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Thread: U1016

  1. #1
    Lifetime Member mr.prick's Avatar
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    Default U1016

    my car will not start, it keeps cranking and seems to not be getting any spark.
    it will start if i floor the gas peddle but it sputters and reeks of gas.
    FP is fine (60PSI) while cranking, IBPW averages 30.6ms,
    fuses are good, relays are clicking and battery voltage drops to 9volts with a new battery.

    i was getting P1626 but it has not come back.
    i am getting U1016 consistently.
    i can scan/log and upload/download my RR but i can not retrieve the calibration/VIN with the tune.exe,
    it says flashscan is not connected.
    i thought it might be VATS because of the P1626 but, i logged GM.STATE02
    and VATS Fuel Disable is Inactive.
    i now suspect some kind of ground or connector wire has failed. (where?)
    any suggestion is appreciated.

    cranking1.efi

    cranking2.efi
    Last edited by mr.prick; September 10th, 2008 at 01:53 PM.

  2. #2
    Joe (Moderator) joecar's Avatar
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    Default

    My service manual lumps these all together:

    Quote Originally Posted by eSI
    DTC U1001-U1254 : Lost Communications With XXX
    F-body has only 4 modules... you have a loose ground cable or something.

  3. #3
    Lifetime Member mr.prick's Avatar
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    Default

    Quote Originally Posted by joecar View Post
    My service manual lumps these all together:



    F-body has only 4 modules... you have a loose ground cable or something.
    when i check all modules, flashscan sees them.
    i know where the BCM and ASR is,
    where are the other 2 modules and the PCM ground?
    this started after i changed fuel injectors, is there a ground in the injector/coils harness?
    Last edited by mr.prick; August 30th, 2008 at 01:00 PM.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Default F-body

    See post #33 for grounds: showthread.php?t=1913

    Modules:
    - PCM (id $10) -> in RHS of engine bay, near hinge;
    - EBCM/ABS/TCS/ASR (id $28) -> in LHS of engine bay, near fuse panels;
    - SDM/airbag (id $58) -> under console, on trans. tunnel, between gear lever and brake lever;
    - IPC (id $60) -> integral with instrument panel;

    In all cases, if you poke around under the dash/console, make sure battery is disconnected to avoid airbag firing...!!

  5. #5
    Joe (Moderator) joecar's Avatar
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    Default Quote from manual:

    SIR Service Precautions

    Caution

    When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs.


    The inflatable restraint sensing and diagnostic module (SDM) maintains a reserved energy supply. The reserved energy supply provides deployment power for the air bags. Deployment power is available for as much as 1 minute after disconnecting the vehicle power. Disabling the SIR system prevents deployment of the air bags from the reserved energy supply.

  6. #6
    Lifetime Member mr.prick's Avatar
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    thanks joecar.
    i have already taken the steering wheel off and checked the ignition wires.
    i put a resistor between 1073 and 1074 at the BCM but,
    LOL it was the wrong one so the car would not turn over at all.
    i am thinking that the DTC`s are being set because of the
    voltage drop while cranking.
    i know you suggested a bad ground but,
    could the alternator cause this as well?
    Last edited by mr.prick; August 30th, 2008 at 03:30 PM.

  7. #7
    Lifetime Member hquick's Avatar
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    Found some info on U codes.

    Most TACM communication problems can be traced to a bad (or even weak) battery. The second most common cause is bad grounds.
    Howard

    YOU ONLY NEED TWO TOOLS IN LIFE - WD-40 AND DUCT TAPE. IF IT DOESN'T
    MOVE AND SHOULD, USE THE WD-40. IF IT SHOULDN'T MOVE AND DOES, USE THE
    DUCT TAPE.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.


    98 K1500 'HOLDEN' Suburban.
    Custom Whipple SC, Mercruiser Marine intake, 0411 PCM, 4L80E w/shift kit

  8. #8
    Lifetime Member hquick's Avatar
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    Default

    And more:

    Well the only control from the pcm to the alternator is if your vehicle is equipped with a generator control module which started in 2005 and up otherwise the alternator works just liek a alternator suppossed to here is a description on that GCM
    The generator is a serviceable component. If there is a diagnosed failure of the generator it must be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it induces an alternating current (AC) into the stator windings. The AC voltage is then sent through a series of diodes for rectification. The rectified voltage has been converted into a direct current (DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge. The voltage regulator integral to the generator controls the output of the generator. It is not serviceable. The voltage regulator controls the amount of current provided to the rotor. If the generator has field control circuit failure, the generator defaults to an output voltage of 13.8 volts.

    Generator Battery Control Module
    The generator battery control module is a class 2 device. It communicates with the powertrain control module (PCM), instrument panel cluster and the body control module for electrical power management (EPM) operation. It is a serviceable component that is connected to the negative battery cable at the battery. It directly controls the generator field control circuit, charge indicator control, input to the generator. It continuously monitors the generator field duty cycle signal circuit and the battery voltage. If the generator battery control module loses communication with the PCM, the default voltage will be set to 13.8 volts and the module will set U1016. If the generator battery control module loses communication with the body control module (BCM), the module will set U1064.

    Powertrain Control Module (PCM)
    The PCM provides information over the class 2 serial data circuit to the generator battery control module. The generator battery control module monitors the following data parameters provided by the PCM:

    • Intake air temperature

    • Fuel grams per second

    • Throttle position

    • Engine cooling fan speed

    • Engine coolant temperature

    • Exterior Environment - Outside Air Temperature

    The generator battery control module uses these data parameters for different charging system modes depending on the required voltage needed.

    Charge Mode
    The generator battery control module will enter Charge Mode when at least one of the following conditions is met:

    • The electric cooling fans are on high speed.

    • The rear defogger is ON.

    • The battery state of charge is less than 80 percent.

    • The battery current is not between -8 and 15 amps.

    • The estimated ambient air temperature is less than 0°C.

    • DTC B1516 is set.

    Once one of these conditions are met the generator battery control module will set the targeted generator output voltage to the nominal optimum battery voltage which is from 13.9-15.5 volts, the voltage set point is based on the batteries state of charge and estimated battery temperature. The battery voltage ramps up to the targeted set point at a rate of 20 mV per second.

    Fuel Economy Mode
    The generator battery control module will enter Fuel Economy Mode when all of the following conditions are true:

    • Estimated ambient air temperature is equal to or greater than 0°C (32°F).

    • The calculated battery current is less than 15 amperes and greater than - 8 amperes.

    • The battery state of charge is greater than or equal to 80 percent.

    • The rear defoggers are turned OFF.

    • The electric cooling fans are on low speed or OFF.

    The targeted generator output voltage is 13 volts. The generator battery control module will exit this mode once the criteria are met for Charge Mode or it will boost voltage to a pre-determined set point for the fuel pump, headlamps, or windshield wipers.
    Howard

    YOU ONLY NEED TWO TOOLS IN LIFE - WD-40 AND DUCT TAPE. IF IT DOESN'T
    MOVE AND SHOULD, USE THE WD-40. IF IT SHOULDN'T MOVE AND DOES, USE THE
    DUCT TAPE.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.


    98 K1500 'HOLDEN' Suburban.
    Custom Whipple SC, Mercruiser Marine intake, 0411 PCM, 4L80E w/shift kit

  9. #9
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by mr.prick View Post
    thanks joecar.
    i have already taken the steering wheel off and checked the ignition wires.
    i put a resistor between 1073 and 1074 at the BCM but,
    LOL it was the wrong one so the car would not turn over at all.
    i am thinking that the DTC`s are being set because of the
    voltage drop while cranking.
    i know you suggested a bad ground but,
    could the alternator cause this as well?
    Reading Howard's post reminded me that I wanted to say: your log shows voltage falling down to zero... a short in the alternator can cause that.

    When that happens you should see motor stumble followed by instrument panel indicators lighting up;

    What condition is your battery (batteries don't like shorts)...?

    (a dead battery can kill an alternator, and vice-versa).

  10. #10
    Lifetime Member mr.prick's Avatar
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    Default

    the log is while cranking and key on, with a few seconds of key off.
    the battery is new.
    i hope it is a loose ground, that should be easy to find with the info
    from that thread you linked to.
    i'm thinking i pulled the grounds out on the driver's side cylinder head
    when i changed injectors.
    this started right after my injector swap.

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