The ECM supplies the coolant temperature sensor with 5.0 ± .5 Volts (DC). The sensor's output voltage depends on the engine coolant temperature. The sensor's output voltage is .5 to 5.5 Volts (DC).

Coolant Level Input Circuit (OEM Installed)

Coolant level is measured by an electronic sensor that is mounted in the radiator top tank. The sensor is used by the engine protection system to detect the loss of coolant. The ECM supplies 5.0 ± .5 VDC. There are two outputs from the sensor:

• low coolant level

• normal coolant level

If the coolant level is normal, the output of the sensor will be 5 Volts (DC).

Throttle Position Input Circuit

The throttle position is obtained from an electronic sensor that is connected to the accelerator pedal. The 12 Volts operating voltage is provided to the sensor by the vehicle electrical system.

The output of the throttle position sensor is a constant frequency signal with voltage levels of 0 or 5 Volts. The signal's pulse width is dependent upon the arm rotation of the throttle position sensor. The signal's pulse width is interpreted by the ECM as the throttle position. The following chart gives the ECM interpretation of the signal's pulse width.

Table 1

Pulse Width	Throttle Position
15% to 20%	3%
80% to 85%	100%

The arm on the throttle position sensor has a maximum rotation of 45 degrees. The ECM only responds to a 30 degree active zone for interpreting the throttle position. The throttle position sensor has three zones:

• a 5 degree lead in dead zone

• a 30 degree active zone

• a 10 degree lead out zone

Mechanical stops on the accelerator pedal or the pedal linkage should restrict the throttle sensor rotation within the active zone.

Vehicle Speed Input Circuit

Vehicle speed is obtained from an ordinary electromagnetic sensor that reacts to the rotation of the gear teeth in the drive train of the vehicle. The sensor is provided by the vehicle manufacturer.

The output of the vehicle speed sensor is an AC voltage. The voltage could be as much as 50 or 60 Volts. The signal is sent to the vehicle speed buffer. The vehicle speed buffer modifies the signal. The signal is split into two distinctly different signals. One signal is for PEEC III and the other signal is for use by the vehicle manufacturer. The PEEC III signal is a pulsed DC voltage. The signals' output voltage is 0 to 6 Volts. The signal is sent to the electronic control module and the signal is interpreted as the vehicle speed. The other signal is an AC voltage of -9.0 to +9.0 Volts.

The buffer requires an operating voltage of 12 Volts. The voltage is provided by the vehicle's electrical system.

Cruise Control ON/OFF Input Circuit

The cruise control and power take-off ON/OFF input is provided by an ordinary switch. Placing the switch in the ON position activates the cruise control or the PTO if the speed is within the range that is programmed into the ECM for the mode.

With this switch OFF, the input line to the ECM will go to approximately 5 volts. With the switch ON, the input line to the ECM will go to 0 volts (ground).

Cruise Control SET/RESUME Input Circuit

The cruise control and power take off (PTO) SET/RESUME input is provided by a three-position switch. The switch is used to set vehicle speed or engine speed. The purpose of each switch position is given in the following information:

• The center position of the cruise control and power take off (PTO) SET/RESUME input switch is open. The input circuit is inactive.

• If the switch is moved to the SET position and released, the ECM records the vehicle speed. The ECM will maintain that vehicle speed. If the switch is held in the SET position, the ECM will gradually increase the speed. The ECM will increase the speed until the switch is released.

• Cruise control is deactivated by the application of the clutch or the brake. To resume the previous speed, move the switch to the RESUME position and release the switch. If the switch is held in the RESUME position, the ECM will gradually decrease the speed. The ECM will decrease the speed until the switch is released.

With this switch OFF, the input line to the ECM will go to approximately 5 volts. With the switch ON, the input line to the ECM will go to 0 volts (ground).

Brake Switch and Clutch Switch

The brake switch is used to deactivate the cruise control or the PTO operation when the vehicle service brakes are applied. The brake switch is also used to activate the retarder enable output if the service brakes are applied.

The clutch switch is used to deactivate the cruise or PTO modes when the clutch pedal is pressed. The clutch switch is used to deactivate the retarder enable circuit.

When these switches are OFF, the input lines to the ECM will go to approximately 5 volts. When these switches are ON, the input line to the ECM will go to 0 volts (ground).

Shutoff Solenoid Output Circuit

The shutoff solenoid is an output component of the PEEC III system. The shutoff solenoid must be energized before the engine will run. While the engine is being cranked, the ECM supplies battery voltage directly to the solenoid. This eliminates the possibility of a large voltage drop across the PEEC III control system. A large voltage drop could prevent the shutoff solenoid from being fully powered.

The output of the ECM module to the shutoff solenoid is a pulsed voltage. The voltage can reach up to 6 Volts for about one-half second after the ignition switch is turned ON. The 6 Volts are used to pull in the solenoid. After the solenoid is pulled in, the voltage drops to approximately 1.7 Volts.

The PEEC III system is designed to continue operation of the engine with as many faults as possible. There are four faults which will de-energize the shutoff solenoid. De-energizing the shutoff solenoid shuts down the engine. The four faults are given in the following list:

• Loss of engine speed signal

• Engine speed signal of more than 2300 rpm

• A faulty shutoff solenoid

• Loss of electrical power to the ECM

Retarder Enable Output Circuit

The retarder enable output is a positive signal that informs the retarder electronics when everything is safe to turn on the retarder. The status of this signal depends on the following conditions:

• engine rpm

• clutch position

• service brakes

• throttle position

• cruise switch positions

Fuel Rack Output Circuit

The PEEC III system utilizes a rack solenoid (BTM) in order to move the engine fuel rack.

The movements of the rack solenoid (BTM) are proportional to the electrical current flowing through the rack solenoid (BTM). The ECM provides a pulsed voltage of 0 to 3.6 Volts to the rack solenoid (BTM).

The rack solenoid (BTM) moves the engine fuel rack through the movement of the governor servo spool valve and hydraulic pressure.

Engine Timing Output Circuit

The engine timing advance unit is activated by the PEEC III system. A timing solenoid (BTM) is used to move the engine timing advance unit. Movement of the timing advance unit is accomplished through movement of the timing advance spool valve and hydraulic pressure.

The timing solenoid (BTM) is identical to the solenoid that is used by the ECM to position the fuel rack. The ECM sends a pulsed voltage of 0 to 3.6 Volts to the timing solenoid (BTM).

Check Engine Light (Diagnostic) Output Circuit

The check engine light can be used as a diagnostic lamp in order to communicate the status of the electronic control system. The check engine light can be used to communicate the problems of the electronic control system.

When the ECM detects a diagnostic fault, the check engine light will be turned ON. The check engine light will then blink at five second intervals. The light should also be ON and flashing Diagnostic Code 55 whenever the START switch is turned ON, but the engine is not running. This condition will test whether the light is operating correctly.

If the check engine light remains on after the engine starts, the ECM has detected a system fault code. The check engine light or service tools can be used to identify the diagnostic code.

The dash mounted cruise control switches are used to interrogate the ECM for system status. To interrogate the ECM for the system status, use the following procedure:

1. The cruise control switch must be in the OFFposition.

2. Move the cruise control SET/RESUME switch to the RESUME position.

3. The check engine light will begin to flash in order to indicate a two-digit fault code while the SET/RESUME switch is held in the RESUME position.

4. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the fault code. After a two second pause, a second sequence of flashes will occur. The second sequence of flashes represents the second digit of the fault code. After another pause, any additional fault codes will follow. The additional fault codes will be displayed in the same manner.

The check engine light is also used to monitor the idle shutdown timer. The diagnostic lamp will start to rapidly flash ninety seconds before the idle shutdown feature is reached. If the clutch pedal or the service brake pedal is depressed during the final ninety seconds, the idle shutdown timer will be disabled. The idle shutdown timer will stay disabled until the parking brake is reset.

An operating voltage of 12 Volts is supplied to the check engine light from the vehicle electrical system. The ECM turns on the light by connecting one side of the bulb to ground which completes the electrical circuit.

Warning Lamp

The warning lamp is part of the engine protection package. The engine protection package programming determines the state of the light.

• The light can flash.

• The light can be on continuously.

or. The name and color of this lamp is determined by the truck OEM.

Engine Electrical System

The electrical system can have three separate circuits:

• charging circuit

• starting circuit

• low amperage circuit

Some of the electrical system components are used in more than one circuit. The circuits share the following components:

• battery

• circuit breaker

• ammeter

• cables and wires from the battery

The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output in order to keep the battery at full charge.

The starting circuit is in operation only when the start switch is activated.

Both the low amperage circuit and the charging circuit are connected through the ammeter. The starting circuit is not connected through the ammeter.

Charging System Components

Alternator

The alternator is driven by V-belts from the crankshaft pulley. This alternator is a three-phase, self-rectifying charging unit, and the regulator is part of the alternator.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carry current are stationary. The conductors are the following components:

• field winding

• stator windings

• six rectifying diodes

• regulator circuit components

The rotor assembly has many magnetic poles with air space between each of the opposite poles. The poles have residual magnetism (permanent magnets) which produces a small magnetic field between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings. The alternating current (AC) is changed to direct current (DC) when the alternating current (AC) passes through the diodes of the rectifier bridge. Most of the current is used to do the following tasks:

• Charge the battery.

• Supply the low amperage circuit.

The remainder of the current is sent to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. The stronger magnetic field increases the amount of AC current that is produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

The voltage regulator is a solid state electronic switch. The voltage regulator regulates the voltage in the system. The voltage regulator controls the amount of the direct current to the field windings. This allows the alternator to make the needed voltage output.

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NOTICE
Never operate the alternator without the battery in the circuit. Making or breaking an alternator connection with heavy load on the circuit can cause damage to the regulator.

Illustration 4	g00292313
Alternator Components (1) Regulator (2) Roller bearing (3) Stator winding (4) Ball bearing (5) Rectifier bridge (6) Field winding (7) Rotor assembly (8) Fan

Starting System Components

Solenoid

Illustration 5	g00292316
Typical Solenoid Schematic

The solenoid is an electromagnetic switch that does two basic operations:

• The solenoid closes the high current starter motor circuit with a low current start switch circuit.

• The solenoid engages the starter motor pinion with the ring gear.

The solenoid has windings (one or two sets) around a hollow cylinder. A spring loaded plunger (core) is located inside the cylinder. The plunger can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is made. The magnetic field pulls the plunger forward in the cylinder. This moves the shift lever that is connected to the rear of the plunger. The shift lever engages the pinion drive gear with the ring gear. The front end of the plunger then makes contact across the battery and motor terminals of the solenoid. The starter motor then begins to turn the flywheel of the engine.

When the start switch is opened, current no longer flows through the windings. The spring pushes the plunger back to the original position. At the same time, the shift lever moves the pinion gear away from the flywheel.

When two sets of windings in the solenoid are used, the windings are called the hold-in winding and the pull-in winding. Both windings have the same number of turns around the cylinder. In order to produce a stronger magnetic field, a larger diameter wire is used in the pull-in winding.

When the start switch is closed, part of the current flows from the battery through the hold-in winding. The rest of the current flows through the pull-in windings to the motor terminal. The current then goes through the motor to the ground. When the solenoid is fully activated, current is shut off through the pull-in windings. Only the smaller hold-in windings are in operation for the extended period of time that is required to start the engine. The solenoid will now take less current from the battery. The heat that is generated by the solenoid will be kept at an acceptable level.

Starter Motor

The starter motor is used to turn the engine flywheel fast in order to get the engine started. The starter motor has a solenoid. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starter motor so that the engine can not turn the starter motor too fast. When the start switch is released, the starter pinion will move away from the ring gear.

Illustration 6	g00292330
Starter Motor Cross Section (1) Field winding assembly (2) Solenoid (3) Clutch (4) Pinion (5) Commutator (6) Brush assembly (7) Armature

Wiring Diagrams For Grounded Electrical Systems

These systems are used in applications when it is not necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components.

Illustration 7	g00536187
Charging System With Electric Starter Motor (1) Start switch (2) Ammeter (3) Alternator (4) Battery (5) Starter motor

Wiring Diagrams For Insulated Electrical Systems

These systems are most often used in the following applications:

• Applications that require no radio interference

• Protect the grounded components from electrolysis.

The following charts give the correct wire sizes and color codes that are used in the diagrams for grounded and insulated electrical systems.

Illustration 8	g00536188
Charging System With Electric Starter Motor (1) Start switch (2) Ammeter (3) Alternator (4) Battery (5) Starter motor

Table 2

COLOR CODE
B	Black
W	White
R	Red
O	Orange
BR	Brown
LT GN	Light Green
PU	Purple
The number that follows the color code is the recommended size.

Table 3

Correct Wire Sizes
Amp	Wire Size
0 to 18 Amp	14 Gauge
19 to 30 Amp	10 Gauge
31 to 45 Amp	8 Gauge
46 to 65 Amp	6 Gauge
66 to 80 Amp	4 Gauge

Table 4

MAXIMUM RECOMMENDED LENGTH OF BATTERY CABLE
Cable Size	12 Volt Electric Starting	24 to 32 Volt Electric Starting
0	1.2 m (4 ft)	4.6 m (15 ft)
00	1.5 m (5 ft)	5.5 m (18 ft)
000	1.8 m (6 ft)	6.4 m (21 ft)
0000	2.3 m (7.5 ft)	8.2 m (27 ft)