Powertrain control module: Difference between revisions

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{{Short description|Automotive component used on motor vehicles}}

{{howto|date=May 2012}}

[[File:An ECM from a 1996 Chevrolet Beretta- 2013-10-24 23-13.jpg|thumbnail|AnA ECUPCM from a 1996 [[Chevrolet Beretta]].]]

{{Merge|Engine control unit|date=October 2013|discuss=Talk:Engine_control_unit#Powertrain_control_module_merge}}

A '''power-train control module''', abbreviated '''PCM''', is an [[automotive industry|automotive]] component, an [[electronica control unit]] (ECU), used on [[motor vehicle]]s. It is generally a combined control unit,controller consisting of the [[engine control unit]] (ECU) and the [[transmission control unit]] (TCU). On some cars, such as many Chrysler'sChryslers, there are multiple computers: the PCM, the Transmission Control UnitTCU, and the Body Control Module (BCM), for a total of three separate computers as an example. These automotive computers are generally very reliable. The PCM commonly controls more than 100 factors in a car or truck. There are many hundreds of error codes that can occur, which indicates that some subsection of the car is experiencing a problem. When one of these errors occurs, usually it will turn on the "check engine" light on the dashboard. The PCM is one of potentially several on-board computers, or essentially the "brain" of the engine control system.<ref>{{cite Whenweb the|url=http://www.aa1car.com/library/pcm.htm "brain"|title=Powertrain doesControl notModule function(PCM) correctly,|publisher=AA1Car neither will the engine or anything else that the microprocessor controls, which may include the charging system, transmission, various emission controls and communications with other on|access-board control modules. The PCM should be replaced only when it is diagnosed to be defective.date=2014-12-20}}</ref>

[[File:An ECM from a 1996 Chevrolet Beretta- 2013-10-24 23-13.jpg|thumbnail|An ECU from a 1996 [[Chevrolet Beretta]].]]

The primary inputs to the PCM come from many sensors, of different types, that are spread around the car. Most of them are oriented toward engine management and performance. These sensors fail at a much higher rate than any of the computers do.

A '''power-train control module''', abbreviated '''PCM''', is an [[automotive industry|automotive]] component, an [[electronic control unit]] (ECU), used on [[motor vehicle]]s. It is generally a combined control unit, consisting of the [[engine control unit]] (ECU) and the [[transmission control unit]]. On some cars, such as many Chrysler's, there are multiple computers: the PCM, the Transmission Control Unit, and the Body Control Module, for a total of three separate computers as an example. These automotive computers are generally very reliable. The PCM commonly controls more than 100 factors in a car or truck. There are many hundreds of error codes that can occur, which indicates that some subsection of the car is experiencing a problem. When one of these errors occurs, usually it will turn on the "check engine" light on the dashboard. The PCM is one of potentially several on-board computers, or essentially the "brain" of the engine control system. When the "brain" does not function correctly, neither will the engine or anything else that the microprocessor controls, which may include the charging system, transmission, various emission controls and communications with other on-board control modules. The PCM should be replaced only when it is diagnosed to be defective.

Early use of the powertrain control module dates back to the late 1970s{{fact|date=February 2017}} - official phasing in{{clarify|date=February 2017}} of the PCM occurred during the early 1980s when used in conjunction with electronic controlled [[carburetor]]s and [[lockup torque converter]]s (at the time conventional 3-speed automatics received lockup converters at the same time overdrives were introduced{{fact|date=February 2017}}).

On board Diagnostic (OBD II) diagnostic trouble codes that typically indicate a fault with the power-train control module include:

*P0600....Serial Communication Link

*P0601....Internal Control Module Memory Check Sum Error

*P0602....Control Module Programming Error

*P0603....Internal Control Module Keep Alive Memory (KAM) Error

*P0604....Internal Control Module Random Access Memory (RAM) Error

*P0605....Internal Control Module Read Only Memory (ROM) Error

*P0606....ECM/PCM Processor

*P0607....Control Module Performance

*P0608....Control Module VSS Output

If you see any of these codes when diagnosing the vehicle with a code reader or scan tool, it may mean the PCM has failed and must be replaced. There can be other reasons for these codes as well, so the presence of any of these codes does not definitively mean the PCM needs to be replaced. Additional diagnostic tests will usually be necessary to confirm the problem is really the power-train control module and NOT something else. Refer to the OEM diagnostic charts for what these tests are. Usually it involves checking certain inputs to the PCM to see if it outputs the correct response. No response or an incorrect response usually means the PCM is defective and needs to be replaced. Professional Automotive Technicians use extremely expensive equipment ($4,000 to $8,000) to do the extensive and complicated diagnostics that are required before eliminating all other possibilities, to be able to arrive at a firm conclusion that the PCM has failed.

The primary inputs to the PCM come from many sensors, of different types, that are spread around the car. Most of them are oriented toward engine management and performance. These sensors fail at a much higher rate than any of the computers do.

==Other names==

'''Engine control unit''' is also called:

* PCM: Power-train control module (Ford/, [[GM Family II engine|GM]], JLR)

* ECM: Engine control module

* Injection control unit ([[Peugeot]],<ref>{{cite web |url=http://www.obdtester.com/psacom-eculist/peugeot/607_1999_2004_van |title = PSA-COM - supported Peugeot 607 1999-2004 VAN control units}}</ref> Citroen[[Citroën]], [[Fiat]], Alfa, [[Lancia]])

* DME/DDE: Digital Motor Electronics / Digital Diesel Electronics ([[BMW]],<ref>{{cite web |url=http://obdtester.com/bimcom-eculist/bmw/5/2008_e60_e61 |title = BimCOM - supported BMW 5 control units}}</ref> [[Mini (marque)|Mini]])

* ECU: Electronic control unit / Engine control unit

==Bibliography==

*{{cite book |first=James E. |last=Duffy |authorlink=|year=2003 |title=Modern Automotive Technology |publisher=Goodheart-Willcox Company |edition=6th |isbn=1-59070-186-0}}

*{{cite book |first=William B. |last=Ribbens |authorlinkauthor-link=William B. Ribbens |edition=6th |year=2002 |title=Understanding Automotive Electronics |publisher=Elsevier |isbn=0-08-048149-3}}

==References==

{{Reflist}}

[[Category:Embedded systems]]

[[Category:Power control]]

[[Category:Engine technology]]