GM Service Manual Online
For 1990-2009 cars only

Special Tools

J 42000 Batter Tester

Diagnostic Aids

Important: 

   • A dead battery is usually a symptom of another problem. Repair the problem. Do not just charge or replace the battery.
   • Failure to properly understand the battery and its function could lead to a misdiagnosis and unneeded repairs. Refer to Battery Description and Operation and Battery Common Causes of Malfunction for more information.

Follow these instructions in order to avoid an incorrect diagnosis because of connections:

    • If testing the vehicle with the battery cables still connected, wiggling the clips on the J 42000 terminal. This may cut through any coating or through any oxidation that may be present on the terminal.
    • If correct connections to the battery terminal bolts in the vehicle are in doubt, perform the following steps:
        1. Disconnect the negative battery cable.
        2. Disconnect the positive battery cable.
    • If the tester displays a "Bad Battery" result for a battery tested in the vehicle with the battery cables connected, perform the following steps:
        1. Disconnect the negative battery cable.
        2. Disconnect the positive battery cable.
        3. Replace the battery only if the Out-of-Vehicle test shows a "Bad Battery" result. This prevents battery replacements that are due only to faulty battery cable connections.

Circuit/System Testing

Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Inspect the battery for a cracked, broken, or damaged case, which may be indicated by battery acid leakage.
  2. If there is any apparent damage, replace the battery.
  3. Verify the cold cranking amperage (CCA), and reserve capacity (RC) and/or amp hour (AH) rating of the battery to the original battery or original equipment (OE) specification. Refer to Battery Usage.
  4. If the battery does not meet or exceed specifications, replace the battery.
  5. Verify that the battery cables are clean and tight. The battery terminal bolts should be torqued as specified in Fastener Tightening Specifications.
  6. If the battery cable(s) need to be cleaned, clean as required and tighten as specified.
    If the battery cable(s) are damaged, replace then tighten as specified.
  7. Install the J 42000 and follow directions supplied by the tester.
  8. If the tester calls for charging the battery, refer to Battery Charging.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Battery Positive Cable Replacement
    •  Battery Negative Cable Replacement
    •  Battery Replacement