2007 Liberty KJ Factory Service Manual 8 - ELECTRICAL

DIAGNOSIS AND TESTING

BATTERY SYSTEM

The battery, starting, and charging systems in the vehicle operate with one another and must be tested as a complete system. In order for the engine to start and the battery to maintain its charge properly, all of the components that are used in these systems must perform within specifications. It is important that the battery, starting, and charging systems be thoroughly tested and inspected any time a battery needs to be charged or replaced. The cause of abnormal battery discharge, overcharging or early battery failure must be diagnosed and corrected before a battery is replaced and before a vehicle is returned to service. The service information for these systems has been separated within this service manual to make it easier to locate the specific information you are seeking. However, when attempting to diagnose any of these systems, it is important that you keep their interdependency in mind.

The diagnostic procedures used for the battery, starting, and charging systems include the most basic conventional diagnostic methods, to the more sophisticated On-Board Diagnostics (OBD) built into the Powertrain Control Module (PCM). Use of an induction-type milliampere ammeter, a volt/ohmmeter, a battery charger, a carbon pile rheostat (load tester) and a 12-volt test lamp may be required. All OBD-sensed systems are monitored by the PCM. Each monitored circuit is assigned a Diagnostic Trouble Code (DTC). The PCM will store a DTC in electronic memory for any failure it detects. Refer to Charging System for the proper charging system on-board diagnostic test procedures.


MICRO 420 BATTERY TESTER

The Micro 420 automotive battery tester is designed to help the dealership technicians diagnose the cause of a defective battery. Follow the instruction manual supplied with the tester to properly diagnose a vehicle. If the instruction manual is not available refer to the standard procedure in this section, which includes the directions for using the Micro 420 battery tester.


BATTERY SYSTEM DIAGNOSIS
  
CONDITION
  		 POSSIBLE CAUSES
  		 CORRECTION
  
THE BATTERY SEEMS WEAK OR DEAD WHEN ATTEMPTING TO START THE ENGINE.
  

1. The electrical system ignition-off draw is excessive.

 

1. Refer to the IGNITION-OFF DRAW TEST Standard Procedure for the proper test procedures. Repair the excessive ignition-off draw, as required.

 

2. The charging system is faulty.

 

2. Determine if the charging system is performing to specifications. Refer to Charging System for additional charging system diagnosis and testing procedures. Repair the faulty charging system, as required.

 		  

3. The battery is discharged.

 

3. Determine the battery state-of-charge using the Micro 420 battery tester. Refer to the Standard Procedures in this section for additional test procedures. Charge the faulty battery, as required.

 		  

4. The battery terminal connections are loose or corroded.

 

4. Refer to Battery Cables for the proper battery cable diagnosis and testing procedures. Clean and tighten the battery terminal connections, as required.

 		  

5. The battery has an incorrect size or rating for this vehicle.

 

5. Refer to Battery System Specifications for the proper size and rating. Replace an incorrect battery, as required.

 		  

6. The battery is faulty.

 

6. Determine the battery cranking capacity using the Micro 420 battery tester. Refer to the Standard Procedures in this section for additional test procedures. Replace the faulty battery, as required.

 		  

7. The starting system is faulty.

 

7. Determine if the starting system is performing to specifications. Refer to Starting System for the proper starting system diagnosis and testing procedures. Repair the faulty starting system, as required.

 		  

8. The battery is physically damaged.

 

8. Inspect the battery for loose terminal posts or a cracked and leaking case. Replace the damaged battery, as required.

 		  
THE BATTERY STATE OF CHARGE CANNOT BE MAINTAINED.
  

1. The battery has an incorrect size or rating for this vehicle.

 

1. Refer to Battery System Specifications for the proper specifications. Replace an incorrect battery, as required.

 

2. The battery terminal connections are loose or corroded.

 

2. Refer to Battery Cable for the proper cable diagnosis and testing procedures. Clean and tighten the battery terminal connections, as required.

 		  

3. The electrical system ignition-off draw is excessive.

 

3. Refer to the IGNITION-OFF DRAW TEST Standard Procedure for the proper test procedures. Repair the faulty electrical system, as required.

 		  

4. The battery is faulty.

 

4. Test the battery using the Micro 420 battery tester. Refer to Standard Procedures for additional test procedures. Replace the faulty battery, as required.

 		  

5. The starting system is faulty.

 

5. Determine if the starting system is performing to specifications. Refer to Starting System for the proper starting system diagnosis and testing procedures. Repair the faulty starting system, as required.

 		  

6. The charging system is faulty.

 

6. Determine if the charging system is performing to specifications. Refer to Charging System for additional charging system diagnosis and testing procedures. Repair the faulty charging system, as required.

 		  

7. Electrical loads exceed the output of the charging system.

 

7. Inspect the vehicle for aftermarket electrical equipment which might cause excessive electrical loads.

 		  

8. Slow driving or prolonged idling with high-amperage draw systems in use.

 

8. Advise the vehicle operator, as required.

 		  
THE BATTERY WILL NOT ACCEPT A CHARGE.
  		 1. The battery is faulty.
  		 1. Test the battery using the Micro 420 battery tester. Charge or replace the faulty battery, as required.
  


ABNORMAL BATTERY DISCHARGING

Any of the following conditions can result in abnormal battery discharging:

  • A faulty or incorrect charging system component. Refer to Charging System for additional charging system diagnosis and testing procedures.
  • A faulty or incorrect battery. Use Micro 420 battery tester and refer to Battery System for additional battery diagnosis and testing procedures.
  • A faulty circuit or component causing excessive ignition-off draw.
  • Electrical loads that exceed the output of the charging system. This can be due to equipment installed after manufacture, or repeated short trip use.
  • A faulty or incorrect starting system component. Refer to Starting System for the proper starting system diagnosis and testing procedures.
  • Corroded or loose battery posts and/or terminal clamps.
  • Slow driving speeds (heavy traffic conditions) or prolonged idling, with high-amperage draw systems in use.