QuestionQUESTION: To start off the car runs and dives fine.
When you start the car all the engine lites stay on and none of the guages work.After a day or two the battery is dead.I have been told the computer is not communicating and is running the battery down and is the problem with the guages and all.How do i know what computer is the problem?
I believe it has a ecm, pcm, tcm so what next?? HELP
ANSWER: perform a battery off draw test and see what if anything is staying on.
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QUESTION: How does a person do this battery test?
AnswerBATTERY IGNITION OFF DRAW (IOD)
High current draw on the battery with the ignition OFF will discharge a battery. After a dead battery is serviced the vehicle Ignition Off Draw (IOD) should be checked. Determine if a high current draw condition exists first check the vehicle with a test lamp.
Verify that all electrical accessories are OFF.
Remove key from ignition switch
Turn off all lights
Liftgate and glove box door is closed
Sun visor vanity lights are OFF
All doors are closed
Allow the Illuminated Entry System to time out in approximately 30 seconds, if equipped.
During Transmission Control Module (TCM) power down there will be 500 milliamperes present for 20 minutes. Afterwards less than 1.0 milliampere.
Disconnect battery negative cable Disconnect Battery Negative Cable
CAUTION: Always disconnect the meter before opening a door.
Using an multimeter, that has least a milliampere range of 200 mA. Set meter to the highest mA range. Install meter between the battery negative cable and battery negative post Milliampere Meter Connection Carefully remove the test lamp without disconnecting the meter. After all modules time-out the total vehicle IOD should be less than 25 milliamperes. If ignition off draw is more than 25 milliamperes go to Step 4.
Each time the test lamp or milliampere meter is disconnected and connected, all electronic timer functions will be activated for approximately one minute. The Body Control Module (BCM) ignition off draw can reach 90 milliamperes.
Remove the PDC fuses:
Interior lamps
Brake lamp
IOD
If there is any reading, with fuses removed there is a short circuit in the wiring. Refer to wiring diagrams. If reading is less than 25 mA go to Step 8.
Install all fuses. After installing fuse, the current can reach 90 mA. After time-out the reading should not exceed 25 mA. If OK go to. If not, disconnect:
Radio
Body Control Module
Remote Keyless Entry Module
Disconnect one component at time, to see if any component is at fault. If the high reading is not eliminated there is a short circuit in the wiring. Refer to wiring diagrams.
Remove interior and brake lamp fuses. Install the fuses. The milliampere reading should be 2-4 mA. If reading is higher than 4 mA:
Disconnect PCM.
If reading is OK, replace PCM.
If reading does not change, disconnect the TCM.
If reading is OK, replace TCM.
If reading stays, there is a short circuit to one of the modules. Refer to Wiring Diagrams.
