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Summary of Monitor Information

PCM (JTEC) AND ECM (CM845) MODES (DIESEL)
As input signals in the Engine Control Module (ECM) change, the ECM adjusts its response to output devices. There are several different modes of operation that determine how the ECM responds to the various input signals.


IGNITION SWITCH ON (ENGINE OFF) MODE
When the ignition switch is in the "on" position, the following actions occur:

1. When the PCM and ECM receive an ignition sense input, they power up. Battery voltage is supplied through the battery voltage input.
2. The wait-to start, water-in-fuel, check engine, check gauges, and transmission temperature (auto trans only) lamps are turned on by the PCM, ECM, or BCM for at least 2 seconds as a bulb test. This is done by direct wire or through the Bus to the smart cluster.





3. The ECM monitors the intake air temperature signal. If the intake air temperature is below a predetermined temperature, the ECM will start the air intake preheat cycle. The ECM will energize the intake heaters by grounding the air intake relays. The ECM will turn the wait-to- start lamp on until the preheat cycle is over. If the ECM receives a crank signal before the preheat cycle is over, the preheat cycle will be aborted.
4. The ECM will request the water-in-fuel lamp on if a signal is received from the water-in-fuel sensor.

NOTE: If the water-in-fuel lamp remains illuminated after the 2-second bulb check, the vehicle should not be started until the fuel filter has been drained.

ENGINE START-UP MODE
When the ignition key is held in the "start" position, the following occurs:
1. The ECM receives the crank signal input from the camshaft position sensor.
2. The air intake heaters are not energized during cranking.
3. The ECM monitors engine speed and when the engine speed is above 650 rpm, the ECM determines that the engine is running.




4. If the ECM receives a crank signal before the preheat cycle is over, the heaters will be disabled. However, the post-heat cycle will begin if the engine is in the run state or speed is above 1200 rpm.

ENGINE WARM-UP MODE
1. The ECM may start the air intake heater post- heat cycle depending on intake air temperature. If manifold air temperature was 66 °F or less when the ignition was turned on, the cycle is started.
2. If the transmission temperature sensor shows it is below 59 °F, the automatic transmission will not be allowed to enter overdrive.
3. If the transmission temperature sensor shows it is below 69 °F, the transmission's torque converter clutch will not be allowed to engage.
4. The ECM will request the water-in-fuel lamp on if a signal is received from the water-in-fuel sensor.

CRUISE OR IDLE MODE
During the cruising speed, the following inputs are received by the ECM:
1. The ECM monitors intake manifold air temperature through the intake air temperature sensor.
2. The intake air heater post-heat cycle will be complete, if it is not already over.
3. The vehicle speed, and throttle position sensors are used by the PCM to control the transmission overdrive and torque converter clutch operation.
4. If the transmission temperature sensor shows it is below 59 °F or above 275 °F, the automatic transmission will not be allowed to enter overdrive. If the transmission is in overdrive when the transmission temperature is above 275 °F, the transmission will downshift and not upshift again until the transmission temperature drops to 240 °F.
5. The water-in-fuel sensor signal is used by the ECM to request the water-in-fuel lamp on, if water is sensed in the fuel.

ACCELERATION MODE
When there is an abrupt demand for increased engine output and vehicle acceleration, the following occurs:
1. The vehicle speed, and throttle position signals are used to control transmission overdrive and torque converter clutch operation.
2. If the transmission temperature sensor shows it is below 59 °F, the torque converter clutch will not be allowed to engage.
3. If the transmission temperature sensor shows it is below 59 °F or above 275 °F, the automatic transmission will not be allowed to enter overdrive. If the transmission is in overdrive when the transmission temperature is above 275 °F, the transmission will downshift and not upshift again until the transmission temperature drops to 240 °F.
4. If the speed control system resume/accelerate function is being used, the PCM/ECM (Diesel applications with manual transmission use the CM845 ECM to conduct speed control system) will only allow the vehicle to accelerate at a predetermined rate. If a speed control has been set and the resume/accelerate button is momentarily pushed in, the PCM/ECM will increase vehicle speed by two miles per hour.
5. The PCM/ECM will disable the speed control when:
- the brakes are applied
- excessive engine speed
- the clutch is disengaged (manual transmission)
- the gear selector is shifted to neutral (automatic transmission)
- the speed control off switch is activated

DECELERATION MODE
During deceleration, the following inputs are received by the PCM/ECM:
1. The vehicle speed, crank position, and throttle position signals are used to control transmission overdrive and torque converter clutch operation.
2. The torque converter clutch will disengage, if the brakes are applied.
3. If the transmission temperature sensor shows it is below 59 °F or above 275 °F, the automatic transmission will not be allowed to enter overdrive. If the transmission is in overdrive when the transmission temperature is above 275 °F, the transmission will downshift and not upshift again until the transmission temperature drops to 240 °F.
4. The PCM/ECM will disable the speed control when:
- the brakes are applied
- excessive engine speed
- the clutch is disengaged (manual transmission)
- the gear selector is shifted to neutral (automatic transmission)
- the speed control off switch is activated

IGNITION SWITCH OFF MODE
When the ignition switch is turned to the "off" position, the PCM and ECM still stores in memory trouble codes and the throttle position sensor value from the previous key-on.



FUEL SYSTEM - GENERAL INFORMATION

WARNING: HIGH-PRESSURE FUEL LINES DELIVER DIESEL FUEL UNDER EXTREME PRESSURE FROM THE INJECTION PUMP TO THE FUEL INJECTORS. THIS MAY BE AS HIGH AS 23,200 PSI (1600 BAR). USE EXTREME CAUTION WHEN INSPECTING FOR HIGH-PRESSURE FUEL LEAKS. FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE SKIN CAUSING PERSONAL INJURY OR DEATH. INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF CARDBOARD. WEAR SAFETY GOGGLES AND ADEQUATE PROTECTIVE CLOTHING WHEN SERVICING FUEL SYSTEM.

The fuel system is a Robert Bosch High Pressure Common Rail (HPCR) electronically controlled fuel system. The HPCR system consists of five main components:
* Electronic Fuel Lift Pump
* Fuel Pump Gear Pump
* High Pressure Pump (CP3)
* Fuel Rail
* Injectors

The High Pressure Pump (CP3) supplies high-pressure fuel to the fuel rail independent of engine speed. This high-pressure fuel is then accumulated in the Fuel Rail. High-pressure fuel is constantly supplied to the Injectors by the Fuel Rail. The Electronic Control Module (ECM) controls the fueling and timing of the engine by actuating the Injectors.

Fuel enters the system from the Electronic Fuel Lift Pump, which is attached to the fuel filter assembly. Fuel is forced through the fuel filter element and then enters the Fuel Pump Gear Pump, which is attached to the rear of the High Pressure Pump (CP3). The Fuel Pump Gear Pump is a low-pressure pump and produces pressures ranging from 80 - 180 psi (5.5 - 12.4 bar).

Then the fuel enters the High Pressure Pump (CP3). The low-pressure fuel is then supplied to the Fuel Control Actuator (FCA). The Fuel Control Actuator is an electronically controlled solenoid valve. The ECM controls the amount of fuel that enters the high pressure pumping chambers by opening and closing the Fuel Control Actuator based on a demanded fuel pressure. The Pressure Sensor on the Fuel Rail provides the actual fuel pressure. when the Actuator is opened, the maximum amount of fuel is being supplied to the High Pressure Pump. Any fuel that does not enter the High Pressure Pump is directed to the Cascade Overflow Valve. The Cascade Overflow Valve regulates how much excess fuel is used for lubrication for the pump and how much is returned to the tank.

The fuel that enters the High Pressure Pump is pressurized between 4350 - 23,200 psi (300 - 1600 bar) by three radial pumping chambers. The pressurized fuel is then supplied to the Fuel Rail.
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