0866

0866-BATTERY VOLTAGE LOW

For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
The engine running. The engine speed greater than 1000 RPM.

- Set Condition:
Battery voltage is below 6 volts. Two Trip Fault.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. ACTIVE DTC
NOTE: Make sure the Battery is in good condition. Using the Midtronics Battery Tester, test the Battery before continuing.

NOTE: Inspect the vehicle for after market accessories that may exceed the Generator System output.

NOTE: Make sure the Generator drive belt is in good operating condition.

NOTE: Inspect the fuses in the IPM. If an open fuse is found, use the wire diagram/schematic as a guide, inspect the wiring and connectors for damage.

Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

Is the DTC Active or Pending at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

2. B+ CIRCUIT HIGH RESISTANCE
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

NOTE: Make sure all wires are clear of the engine's moving parts.

Measure the voltage between the B+ Terminal at the Generator and the Battery + Post.
Start the engine.
Is the voltage above 0.4 of a volt?

Yes

- Repair the excessive resistance in the B+ circuit between the Generator and Battery.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3

3. GENERATOR CASE GROUND HIGH RESISTANCE
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Ignition on, engine not running.
Start the engine.
Allow the engine to reach normal operating temperature.
Measure the voltage between the Generator case and Battery ground post.
Is the voltage above 0.1 of a volt?

Yes

- Repair excessive resistance in the Generator Ground between the Generator Case and Battery ground side.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

4. GENERATOR OPERATION
Turn the ignition off.
Disconnect the Generator Field harness connector.
Using a 12-volt test light connected to ground, probe the Generator Field Control circuit in the Generator Field harness connector.

NOTE: Make sure the test light is probing the circuit before actuating the Test or a DTC may set and not allow the actuation.

Ignition on, engine not running.
With the scan tool, actuate the Generator Field Control circuit.
Does the test light illuminate brightly and flash on and off?

Yes

- Replace the Generator.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5

5. GENERATOR FIELD CONTROL CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connector.
Measure the resistance of the Generator Field Control circuit from the Generator harness connector to the PCM.
Is the resistance below 5.0 ohms?

Yes

- Go To 6

No

- Repair the open in the Generator Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

6. GENERATOR FIELD CONTROL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the Generator Field Control circuit in the Generator Field harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the Generator Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 7

7. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test