Diagnostic Aids
- The battery test using the J 42000 Battery Tester requires correct connections to the battery terminals. See Special Tools . A failure to obtain the correct connections during the test may result in a failed test on a good battery.
- Use the Out of Vehicle test for each battery when testing a vehicle with dual batteries.
Follow these instructions in order to avoid an incorrect diagnosis because of connections:
- If testing the vehicle with the battery cables still connected, wiggle the J 42000
clips on the terminal bolt. See Special Tools . This may cut through any coating or through any oxidation that may be present on the bolt.
Even new bolts contain a protective coating that may insulate or cause a resistance in the test circuit.
- If correct connections to the battery terminal bolts in the vehicle are in doubt, perform the following steps:
- Disconnect the negative battery cable.
- Disconnect the positive battery cable.
- Install the test adapters on the terminals.
- Follow the instructions for testing a removed battery.
- If the tester displays a REPLACE BATTERY or BAD CELL-REPLACE result for a battery tested in the vehicle with the battery cables connected, perform the following steps:
- Disconnect the negative battery cable.
- Disconnect the positive battery cable.
- Install the tester adapters.
- Follow the instructions for testing a removed battery.
- Replace the battery only if the second test shows a REPLACE BATTERY or BAD CELL-REPLACE result.
Use the test code from the second test for any warranty purposes.
IMPORTANT: Always write the test code displayed by the tester on the repair order for any warranty purposes. The number is a unique code that describes the test data for a particular battery at a particular time. The test code may occasionally repeat when you retest the same battery. More often, each test will result in a different code. Use the test code from the second, or Out of Vehicle test. - Use the correct terminal adapters.
Do not use any common bolts or a combination of bolts, of nuts, and of washers as adapters when testing the battery.
Use the test adapters that are provided with the J 42000 or GM P/N 12303040 terminal adapters. See Special Tools . If the adapters that are provided with the J 42000 require replacement, use GM P/N 12303040. See Special Tools . Any other adapter may not contact the correct areas of the battery terminal, causing a resistance that may result in an invalid battery test result.