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Old 04-10-2013, 07:30 AM   #1
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Computer functions

What functions does the computer in a 2007 Ram perform?

I understand it controls:
1. Engine
2. Transmission (automatic)
3. Speedometer
4.
5.
6.
7.
8.
9.
Etc. etc. etc

Anybody know how to get a detailed list of all it's functions?

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Old 04-10-2013, 07:55 AM   #2
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From my 2005 service manual.

OPERATION - PCM
The PCM operates the fuel system. The PCM is a pre-programmed, triple 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.
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, transmission gear selection (automatic transmission),
vehicle speed, power steering pump pressure, 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.

NOTE: PCM Inputs:
ABS module (if equipped)
A/C request (if equipped with factory A/C)
A/C select (if equipped with factory A/C)
A/C pressure transducer
Auto shutdown (ASD) sense
Battery temperature sensor
Battery voltage
Brake switch
J1850 bus (+) circuits
J1850 bus (-) circuits
Camshaft position sensor signal
Crankshaft position sensor
Data link connection for DRB scan tool
8E - 124 ELECTRONIC CONTROL MODULES - SERVICE INFORMATION DR/DH
EATX module (if equipped)
Engine coolant temperature sensor
Fuel level (through J1850 circuitry)
Generator (battery voltage) output
Ignition circuit sense (ignition switch in on/off/crank/run position)
Intake manifold air temperature sensor
Knock sensors (2 on 3.7L engine)
Leak detection pump (switch) sense (if equipped)
Manifold absolute pressure (MAP) sensor
Oil pressure
Oxygen sensors
Park/neutral switch (auto. trans. only)
Power ground
Power steering pressure switch (if equipped)
Sensor return
Signal ground
Speed control multiplexed single wire input
Throttle position sensor
Transfer case switch (4WD range position)
Vehicle speed signal

NOTE: PCM Outputs:
A/C clutch relay
Auto shutdown (ASD) relay
J1850 bus (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge
and speed control warn. lamp
Data link connection for DRB scan tool
EGR valve control solenoid (if equipped)
EVAP canister purge solenoid
Five volt sensor supply (primary)
Five volt sensor supply (secondary)
Fuel injectors
Fuel pump relay
Generator field driver (-)
Generator field driver (+)
Idle air control (IAC) motor
Ignition coil(s)
Leak detection pump (if equipped)
Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
Oxygen sensor heater relays
Oxygen sensors (pulse width modulated)
Radiator cooling fan relay (pulse width modulated)
Speed control vacuum solenoid
Speed control vent solenoid
Tachometer (if equipped). Driven through J1850 circuits.
Transmission convertor clutch circuit. Driven through J1850 circuit
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Old 04-10-2013, 04:53 PM   #3
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And I thought wiring a 3 pin plug was complicated!! My TV repair man used to put tape over the holes in the back of the set to stop me fiddling with my screwdriver.
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Old 04-10-2013, 04:59 PM   #4
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You have no idea the PCM in our truck is simple in comparison to most other newer cars/trucks

Take a Lexus for example 2012 it has something like 47+ computers in it with around 40+ wires each

Our PCM in the trucks controls everything in the eng bay and the evap system for the fuel tank including the pump itself
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Old 04-10-2013, 07:12 PM   #5
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Everything but the ash tray. Is there a specific problem you are looking at?
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Old 04-11-2013, 06:22 AM   #6
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Just wanting to eliminate using the engine and transmission portions of the computer but i seem to need the balance of it's functions. Would like to do away with it entirely.
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Old 04-11-2013, 07:30 AM   #7
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Quote:
Originally Posted by ROLLING THUNDER View Post
Just wanting to eliminate using the engine and transmission portions of the computer but i seem to need the balance of it's functions. Would like to do away with it entirely.
Agreed, this is the problem with installing a stand alone ECM parrallel with our PCM. Our PCM monitor's not only various functions, but the relative values of inputs from say the TPS in relation with the MAP. If the sensor inputs are out of an acceptable range then there is a DTC generated. Meaning if the PCM senses high vacuum condition (MAP) and the TB (TPS) is signaling that it is open, it'll throw a code. I'll have to work through the list of conlicts as the Megasquirt project goes forward.
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1956 Jeep Willys Pickup Hemi powered "Street Rod project"

1# 2017 HTC FASTEST HEMI List....
Current 1/4 mile [email protected] (2018)
Current 60' PB 1.351 (2019) mechanical issue for 1/4m

HTC 2018 TOTY

Support vehicle- 2007 QC G56 4x4 diesel
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Old 04-11-2013, 07:44 AM   #8
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You could get a "Stand Alone" computer for the engine and then swap to a T400 trans. Allot of the fast cars at the track have T400s in them. They're cheaper and Bullet Prof with allot of options. Just saying.......
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Old 04-11-2013, 08:37 AM   #9
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Quote:
Originally Posted by Ghost03hemi View Post
You could get a "Stand Alone" computer for the engine and then swap to a T400 trans. Allot of the fast cars at the track have T400s in them. They're cheaper and Bullet Prof with allot of options. Just saying.......
IMO, from the build stand point a race vehicle is much easier to put together than a street ride. First you need a ECM which is emissions compliant with your vehicle's model year. Even in Virginia where they do not plug in they still look for DTC;s and see if the the dash lights cycle as they should (sometimes). And of course our Rams the PCM has a hand in controling everything but the third light. So keeping the OEM PCM helps keep you street legal. And really all we are looking for is control over Fuel and ignition. Transmissions, IMO are much simpler as they have no associated emission checks. So you can build whatever you want or can afford.
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1956 Jeep Willys Pickup Hemi powered "Street Rod project"

1# 2017 HTC FASTEST HEMI List....
Current 1/4 mile [email protected] (2018)
Current 60' PB 1.351 (2019) mechanical issue for 1/4m

HTC 2018 TOTY

Support vehicle- 2007 QC G56 4x4 diesel
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