[Latenite1]

- PCM -

MAIN OPERATIONS
​

Many of these operations are identical on both the 5.7L and the 6.1L HEMI engines. (2008-09)

The PCM operates the fuel system. The PCM is a pre-programmed, dual microprocessor digital
computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system,
certain transmission features, speed control, air conditioning compressor clutch engagement and
idle speed.

The PCM can "adapt" its programming to meet changing operating conditions. These conditions
are stored over a short (quick learn) or longer (standard learn) "start cycle" engine periods.

The PCM has two main "modes of operation" and that will be discussed further down.

The PCM receives input signals from various switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations through different system components.

These components are referred to as Powertrain Control Module (PCM) Outputs.
The sensors and switches that provide inputs to the PCM are considered Powertrain Control Module
(PCM) Inputs.

The PCM adjusts ignition timing based upon inputs it receives from sensors that react to:

Engine rpm, manifold absolute pressure, engine coolant temperature, throttle position, pedal
value, transmission gear selection (automatic transmission), vehicle speed and the brake switch.

The PCM adjusts idle speed based on inputs it receives from sensors that react to: throttle
position, vehicle speed, transmission gear selection, engine coolant temperature and from
inputs it receives from the air conditioning clutch switch and brake switch.

Based on inputs that it receives, the PCM adjusts ignition coil dwell. The PCM also adjusts the
generator charge rate through control of the generator field and provides speed control operation.


PCM Inputs:

1. A/C select AND request via CAN communication bus
2. Auto shutdown (ASD) sense
3. Brake switches 1 AND 2
4. Direct Battery voltage
5. EGR Position sensor
6. EVAP purge solenoid current sense
7. Camshaft position sensor signal
8. Crankshaft position sensor
9. CAN C bus communication for internal module communication and ata link connection for scan tools
10. Engine coolant temperature sensor
11. 5 volts (primary)
12. 5 volts (secondary)
13. Fuel level via CAN communication bus from IPM
14. Generator (battery voltage sense) output
15. Ignition circuit sense (ACC AND Run/Start via hardwire from the Total Integrated Power Module (TIPM) while the Crank indication is
via CAN communication bus)
16. Intake manifold air temperature sensor
17. Evaporative system ESIM vacuum switch (if equipped)
18. Manifold absolute pressure (MAP) sensor
19. Oil pressure
20. Oxygen sensors signals
21. Park/neutral switch
22. Power ground
23. Sensor return
24. Signal ground
25. Speed control switch states are determined by SCM and transmitted over the bus via CAN bus
26. SRV position sensor signal
27. Throttle position sensors and Pedal value sensors
28. Transmission pressure switch inputs (42RLE)
29. Transmission variable line pressure sensor (42RLE)
30. Transmission temperature sensor (42RLE)
31. Vehicle speed (ABS equipped) via CAN C bus from ABS module

PCM Outputs

1. Vehicle Speed (Non-ABS) from IPM via CAN C and Trans Turbine sensors (with pinion factor)
2. A/C clutch relay
3. Auto shutdown (ASD) relay coil
4. CAN C bus messages for speedometer (non-ABS packages), voltmeter or generator lamp (if equipped), fuel gauge,
5 oil pressure gauge/lamp, engine coolant temperature gauge and speed control indication warning lamp
6. CAN bus communication for inter module communication and data link connection for scan tools
7. EGR valve control solenoid (if equipped)
8. Electronic Throttle Control (ETC) motor
9. EVAP Purge solenoid
10. Fuel injectors
11. Fuel pump relay
12. Generator field driver
13. Ignition coils
14. Malfunction indicator lamp (also known as MIL). Driven through CAN-Bus Messages.
15. Oxygen sensor heater elements
16. Radiator cooling fan relay via CAN-Bus message to TIPM
17. Short Runner Valve (SRV) actuator (if equipped)
18. Tachometer (if equipped). Driven through Bus Messages.
19. Transmission solenoids (42RLE only)
20. Transmission power relay

PCM (Powertrain Control Module)

also called NGC

​

MODES OF OPERATION
As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate different injector pulse width and ignition timing
for idle than it does for wide open throttle (WOT).

The PCM will operate in two different modes:

1. Open Loop
2. Closed Loop.

During Open Loop modes, the PCM receives input signals and responds only according to preset
PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes.

During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio
is 14.7 parts air-to-1 part fuel.

By monitoring exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse
width. This is done to achieve optimum fuel economy combined with low emission engine performance.

The fuel injection system has the following modes of operation:

1. Ignition switch ON
2. Engine start-up (crank)
3. Engine warm-up
4. Idle
5. Cruise
6. Acceleration
7. Deceleration
8. Wide open throttle (WOT)
9. Ignition switch OFF

The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration and
wide open throttle (WOT) modes are Open Loop modes. The idle and cruise modes, (with the
engine at operating temperature) are Closed Loop modes.


IGNITION SWITCH (KEY-ON) MODE:
This is an Open Loop mode.

When the fuel system is activated by the ignition switch, the following actions occur:

1. The PCM determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy.

2. The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based on this input.

3. Intake manifold air temperature sensor input is monitored.

4. Throttle position sensors (TPS) and pedal value sensors are monitored.

5. The auto shutdown (ASD) relay is energized by the PCM for approximately three seconds.

6. The fuel pump is energized through the fuel pump relay by the PCM. The fuel pump will operate for approximately three seconds unless the engine is operating or the starter motor is engaged.

7. The O2S sensor heater element is energized via the O2S heater drivers (solid state devices) internal to the PCM. These drivers provide a PWM 0-12V signal to heat the O2S heater elements to optimize the O2S sensor signal output. The O2S sensor input is not used by the PCM to calibrate air-fuel ratio during this mode of operation.


ENGINE START-UP MODE:
This is an Open Loop mode. The following actions occur when the starter motor is engaged.

The PCM receives inputs from:

1. Direct Battery voltage
2. Pedal Value Sensors (PVS)
3. Engine coolant temperature sensor
4. Crankshaft position sensor
5. Intake manifold air temperature sensor
6. Manifold absolute pressure (MAP) sensor
7. Throttle position sensors (TPS)
8. Camshaft position sensor signal

The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position
sensor signal within approximately 3 seconds of cranking the engine, it will shut down the fuel injection
system.

The fuel pump is activated by the PCM through the fuel pump relay located in the TIPM.
Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then
control the injection sequence and injector pulse width by actuating ground circuit to each
individual injector on and off.

The PCM determines the proper ignition timing according to input received from the crankshaft
position sensor.

(End of Part 1 of 2)

 

[Latenite1]

- PCM -

MAIN OPERATIONS

Continued from Part 1
​

ENGINE WARM-UP MODE: This is an Open Loop mode.

During engine warm-up, the PCM receives inputs from:

1. Direct Battery voltage
2. Crankshaft position sensor
3. Engine coolant temperature sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Throttle position sensors (TPS)
7. Camshaft position sensor signal
8. Park/neutral switch (gear indicator signal)
9. Pedal Value Sensors (PVS)
10. Air conditioning select signal (if equipped)
11. Air conditioning request signal (if equipped)

Based on these inputs the following occurs:

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.

2. The PCM adjusts engine idle speed through the electronic throttle control (ETC) motor and adjusts ignition timing accordingly.

3. The PCM operates the A/C compressor clutch through the clutch relay. This is done if A/C has been selected by the vehicle operator and requested by the A/C thermostat.

4. When engine has reached operating temperature, the PCM will begin monitoring O2S sensor to control the air/fuel ratio. The system will then leave the warm-up mode and go into closed loop operation.


IDLE MODE:
When the engine is at operating temperature, this is a Closed Loop mode.

At idle speed, the PCM receives inputs from:

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Crankshaft position sensor
5. Engine coolant temperature sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Pedal Value Sensors (PVS)
9. Throttle position sensors (TPS)
10. Camshaft position sensor signal
11. Battery voltage
12. Park/neutral switch (gear indicator signal)
13. Oxygen sensors

Based on these inputs, the following occurs:

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.

2. The PCM monitors the O2S sensor input and adjusts air-fuel ratio by varying injector pulse width. It also adjusts engine idle speed through the electronic throttle control (ETC) motor.

3. The PCM adjusts ignition timing by increasing and decreasing spark advance.

4. The PCM operates the A/C compressor clutch through the A/C clutch relay. This happens if A/C has been selected by the vehicle operator and requested by the A/C thermostat.

CRUISE MODE:
When the engine is at operating temperature, this is a Closed Loop mode.

At cruising speed, the PCM receives inputs from:

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Engine coolant temperature sensor
5. Crankshaft position sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Pedal Value Sensors (PVS)
9. Throttle position sensors (TPS)
10. Camshaft position sensor signal
11. Park/neutral switch (gear indicator signal)
12. Oxygen (O2S) sensors

Based on these inputs, the following occurs:

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then adjust the injector pulse width by turning the ground circuit to each individual injector on and off.

2. The PCM monitors the O2S sensor input and adjusts air-fuel ratio.

3. The PCM adjusts ignition timing by turning the ground path to the coils on and off.

4. The PCM operates the A/C compressor clutch through the clutch relay. This happens if A/C has been selected by the vehicle operator and requested by the A/C thermostat.

ACCELERATION MODE:
This is an Open Loop mode. The PCM recognizes an abrupt increase in throttle position or MAP pressure
as a demand for increased engine output and vehicle acceleration. The PCM increases injector pulse width
in response to increased throttle opening.

DECELERATION MODE:
When the engine is at operating temperature, this is an Open Loop mode.

During hard deceleration, the PCM receives the following inputs.

1. Air conditioning select signal (if equipped)
2. Air conditioning request signal (if equipped)
3. Battery voltage
4. Engine coolant temperature sensor
5. Crankshaft position sensor
6. Intake manifold air temperature sensor
7. Manifold absolute pressure (MAP) sensor
8. Pedal Value Sensors (PVS)
9. Throttle position sensors (TPS)
10. Camshaft position sensor signal
11. Park/neutral switch (gear indicator signal)
12. Vehicle speed

If the vehicle is under hard deceleration with the proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM will enter a fuel cut-off strategy in which it will
not supply a ground to the injectors. If a hard deceleration does not exist, the PCM will determine the
proper injector pulse width and continue injection.

The PCM adjusts ignition timing by turning the ground path to the coils on and off.

WIDE OPEN THROTTLE MODE (WOT)

This is an Open Loop mode. During wide open throttle operation, the PCM receives the following inputs.

1. Battery voltage
2. Crankshaft position sensor
3. Engine coolant temperature sensor
4. Intake manifold air temperature sensor
5. Manifold absolute pressure (MAP) sensor
6. Pedal Value Sensors (PVS)
7. Throttle position sensors (TPS)
8. Camshaft position sensor signal

During wide open throttle conditions, the following occurs:

1. Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off. The PCM ignores the oxygen sensor input signal and provides a predetermined amount of additional fuel. This is done by adjusting injector pulse width.

2. The PCM adjusts ignition timing by turning the ground path to the coil on and off.

OPERATION - IGNITION CIRCUIT SENSE

When the ignition key is inserted, the position of the key is transmitted via the CAN bus to
Integrated Power Module (IPM). When the key position is rotated to the ACC position or
Run/Start position, the IPM energizes the Ignition ACC and/or Run/Start feed which will
wake up the Powertrain Control Module (PCM) accordingly.

These feeds are essentially fused switched battery voltage feeds fabricated by the IPM with
relays or solid state devices. There is not Ignition Start feed to the PCM - this is handled by
a CAN bus message from IPM to PCM. NOTE: Only on those applications with the 42RLE
does the PCM receive an Ignition ACC feed.

IGNITION SWITCH OFF MODE

When ignition switch is turned to OFF position, the PCM stops operating the injectors, ignition
coil, ASD relay and fuel pump relay.

This touches on just some of the basic functions of our PCM.

IF there is interest, I will continue with another added post on the very extensive emissions criteria that the PCM meets.

It is just as elaborate if not more sophisticated on active and passive monitoring of engine components to meet all
Federal emissions standards.

Happy Modding!

 

[agentorange]

WOW!!! No wonder there are no more "shade tree" mechanics around anymore. I was lost after PCM.
agentorange

 

[Houdini]

Yeah, you pretty much need a degree in computers.

 

[IntimidatorR/T]

and it's been like that for several years with these new cars and trucks coming out.

Thank god my degree is in Art Education.. just build it from scratch!

 

[Latenite1]

and it's been like that for several years with these new cars and trucks coming out.

Thank god my degree is in Art Education.. just build it from scratch!

There is more electronic sophistication in the new Dodge Challenger than in
the first Challenger Space Shuttle. With two computer information networks
bridged together (via TIPM) your vehicle can have up to 20 different modules
communicating with each other or the PCM/TCM control systems.

No question that the level of sophistication has risen to an astounding level
and owners need to understand that although, these systems do work at a
high rate of reliability, they are not perfect and are subject to intermittent
and failure operations. Some of it is due to new design and some of it is
due to manufacturing pressures to keep costs low and resultant quality
issues there.

But, when it all does work in concert, you really have a pretty slick operation going on.
Take some time to learn about it.

One of the important thing for a new owner to do with this new Challenger
is read the owners manual. A lot of very useful information is located in
there and it will answer many questions about the operations of the vehicle
before you ask. Yes, I know many (including me) do not have time to sit
and read it from cover to cover, there is another way to help get this
information into the space between the drivers ears. Its called using your
computer and keeping a digital copy of the owners manual available off the
desktop via a shortcut like I do.

Proceed to the link below and download an exact copy of the owners manual
in PDF format and save it in your MyDocuments folder. Then create a shortcut
(in Windows right mouse click on filename) and save the shortcut to your
Desktop, so all you have to do is click it and it opens.

Now you can use the SEARCH window at the top to locate any related
information or topics located in the owners manual in less than a few
seconds, so now, you no longer have the excuse that I do not have time
to look in the owners manual anymore.....

http://www.dodge.com/en/owners/manuals/

You will be glad you took the time to do this.

Happy Modding!

 

[Houdini]

One of the important thing for a new owner to do with this new Challenger is read the owners manual. A lot of very useful information is located in there and it will answer many questions about the operations of the vehicle before you ask.

I couldn't agree more. With every new car, within the first week, I sit in the car and read through the manual cover to cover. When ever I get to something new that previous cars didn't have, I try it out.

It amazes me how many people can drive a car for years before they discover, or more likely someone shows them, a new feature.... like rolling down both front windows using the remote from inside the house.

Some people will label them tips and tricks, but if it's in the manual, it's only seems like a tip or trick special because you didn't read the manual. For those of us who do, it's common knowledge - like using that stick on the left to turn on the turn signals. :surprised:

 

[agentorange]

First car I ever owned that had more pages in its owner's manual than most of the novels I've read in my life. What...457 pages, for a owner's manual!!!! Holy academics, Batman...
agentorange