Need help!!

[amanda8633]

I have a 2002 Jeep Liberty. I have got a new battery and a new alternator. All ran fine for almost 2 weeks. Now over night my battery is being drained. All lights are off. What could it be??

 

[SteelHeadz]

Welcome to Jeepz. Does it start when you jump or charge the battery?, aftermarket electronics tends to also contribute to a battery draw like a radio, amplifier, mobile phone etc. A parasitic battery drain can be tracked down by installing a multimeter between the neg. battery cable and the ground. Set the amperege on the meter at 200ma setting then move it down slowly to make sure you dont blow the fuse in the meter. The reading will be high when you first turn the meter on with all the electrical components in the vehicle shut off. After a few minutes when the modules in the vehicle goes in a sleep mode the amp readings should drop close to zero. If not, start pulling the fuses one at a time while monitoring the meter readings. make sure all the doors are closed as you do this, otherwise the body control module will wake up and also ping the other modules to go on a standby mode and this will invalidate the test.

 

[amanda8633]

we did the test. when one of the three "jb" fuses was removed the amperage dropped. With that fuse removed the car runs but there is no radio or turning signals. what does that mean now?

 

[SteelHeadz]

we did the test. when one of the three "jb" fuses was removed the amperage dropped. With that fuse removed the car runs but there is no radio or turning signals. what does that mean now?

That means the drain is in the radio or the turn signal circuit. I would think it would be on the radio circuit. Is it the factory radio or aftermarket? and what was the fuse number?, i could look at a schematic diagram and see what all it's connected to.

 

[amanda8633]

The radio is the factory radio. The fuse i pulled was jb power 11. I just noticed that on the fuse box it says there should be a fuse in jb power 7 and 15 not 11. the fuse was in 11 and none in 7. would that make a difference?

 

[SteelHeadz]

Ok, Fuse 11 on the JB is strictly for the hazard switch and combo flasher. Fuse 15 is for the A/C clutch and fuel pump relay control. Fuse 7 is for the brake lamps, heated seat module if equipped and BCM. Part of the fuse 11 is the dome lamp and dimmer circuit. Are you sure the dome lamps aren't swithed on over ride position?

 

[amanda8633]

they are not in the override in position. i left the fuse out all nite and the battery did not drain. can you post the schematic. when the fuse is pulled the radio does not work.

 

[SteelHeadz]

 

[MudderChuck]

Just an oddball hunch, open the glovebox, touch the bulb quickly with your finger and see if it is hot. Be careful it may be real hot.

 

[amanda8633]

what does the bcm control?

 

[SteelHeadz]

The microprocessor-based Body Control Module (BCM) monitors many hard wired switch and sensor inputs as well as those resources it shares with other electronic modules in the vehicle through its communication over the Programmable Communications Interface (PCI) data bus network. The internal programming and all of these inputs allow the BCM microprocessor to determine the tasks it needs to perform and their priorities, as well as both the standard and optional features that it should provide. The BCM programming then performs those tasks and provides those features through both PCI data bus communication with other electronic modules and through hard wired outputs through a number of driver circuits, relays, and actuators. These outputs allow the BCM the ability to control numerous accessory systems in the vehicle.
The BCM operates on battery current received through a fuse in the Junction Block (JB) on a non-switched fused B(+) circuit, through another fuse in the JB on a fused ignition switch output (run-start) circuit, and through a third fuse in the JB on a fused ignition switch output (run-acc) circuit. This arrangement allows the BCM to provide some features regardless of the ignition switch position, while other features will operate only with the ignition switch in the On, Start, and/or Accessory positions. All of the battery current circuits are connected to the BCM through the JB/BCM connector. The BCM receives ground through five separate circuits. Three of these circuits are connected to the BCM through a connector and take out of the instrument panel wire harness on three separate ground circuits, while the other two circuits are connected to the BCM through the JB/BCM connector. All of these circuits are grounded through a splice block located in the instrument panel wire harness with an eyelet terminal connector that is secured by a nut to a ground stud on the driver side instrument panel end bracket near the JB.
The BCM monitors its own internal circuitry as well as many of its input and output circuits, and will store a Diagnostic Trouble Code (DTC) in electronic memory for any failure it detects. These DTCs can be retrieved and diagnosed using a DRBIII® scan tool.
HARD WIRED INPUTS
The hard wired inputs to the BCM include the following:

• A/C on/off control</B>
• Ambient temperature sensor signal</B>
• Body control module flash enable</B>
• Door lock switch mux</B>
• Driver door ajar switch sense</B>
• Flip-up glass ajar switch sense</B>
• Flip-up glass release switch sense</B>
• Fog lamp switch sense</B>
• Front wiper park switch sense</B>
• Front wiper switch mux</B>
• Front washer pump driver</B>
• Fused B(+)</B>
• Fused ignition switch output (run-acc)</B>
• Fused ignition switch output (run-start)</B>
• Headlamp switch mux</B>
• High beam switch sense</B>
• Hood ajar switch sense - premium with VTSS - in markets where required only</B>
• Key-in ignition switch sense</B>
• Left cylinder lock switch sense - premium with VTSS only - omitted in some markets as required</B>
• Panel lamps dimmer switch mux</B>
• Passenger doors ajar switch sense (input from three ajar switches connected in parallel)</B>
• Radio control mux - premium with remote radio switches only </B>
• Rear courtesy lamp control</B>
• Rear window defogger control</B>
• Rear wiper intermittent driver</B>
• Rear wiper on driver</B>
• Right cylinder lock switch sense - premium with VTSS only - omitted in some markets as required</B>
• RKE antenna (two circuits) - premium with RKE only</B>
• Tailgate ajar switch sense</B>
• Tailgate cylinder lock switch sense</B>
• Vehicle speed sensor</B>

HARD WIRED OUTPUTS

The hard wired outputs of the BCM include the following:

• Courtesy lamp driver</B>
• Courtesy lamp load shed</B>
• Door lock relay control</B>
• Driver door unlock relay control - premium with RKE only </B>
• Flip-up glass release motor driver</B>
• Front fog lamp relay control - premium with front fog lamps only</B>
• Front wiper high/low relay control</B>
• Front wiper on/off relay control</B>
• Hazard lamp control</B>
• High beam relay control</B>
• Horn relay control - premium with RKE only</B>
• Instrument cluster wake up signal</B>
• Low beam relay control</B>
• Park lamp relay control</B>
• Passenger door unlock relay control</B>
• Rear fog lamp relay control - premium with rear fog lamps in markets where required only</B>
• Rear window defogger relay control</B>
• RKE supply - premium with RKE only</B>
• Tailgate lock driver</B>
• Tailgate unlock driver</B>
• Vehicle speed output</B>
• Vehicle speed sensor supply</B>
• VTSS indicator driver - premium with VTSS only</B>

GROUNDS

The BCM receives ground through five separate circuits, and also supplies a ground path to several switches through the following hard wired circuits:

• Ambient temperature sensor return</B>
• Door lock switch ground</B>
• Headlamp switch return</B>
• Radio control mux return</B>
• RKE ground - premium with RKE only</B>
• Tailgate switch ground</B>

COMMUNICATION

Not including the two RKE antenna circuits (RKE antenna + and –), which merely pass through the premium BCM from the RKE module to the external RKE antenna in the instrument panel wire harness, the BCM has the following communication circuits:

• PCI bus</B>
• RKE program serial data - premium with RKE only</B>
• RKE transmit serial data - premium with RKE only</B>

MESSAGING

The BCM uses the following messages received from other electronic modules over the PCI data bus:

• Battery Temperature (PCM)</B>
• Compass Mini-Trip Computer Button Status (CMTC) - premium only</B>
• Coolant Temperature (PCM)</B>
• Distance Pulses (PCM)</B>
• Engine Speed (PCM)</B>
• Fuel Tank Level (PCM)</B>
• Fuel Used (PCM)</B>
• Intrusion Transceiver Module Commands (ITM) - premium in markets where required only</B>
• Manifold Absolute Pressure (PCM)</B>
• OK to Lock - Rolling Locks (PCM)</B>
• SKIS Status (SKIM)</B>
• Vehicle Identification Number (PCM)</B>
• Vehicle Speed (PCM)</B>

The BCM provides the following messages to other electronic modules over the PCI data bus:

• A/C Select Switch Status (PCM)</B>
• Country Code (EMIC, PCM, CMTC)</B>
• Distance to Empty (CMTC) - premium only</B>
• Door Ajar Status (EMIC)</B>
• Exterior Lighting Status (EMIC)</B>
• Flip-up Glass Ajar Status (EMIC)</B>
• Fuel Economy (Average and Instantaneous) (CMTC) - premium only</B>
• Hood Ajar Status (ITM) - premium in markets where required only</B>
• Ignition On Timer (CMTC) - premium only</B>
• Intrusion Transceiver Module Commands (ITM) - premium in markets where required only</B>
• Key-In Ignition Switch Status (EMIC)</B>
• Outside Temperature (CMTC) - premium only</B>
• Panel Lamp Intensity (CMTC, Radio)</B>
• Tailgate Ajar Status (EMIC)</B>
• Radio Mode (Radio) - premium only</B>
• Radio Preset Scan (Radio) - premium only</B>
• Radio Seek Down (Radio) - premium only</B>
• Radio Seek Up (Radio) - premium only</B>
• Radio Volume Down (Radio) - premium only</B>
• Radio Volume Up (Radio) - premium only</B>
• Vacuum Fluorescent Display Synchronization (CMTC, EMIC, Radio)</B>
• Vehicle Theft Security System Status (PCM, ITM) - premium only</B>

There are two different versions of the BCM: base and premium. The base BCM is a subset of the components in the premium version. Basically, the base version BCM does not support the following features: Compass Mini-Trip Computer (CMTC), fog lamps (front and/or rear), Remote Keyless Entry (RKE), remote radio switches, or Vehicle Theft Security System (VTSS). Both versions of the BCM utilize integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network along with many hard wired inputs to monitor many sensor and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the BCM allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the PCI data bus. The electronic functions and features that the BCM supports or controls include the following:

• A/C Select Switch Status</B> - The BCM monitors an input from, and transmits the status of the A/C switch on the heater-A/C control.
• Ambient Temperature Data</B> - The premium BCM monitors and transmits the ambient temperature sensor input data.
• Cargo Lamp Disable</B> - The BCM monitors an input from the cargo lamp switch to provide an interior lighting disable feature.
• Chimes</B> - The chime tone generator is located on the ElectroMechanical Instrument Cluster (EMIC) circuit board, but the EMIC goes to sleep with the ignition switch in the Off position. The BCM provides a wake-up output to the EMIC based upon inputs from the key-in ignition switch or the exterior lighting switch, then sends electronic chime request messages to the EMIC for the headlamps-on warning and key-in ignition warning.
• Door Lock Inhibit</B> - The BCM monitors the key-in ignition switch and the driver side front door ajar switch to provide a door lock inhibit feature.
• Exterior Lamp Load Shedding</B> - The BCM provides a battery saver feature which will automatically turn off exterior lamps that remain on after a timed interval.
• Exterior Lamp Status</B> - The BCM monitors the status of the park lamp, low beam, high beam or Daytime Running Lamp (DRL - Canada only), front fog lamp (optional), and rear fog lamp (in required markets only) relays.
• Exterior Lighting Control</B> - The BCM provides exterior lamp control for standard head and park lamps, as well as Daytime Running Lamps (DRL - Canada only), front fog lamps (optional), and rear fog lamps (in required markets only). This includes support for features including optical horn (also known as flash-to-pass) and headlamp time delay.
• Flip-Up Glass Control</B> - The BCM monitors the tailgate cylinder lock switch, the tailgate handle switch, the Remote Keyless Entry (RKE) module inputs and the rear wiper switch to provide control for the rear flip-up glass actuator.
• Fog Lamp Control</B> - The premium BCM provides fog lamp control for front fog lamps (optional), and rear fog lamps (in required markets only).
• Front Wiper System Status</B> - The BCM monitors the status of the front wiper motor park switch.
• Fuel Economy and Distance to Empty Calculations</B> - The BCM calculates and transmits the fuel economy and Distance To Empty (DTE) data.
• Headlamp Time Delay</B> - The BCM provides a headlamp time delay feature with the ignition switch in the Off position.
• Heated Rear Glass Control</B> - The BCM provides control and timer functions for the heated rear glass feature and transmits the system status.
• Ignition On/Off Timer</B> - The BCM monitors and transmits the elapsed ignition On timer data and monitors the ignition Off time.
• Ignition Switch Position Status</B> - The BCM monitors and transmits the status of the ignition switch.
• Instrument Panel Dimming</B> - The BCM monitors and transmits the selected illumination intensity level of the panel lamps dimmer switch.
• Interior Lamp Load Shedding</B> - The BCM provides a battery saver feature which will automatically turn off all interior lamps that remain on after a timed interval.
• Interior Lighting Control</B> - The BCM monitors inputs from the interior lighting switch, the door ajar switches, the flip-up glass ajar switch, the tailgate ajar switch, the cargo lamp switch, the reading lamp switches, and the Remote Keyless Entry (RKE) module to provide courtesy lamp control. This includes support for timed illuminated entry with theater-style fade-to-off and courtesy illumination defeat features.
• Intermittent Wipe and Front Wiper System Control</B> - The BCM monitors inputs from the front wiper and washer switch and the front wiper motor park switch to provide front wiper system control through the wiper on/off and high/low relays. This includes support for adjustable intermittent wipe, mist wipe (also known as pulse wipe), and wipe-after-wash features.
• Key-In-Ignition Switch Status</B> - The BCM monitors and transmits the status of the key-in-ignition switch.
• Panic Mode</B> - The BCM provides support for the Remote Keyless Entry (RKE) system panic mode feature.
• Parade Mode</B> - The BCM provides a parade mode (also known as funeral mode) that allows the interior Vacuum Fluorescent Displays (VFD) to be illuminated at full intensity while driving in daylight with the exterior lamps On.
• Power Locks</B> - The BCM monitors inputs from the power lock switches and the Remote Keyless Entry (RKE) module (optional) to provide control of the power lock motors through outputs to the lock, unlock, and driver unlock (RKE only) relays. This includes support for rolling door locks (also known as automatic door locks) and a door lock inhibit mode.
• Programmable Features</B> - The BCM provides support for several standard and optional programmable features, including: rolling door locks, headlamp time delay interval, Remote Keyless Entry (RKE) driver-door-only or unlock-all-doors, RKE optical chirp, and RKE audible chirp.
• Remote Keyless Entry</B> - The premium BCM provides the optional Remote Keyless Entry (RKE) system features, including support for the RKE Lock, Unlock (with optional driver-door-only unlock, and unlock-all-doors), rear flip-up glass control, Panic, audible chirp, optical chirp, and illuminated entry modes, as well as the ability to be programmed to recognize up to four RKE transmitters.
• Rolling Door Locks</B> - The BCM provides support for the power lock system rolling door locks feature (also known as automatic door locks).
• Tailgate and Flip-Up Glass Ajar Status</B> - The BCM monitors and transmits the status of the tailgate and rear flip-up glass ajar switches.
• Remote Radio Switch Interface</B> - The premium BCM monitors and transmits the status of the optional remote radio switches.
• Self-Diagnostics</B> - The BCM provides support for diagnostics through communication with the DRBIII® scan tool over the PCI data bus network. Each analog and digital input can be verified, and each output can be actuated through the use of this diagnostic protocol. The BCM also stores Diagnostic Trouble Codes (DTCs) to assist in troubleshooting this unit.
• Vacuum Fluorescent Display Synchronization</B> - The BCM transmits panel lamp intensity data which allows modules with Vacuum Fluorescent Displays (VFD) to coordinate their illumination intensity.
• Vehicle Speed System</B> - The BCM monitors a vehicle speed input from the vehicle speed sensor (without Antilock Brake System [ABS]) or from the Controller Antilock Brake (CAB)(with ABS), calculates the vehicle speed based upon a programmed axle ratio/tire size (electronic pinion factor), and transmits the vehicle speed information to the Powertrain Control Module (PCM) on a hard wired output circuit.
• Vehicle Theft Security System</B> - The premium BCM monitors inputs from the door cylinder lock switches, the tailgate cylinder lock switch, the door ajar switches, the tailgate ajar switch, the flip-up glass ajar switch, the hood ajar switch (in required markets only), and the Remote Keyless Entry (RKE) module to control the features of the optional Vehicle Theft Security System (VTSS).

Hard wired circuitry connects the BCM to the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the BCM through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.
Many of the electronic features in the vehicle controlled or supported by the BCM are programmable using a customer programming procedure or the DRBIII® scan tool. In addition, the BCM software is Flash compatible, which means it can be reprogrammed using Flash reprogramming procedures. However, if any of the BCM hardware components is damaged or faulty, the entire BCM unit must be replaced.