Question about 2009 Honda Accord LX

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Not able to communicate with PCM with diagnostic scanner

Alternator was bad, output 18v, changed it but now it's not charging system. Also has new battery.

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  • Honda Master
  • 20,706 Answers

Did you really check all fuses. (using an ohmmeter)
what engine, I4 or V6?????
are you posting to someone elses PCM Com problem or what?
is this just and alternator issue , how confusing can this be....
PCM> coms. fails.
3 possible.
1: pin 16 in the OBD2 conn, is not 12vdc. blown fuse. (use a voltmeter)
2: wrong scan tool old tool , on modern CAN buss car will fail. 100%
dead. (open SCAN tool book read if it supports CAN buss)
3: Dead PCM or id bet its , a fuse blown to it.

now i do ALT.
18v is bad. (using a quality DMM or radio shack 1960 meter?)
it means the ALT regulator OUT of CONTROL. ( or bad wiring to it)
changed what?, alt is new, used, rebuilt, barrowed? what.?
This car , im looking it up now, at alldata.com so could you,
or the FSM.

this ALT has a regulator, but is just a slave to the PCM.
in that the PCM controls the REG with 3 wires.
the diagnosis is not easy , i recommend, the FSM
it covers all steps., in the diagnosis,

top fail reasons.
1: bad fuses.
2: bad wiring and connections. (see schematic)
3: bad battery (not you) (open cells cause REG to shut down. )
4: bad ALT. (i say a fella change alt 5 times, and skipped #2)
5: bad PCM. (last, , show me that tests, in FSM)

all that and tons more in the FSM. read it.


or log in to alldata.com and read the Charging pages.

Posted on Jan 04, 2014

  • Daniel schluter
    Daniel schluter Jan 04, 2014

    Please disregard this question. Thanks fixkick for the help but I was actually looking for help on my 03 lancer and the site somehow put this other car info down. Thank you for your time.

  • _-__-___-_
    _-__-___-_ Jan 04, 2014

    dont feel badl, this web site has horrible indexing, it dont do makers or years right, it even tries to answer questons for fords with chevy answers.. horrrid.

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Posted on Jan 02, 2017

  • 52 Answers

SOURCE: replaced alternator 23days ago, now battery light

if you have or can gain access to a voltmeter, while the car is running without jumper cables on it hook up the voltmeter to the batter posts and see what the alternator is charging at, a good working alt should charge from 13.5 to 15v, i have seen many new parts go bad fast or be bad from the start

Posted on Mar 12, 2010

duane_wong
  • 6826 Answers

SOURCE: Alternator is not charging battery and it is brand

There's a very good possibility the voltage regulator is bad, but it's on the alternator and usually the whole alternator is replaced when this happens..

Posted on Oct 26, 2010

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Our 2007 Ford Freestyle 3.0V6 shows B1318 code, also scanner shows low battery voltage module. Car shuts off.Please help what to do to fix?


Which module ?

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According to this charging system isn't working correctly ! This is a computer controlled charging system .
Principles of Operation
The powertrain control module (PCM) controlled charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. This system is unique in that it has 2 unidirectional communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated (PWM). The generator communication (GEN COM) line communicates the desired setpoint from the PCM to the voltage regulator. The generator monitor (GEN MON) line communicates the generator load and error conditions to the PCM. The third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.
The charging system voltage is controlled by the PCM. The generator charges the battery and at the same time supplies power for all of the electrical loads that are required. The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to the battery temperature by using a signal from the intake air temperature (IAT) sensor. This means the voltage setpoint is calculated by the PCM and communicated to the regulator by a communication link.
The PCM simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged (the PCM recognizes this and increases the output of the generator to accommodate), the system is also able to increase the idle speed to increase the charge.
To minimize the engine drag when starting the engine, the PCM does not allow the generator to produce any output until the engine has started. The PCM then progressively increases the output of the generator.
The PCM turns the charging system warning indicator off after the engine is started and illuminates it under fault conditions (when the generator is not generating the correct amount of current with the engine running). The charging system warning indicator is also illuminated by the PCM whenever the key is ON with the engine OFF.
This is a System 4 charging system, which uses the GEN MON and GEN COM lines to control and monitor the charging system through the PCM. System 4 charging systems are virtually identical in design and therefore, share the same diagnostics. The circuit numbers and colors may be different, but the functions are the same.

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Can not communicate with PCM via diagnostic scanner


Check for power on pin 16 of the connector.0ff5536b-47c0-4d21-a6b6-52e5ced78256.jpg

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Yes, repair the alternator wire. The pcm does not control alternator output, it only uses and monitors it. I don't know if it is a problem, but maybe from the bad wiring you found may have affected it. Don't know who told you to replace the pcm, but think I'd get a second...well, a third opinion.
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Diagnostic Test Code (DTC) U1000 has a generic description of "Class 2 Serial Data Link Malfunction".
DTC U1064 has a description of "Loss Of Communication With Body Control Module (BCM)"
These codes can be caused by a malfunctioning charging system and should be ignored for now.

DTC P0562 has a description of "System Voltage Low". So this code basicly is only verifying that you indeed have a no-charging problem and that the other codes are most likely also caused by low system voltage.

Although these codes do verify that you have a charging system problem, they are useless in finding out exactly what is wrong with your charging system.

You will need a scan tool that is capable of 2-way communications with the PCM and performing system tests. you will also need a digital multimeter to test the system as you command the generator circuits on with the scanner. If your scanner can do this, let me know and I will get you the troubleshooting instructions for your vehicle. Otherwise, you will have to take it to someone who is properly equipped to diagnose your charging system.

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If you have an engine computer that controls the alternator, you will have to check the wiring from the alt. to the PCM. Also check any fusible links and grounds are often overlooked.
Do you have dual alternators?

SECTION 414-00: Charging System - General Information 2002 E-Series Workshop Manual
DESCRIPTION AND OPERATION Charging System The charging system is a negative ground system consisting of the following:
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  • integral/internal voltage regulator
  • charging system warning indicator
  • storage battery
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The generator is belt-driven by the engine accessory drive system. Refer to wiring diagrams for schematics and locations of the components and wiring.
The battery is a 12 volt direct current source connected in a negative ground system. The battery case is sealed and includes two vent holes to release gases. The battery has three major functions:
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The optional dual generator package (7.3L diesel engine only) consists of an upper/lower dual generator system. The upper generator is a 6G 50/110 generator with a 2.49:1 pulley ratio. The lower generator is a 6G 50/110 generator with a 2.32:1 pulley ratio. Thus the upper and lower generators are not interchangeable.
This system is also monitored and controlled by the powertrain control module (PCM). The PCM monitors both the upper and lower generator I circuits to determine both generators' output and set possible fault codes (diagnostic trouble codes [DTCs]). The PCM only controls the lower generator by turning it on or off by opening or closing the lower generator off only when the glow plugs are commanded on by the PCM to avoid possible damage (excessive voltage) to the glow plugs.
Both generators are independent of one another and only control themselves (through their own internal voltage regulator). If one generator fails, the other generator can maintain system performance under light load conditions. Under a heavy load, the PCM should detect a problem, set a DTC and illuminate the warning indicator.
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jturcotte_1762.gif

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it should notgo over 14 1/2 volts.

Get free DTC codes scan from Autozone. I think you will get DTC code 1246 - System Voltage Malfuction.

The I (indicator) (BAT light) wire activates alternator field circuit.

The heavy B wire circuit sends current to the battery for charing and to run the car.

The S circuit helps control the amount of charge. I suspect yours is not controlling. This car has the PCM (engine computer) help control the output and turn the BAT light on when under or over charging.

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DESCRIPTION AND OPERATION Charging System This vehicle is equipped with a powertrain control module (PCM)-controlled "smart charge" charging system. The PCM-controlled charging system is a system whereby the PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. The PCM-controlled charging system is unique in that it has two uni-directional communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated. The GEN COM line communicates the desired setpoint from the PCM to the voltage regulator and the GEN MON line communicates the alternator load condition to the PCM. The third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.
-------------------------------------
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  • possible causes:
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    • GEN-MON circuit 585 (VT).
    -----------------------------------------------------------------------------------
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    --------------------------------------------------
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    1 Answer

    Alternator problem?


    check battery voltage with engine off. should be @ 12.5v
    check with engine running at about 1500 rpms. It should be @ 14 volts. If yes, it is ok. I think you are ok.
    Please rate higly if htis helps

    your system is more sophisticated than Sars can handle.

    here's how it works.

    The charging system consists of a generator which generates current to supply the vehicle electrical system and maintain the battery in a charged condition.
    The generator is driven by the accessory drive belt. For additional information, refer to Section 303-05 . When the engine is started, the generator begins to generate alternating current (AC) which is converted to direct current (DC) internally. The DC current is controlled by the voltage regulator (located on the back of the generator), and then supplied to the battery.
    The charging system voltage is controlled by the powertrain control module (PCM). The generator charges the battery and at the same time it supplies all the electrical loads that are required. The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to battery temperature by using a signal from the intake air temperature (IAT) sensor. This means that the voltage setpoint is calculated by the PCM and communicated to the regulator by a communication link.
    The PCM simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged the system is able to increase the idle speed.
    To minimize the engine drag when starting the engine, the PCM controls the generator. The generator does not produce any output until the engine has started. The PCM then progressively increases the output of the generator.
    The PCM controls the operation of the charging system warning indicator in the instrument cluster. The PCM is therefore responsible for turning the warning indicator off after the engine is started and illuminating it under fault conditions (when the generator is not generating the correct amount of current with the engine running). The warning indicator will also be illuminated by the PCM at key - on engine off and stall conditions.

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