Symptom Related Diagnostic Procedures

Battery Isolator Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The battery isolator is designed to protect the primary battery from excessive discharge while allowing the auxiliary battery to supply non-essential loads. When the Ignition switch is placed in the RUN position ignition voltage is supplied to the battery isolator. If the battery isolator detects the battery voltage drops below 12.2 Volts the battery isolator will open the auxiliary battery B+ circuit, separating the primary battery from the auxiliary battery and auxiliary circuits. If the battery voltage reaches 13.6 Volts the battery isolator will close the auxiliary battery B+ circuit, connecting the auxiliary battery to the primary battery and the charging system.

Reference Information

Schematic Reference

Auxiliary Battery Schematics Auxiliary Battery Schematics

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Description and Operation

Starting System Description and Operation Description and Operation

Electrical Information Reference

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Circuit Testing Circuit Testing

* Wiring Repairs Wiring Repairs

* Connector Repairs Connector Repairs

Circuit/System Testing

1. Verify that auxiliary fuse block and left rear body fuse block fusible links are not open.

• If either fusible link is open, test affected circuit for a short to ground.

2. Ignition OFF, disconnect L terminal connector at the battery isolator.

3. Verify a test lamp illuminates between the battery isolator harness side B+ circuit terminal L and ground.

• If the test lamp does not illuminate, repair the open/high resistance in the B+ circuit.

4. Verify a test lamp does not illuminate between the battery isolator component side B+ circuit terminal L and ground.

• If the test lamp illuminates, test the battery isolator ignition circuit for a short to voltage. If no short to voltage found, replace battery isolator.

5. Ignition OFF, disconnect X1 and P connector at the battery isolator.

6. Test for less than 2 ohms from the battery isolator harness side ground circuit B X1 and ground.

• If greater than 2 ohms, repair the short to voltage or open/high resistance in the circuit.

7. Verify a test lamp illuminates between the battery isolator harness side supply B+ circuit terminal P and ground.

• If the test lamp does not illuminate, test the battery isolator supply B+ circuit for an open/high resistance.

8. Engine running, verify a test lamp illuminates between the battery isolator harness side ignition circuit terminal A X1 and ground.

• If the test lamp does not illuminate, test the battery isolator ignition circuit an short to ground or open/high resistance.

9. Ignition OFF, connect X1 and P connector at the battery isolator.

10. Engine running, verify a test lamp illuminates between the battery isolator component side B+ circuit terminal L and ground.

• If the test lamp does not illuminate, replace the battery isolator.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Diagnostic Repair Verification Verification Tests

* Battery Isolator Replacement Battery Isolator Replacement