Question about Pontiac Trans Sport

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I just wanted to confirm that the ECM and the BCM are two different modules in the 1994 3.8L Trans Sport. My Trans Sport is stuck at a local garage where the mechanic had told me he knew how to change out the computers. I finally got him to replace the ECM and it solved the starting problems I was having. It has a memory chip in it that was transferred from the old ECM. When I had the van towed in the radiator fan, heater, interior fan and power windows did not operate. Since then I've been told by mechanics on fixya to have the BCM replaced also to fix that. That's why I want to confirm the difference since my mechanic is working in the dark on this. Thank you!

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  • lonepinesw Jul 30, 2009

    Thank you for all of the information. It should help the mechanic working on my van.

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1 Answer

BCM = Body Control Module

This device integrates all you electrical accesories...It controls your power locks, windows, lighting and factory security system. It is also the comunication hub. Your PCM, airbag cotroller and ABS system are linked to it so they can be accessed by your OBD II connection.

The ECM consists of electronics which are mounted on a multi-layer circuit board. The ECM monitors and adjusts the air/fuel mixture and utilizes a catalytic converter to minimize the amount of pollution produced from the engine. There are two modes of operation, closed loop, which means the computer has completely taking over the operation system. And open loop which is used when the engine is cold and operates on a preset program. The engine must be at operating temperature before it can go into closed loop.The ECM outputs a 5 volt reference to most sensors to drive the monitoring circuits. The ECM also controls the radiator cooling fan, air pump controls, fuel pump, EVAP system and more depending on the vehicle

Posted on Jul 30, 2009

  • Anonymous Jul 30, 2009

    Yes...they are two seperate modules

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2007 Saturn Vue while driving, speedometer stops working and trans starts shifting funny


The electronics involved are unique to say the least .
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the body control module (BCM). The engine control module (ECM) calculates the vehicle speed based on the controlled area network (CAN) serial data message indicating the wheel reference speed from the electronic brake control module (EBCM). The ECM sends a CAN serial data message to the BCM indicating the vehicle speed. The BCM sends a class 2 message to the IPC indicating the vehicle speed.
The speedometer defaults to 0 km/h (0 mph) when any of the following occur:
• The EBCM detects a malfunction in the vehicle speed sensor circuit.
• The ECM detects a loss of CAN communications with the EBCM.
• The BCM detects a loss of CAN communications with the ECM.
• The IPC detects a loss of class 2 communications with the BCM.

Is the ABS light lit ? Having the vehicle checked for DTC'S - diagnostic trouble codes would be the best first step to finding the problem . Could be a wheel speed sensor or ?????? .

May 14, 2017 | Saturn Cars & Trucks

1 Answer

My 2008 Pontiac torrent gage is stuck at the top where the over heating mark is but there is no other indicators that it is overheating what does this mean.


The engine control module (ECM) calculates the engine coolant temperature as determined by the coolant temperature sensor. The ECM sends the engine coolant temperature to the body control module (BCM) via the serial data circuit. The instrument panel cluster (IPC) displays the engine coolant temperature when the BCM sends a serial data message to the IPC indicating the engine coolant temperature. The engine coolant temperature gage defaults to 0° or below if:
• The ECM detects a malfunction in the engine coolant temperature sensor circuit.
• The IPC detects a loss of serial data communications with the BCM.
• The BCM detects a loss of serial data communications with the ECM

The place to start would be to hook up a factory or professional scan tool to see what the actual coolant temperature is ! At the PCM then at the BCM and finally at the instrument cluster . If normal the gauge is bad . The instrument cluster would need to be taken out of the vehicle an sent to be repaired . Or you could buy a used one out of a salvage yard or from on e-bay etc....

Dec 30, 2016 | 2008 Pontiac Torrent

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Where can I find the cruise control fuse on a 2008 hhr


The odds of a fuse being the problem with a non operating cruise control are astronomical . Knowing how the cruise control works is a must in trouble shooting . The different modules involved ,the GMLAN serial data network etc... Here is the factory repair manual description .
Cruise Control Description and Operation
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the cruise control system:
?€¢
The accelerator pedal


?€¢
The brake pedal position (BPP) sensor


?€¢
The body control module (BCM)


?€¢
The cruise on/off switch


?€¢
The + RES switch (equivalent to resume/accel switch)


?€¢
The - SET switch (equivalent to set/coast switch)


?€¢
The engine control module (ECM)


?€¢
The clutch pedal position (CPP) sensor, if equipped with a manual transmission


?€¢
The throttle actuator control (TAC) motor


?€¢
The vehicle speed sensor

The body control module (BCM) monitors the signal circuit of the cruise control switches, which are located on the steering wheel. The BCM relays the cruise control switch status to the engine control module (ECM) via the GMLAN serial data circuit. The ECM uses the status of the cruise control switch to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine the desired vehicle speed. The ECM uses the TAC motor in order to maintain the vehicle speed. For further information on the TAC system, refer to Throttle Actuator Control (TAC) System Description for the 2.2L engine or to Throttle Actuator Control (TAC) System Description for the 2.4L engine.
Ignition voltage is supplied to the cruise control switch from the 2-ampere EPS fuse located in the integrated BCM fuse block. The cruise control function switches are arranged in a resistive ladder design, with each cruise control function switch having a different resistance value. The BCM detects a specific voltage value that is associated with the cruise control function switch being activated. When the normally open cruise control on/off switch is turned ON, the switch closes and the BCM sends a GMLAN serial data message to the ECM indicating that the on/off switch is active. Similarly, when the normally open + RES switch or the normally open - SET switch are pressed, the switch closes and the BCM detects the predetermined voltage signal on the cruise control switch signal circuit. The BCM sends a GMLAN serial data message to the ECM indicating that the + RES switch or the - SET switch is active. The + RES switch or the - SET switch will remain inactive when the BCM has not received the predetermined voltage signal from the on/off switch.
Unless the air bag light is lit too , your best bet would be to take your vehicle to a qualified repair shop.

Aug 09, 2016 | 2008 Chevrolet Chevrolet HHR LT

1 Answer

What does the input sensor on your transmisson of a Pontiac G5 se 2007 do


The speedometer not working wouldn't be caused by an input sensor . The VSS - vehicle speed sensor is a direct input to the PCM , the PCM shares is info over the GMLAN data bus.
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on GMLAN serial data message from the body control module (BCM). The BCM receives vehicle speed data from the powertrain control module (PCM)/engine control module (ECM) via the GMLAN serial data circuit. The speedometer will default to 0 km/h (0 mph) if:
?€¢
The PCM/ECM detects a malfunction in the vehicle speed sensor circuit.


?€¢
The BCM detects a loss of GMLAN communications with the PCM/ECM.


?€¢
The IPC detects a loss of GMLAN communications with the BCM.


The only way to diagnose these problems is with a factory scan tool , this will check inputs an outputs at the PCM an BCM to the instrument cluster . This avoids guessing an playing the parts game. Your best bet would be to take your vehicle to a qualified repair shop .
Same thing with trans not shifting out of first gear , could be a shift solenoid ! Does it shift manually , moving gear selector through the gears ?

Jul 18, 2016 | 2007 Pontiac G5

1 Answer

While driving antitheft light comes on and all the gauges go flat,car keeps runnig,want to disable system,not sure what to look for


Before doing something drastic ,have it checked out for DTC'S - diagnostic trouble codes . It may not be the anti-theft system ,gauges going flat would be more like a communication problem between modules . PCM / BCM / instrument cluster etc.. That also could cause theft light coming on . If your not sure what to look for ,take it to a ASE certified professional . You may render your vehicle useless if you don't know what your doing .
Serial Data Power Mode Master
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle, the PMM is the body control module (BCM). The PMM receives 3 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The 3-wire Ignition Switch table below illustrates the state of these inputs in correspondence to the ignition switch position:
Serial Data Messages The modules that depend exclusively on serial data messages for power modes. stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state, the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state, the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
Indicators and Warning Messages
Refer to Indicator/Warning Message Description and Operation .
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the PCM/ECM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 38?°C (100?°F) if:
?€¢
The PCM/ECM detects a malfunction in the engine coolant temperature sensor circuit.


?€¢
The IPC detects a loss of serial data communications from the BCM.

Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the fuel level. The fuel gage defaults to E (empty) if:
?€¢
The PCM/ECM detects a malfunction in the fuel level sensor circuit.


?€¢
The IPC detects a loss of serial data communications from the BCM.

When the fuel level is less than 14 percent, the low fuel indicator illuminates.
Odometer
The instrument panel cluster (IPC) contains a season odometer and a trip odometer. Momentarily press the trip/reset switch in order to toggle between the season odometer and the trip odometer. Press the trip/reset switch for greater than 2 seconds, while the trip odometer is displayed, in order to reset the trip odometer. The odometer is calculated and stored electronically in the body control module (BCM). The BCM uses the vehicle speed information from the powertrain control module (PCM) to calculate the odometer. The odometer displays 'error' if an internal IPC memory failure is detected. The IPC stores a backup copy of the odometer value incase the IPC stops receiving a valid odometer value from the BCM.
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the ECM/PCM. The IPC receives the vehicle speed information from the BCM via the serial data circuit. The speedometer defaults to 0 kmh (0 mph) when the following occurs:
?€¢
The powertrain control module (PCM) or the engine control module (ECM) detects a malfunction in the vehicle speed sensor circuit.


?€¢
The IPC detects a loss of serial data communication from the BCM.

Tachometer
The instrument panel cluster (IPC) displays the engine speed as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the engine speed. The tachometer will default to 0 RPM if:
?€¢
The PCM/ECM detects a malfunction in the engine speed sensor circuit.


?€¢
The IPC detects a loss of serial data communication from the BCM.

Apr 07, 2016 | 2006 Pontiac G6

1 Answer

Pontiac Montana sv6 2006 electrical or what? Volts keep jump in from 12.3 to 15 while I drive .got stuck on highway 3 times when the voltage hits below 12.1 just swapped the battery...please help


Have your (alternator) Charging system tested ! .This is a computer controlled charging system .
The body control module (BCM) is a class 2 device. It communicates with the powertrain control module (PCM)/engine control module (ECM) and the instrument panel cluster (IPC) for electrical power management (EPM) operation. The BCM determines the output of the generator and sends the information to the PCM/ECM for control of the generator field control circuit. It monitors the generator field duty cycle signal circuit information sent from the PCM/ECM for control of the generator. It monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state-of-charge (SOC). The BCM performs idle boost and load management operations.
Powertrain Control Module (PCM)/Engine Control Module (ECM) The PCM/ECM directly controls the generator field control circuit input to the generator. It monitors the generator's generator field duty cycle signal circuit and sends the information to the BCM. The PCM/ECM will override the BCM control of the generator when one of the following conditions is met:
?€¢
The engine cooling fans are on high speed.


?€¢
There is a high fuel demand.


?€¢
The calculated ambient air temperature is less that 0?°C (32?°F).

Oct 21, 2015 | Pontiac Cars & Trucks

1 Answer

How to advance the timing on a pontiac trans sport 1993 3.8L


the engine timing is preset and is controled by the timing belt, ignition modul and the ECM

Apr 21, 2014 | 1997 Pontiac Trans Sport

1 Answer

Does the BCM in a 1996 plymouth voyager control the ECM?


body control module BCM controls body functions like ac,doors,gauges, and the related while the ECM controls engine management systems, and have little inpact on each other chrysler was the first to network these systems together on a high speed hardwired network ecm relays temp data oil pressure alt voltage and mileage maybe a couple other things i cant remember off the top of my head all that goes to the bcm then is sent to the instrument cluster so it is very possible to have the same problem caused by to seperate modules with that being said in less than a year i think they better look closely at the connectors and pins in the wiring i have have multiple problems with the connectors on these models hope this helps

Dec 05, 2012 | 1996 Plymouth Voyager

2 Answers

What is the difference between an ECM and a BCM? Does a BCM have to be flashed?


The ECM (Electronic control module) runs the engine and the emission control system, the BCM (Body control module) operates most electrical body functions like wipers and interior lights and power windows and door locks plus the security system in may cases, the ECM (on this car now known as the PCM since 1996 by federal mandate) can be flashed, which just a reprogramming of the EPROM chip

Oct 21, 2010 | 2003 Ford Windstar

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