Diagnostic Test
- 1) ACTIVE DTC NOTE: Inspect the vehicle for aftermarket accessories that may exceed the Generator System output.
Ignition on, engine not running.
NOTE: The battery must be fully charged.NOTE: The Generator belt tension and condition must be checked before continuing.With a scan tool, read DTCs.
With a scan tool, erase DTCs.
Start the engine.
Allow the idle to stabilize.
With the scan tool, read DTCs.
Is the DTC active at this time?
Yes
- Go To 2).
No
- Refer to the INTERMITTENT CONDITION diagnostic procedure.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
- 2) FUSED B+ CIRCUIT HIGH RESISTANCE NOTE: Inspect the Generator harness connector and the Generator Eyelet for corrosion or damage before continuing.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.
NOTE: Make sure all wires are clear of the engine's moving parts.Measure the voltage between the Generator B+ Output Terminal and the Battery (+) Post.
Start the engine.
Is the voltage above 0.1 of a volt?
Yes
- Repair the excessive resistance in the battery positive circuit between the Generator and Battery.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Go To 3).
- 3) EXCESSIVE RESISTANCE IN THE CASE GROUND 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.
Start the engine.
Warm the engine to operating temperature.
NOTE: Make sure all wires are clear of the engine's moving parts.Measure the voltage between the Generator Case and Battery ground post.
Is the voltage above 0.1 of a volt?
Yes
- Repair the excessive resistance in the Generator Case Ground.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Go To 4).
- 4) (A803/A804) GEN SENSE CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.Measure the voltage of the (A803/A804) Gen Sense circuit in the appropriate terminal of special tool #8815.
Is the voltage equal to Battery voltage?
Yes
- Go To 5).
No
- Check the (A803/A804) Gen Sense Circuit for an open. If OK, replace the Generator in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
- 5) GENERATOR OPERATION
Turn the ignition off.
Disconnect the Generator Field harness connector.
Using a 12-volt test light connected to ground, probe the Gen Field Control circuit in the Generator Field harness connector.
Ignition on, engine not running.
With a scan tool, actuate the Generator Field Driver.
Does the test light illuminate brightly and flash on and off?
Yes
- Replace the Generator.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Go To 6).
- 6) (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (K20) Gen Field Control circuit in the Generator Field harness connector.
Is the voltage above 1.0 volt?
Yes
- Repair the short to battery voltage in the (K20) Gen Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Go To 7).
- 7) (K20) FIELD CONTROL CIRCUIT OPEN
Turn the ignition off.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.Measure the resistance of the (K20) Gen Field Control circuit from the Generator Field harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Yes
- Go To 8).
No
- Repair the open in the (K20) Gen Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
- 8) (K20) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUND
Courtesy of DAIMLERCHRYSLER CORP.
Measure the resistance between ground and the (K20) Gen Field Control circuit in the Generator Field harness connector.
Is the resistance below 100 ohms?
Yes
- Repair the short to ground in the (K20) Gen Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Go To 9).
- 9) 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. (Refer to POWERTRAIN VERIFICATION TEST)
No
- Replace and program the Powertrain Control Module per Service Information. Refer to MODULE-POWERTRAIN CONTROL and STANDARD PROCEDURE - PCM/ECM/SKREEM PROGRAMMING .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to POWERTRAIN VERIFICATION TEST)