Diagnostics and testing of the charging system (Discovery 3)

General appearance

For information on the battery condition indicator, refer to Section 414-01, Battery and Wiring, of the Service Station Manual. When checking and charging the battery, refer to the instructions for the equipment used in the service station.

The generator is an intelligent system that can take into account temperature changes and optimize battery charging.

For a detailed description of the system construction and operation, refer to Section 414-02, Generator and Governor, in the Service Station Manual.

Inspection and verification

1. Check the customer complaint.

2. Visually inspect for obvious mechanical and electrical problems.

Mechanical elements	Electrical systems
Generator Drive belt Drive belt tensioner Generator pulley Check the reliability of the generator mounting	Generator Power supply element Starter Wiring harnesses and electrical connectors Fuses Battery Power Distribution Box (BJB) - Fuse Box 20E Starter Main Fuse Box Function of the charging indicator lamp CAN electrical circuits (Control Area Network) Engine Control Module (ECM)

3. If an obvious cause for the fault you have identified or the fault described by the customer is found, correct the fault before proceeding with further actions. (if possible).

4. Use an approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the symptom chart or DTC index.



Clear all DTCs after troubleshooting.

Table of signs of malfunction

Sign of malfunction	Possible reason	Actions taken
The charging indicator light does not light up	Lamp/circuit failure Generator failure CAN electrical circuit malfunction ECM failure	Check the operation of the test lamp with the ignition on and the engine off. Replace the lamps or repair the circuits as necessary. Check for diagnostic trouble codes (DTCs) indicating a faulty generator, CAN or ECM.
Charging indicator light is constantly on/battery is discharged	The auxiliary drive belt has broken Generator pulley slipping on shaft Malfunction generator Battery cable fault CAN electrical circuit malfunction ECM failure	Check battery and alternator cables. Refer to electrical manuals. Check for diagnostic trouble codes (DTCs) indicating alternator malfunction. Check accessory drive belt condition and tension. (see visual inspection table). Check that the pulley does not rotate independently of the alternator. Check for diagnostic trouble codes (DTCs) indicating a CAN or ECM fault.
Periodic switching on of the charging indicator lamp	Accessory drive belt slippage Battery cable fault Generator wiring fault Generator failure CAN electrical circuit malfunction	Check the condition of the accessory drive belt and its tension (see visual inspection table). Check battery and alternator cables. Refer to electrical manuals. Check for diagnostic trouble codes (DTCs) indicating alternator or CAN bus failure. Note that using a portable power supply or jump starter may cause the indicator light to remain on until the devices are disconnected.
The battery is discharged without the charging indicator light coming on	Battery failure Static discharge of the battery Open circuit in the generator circuit	Check battery condition, check battery for static discharge. Check for diagnostic trouble codes (DTCs) indicating alternator malfunction. Generator control circuit may be shorted to ground without setting DTCs. If no other discharge conditions are found, check this circuit. Refer to electrical manuals.
Noise (mechanical)	Accessory drive belt slippage Generator failure	Check the condition of the accessory drive belt and its tension (see visual inspection table). Disconnect the accessory drive belt and check that the generator rotates freely.

Table of fault codes

NOTE: Generic scan tools may not read the codes listed or may only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7-digit code to identify the fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

NOTE: For a complete listing of ECM DTCs, refer to Section 303-14, Electronic Engine Control System, in the service manual.

Diagnostic trouble code	Description	Possible reasons	Actions taken
P062200	Electrical circuit of the generator excitation winding terminal	Generator circuit failure Generator failure	Refer to the electrical manual and check the alternator electrical circuit. Repair/replace as necessary. Refer to the relevant section of the service station manual.
P062500	Low voltage in the generator excitation winding terminal circuit	Voltage sensing circuit: high resistance Generator B+ Circuit: Periodic High Resistance Generator Control Circuit Short to Ground	Check the charging circuit fuse. Check the charging voltage. Check the charging system electrical circuits. Refer to the electrical manuals. If no faults are found in the electrical circuits, install a new alternator. Refer to the appropriate section of the service manual. Clear the DTCs and check for proper operation.
P062600	High voltage in the generator excitation winding terminal circuit	Generator connector: loose/not connected Generator control circuit: short circuit to battery + Generator Control Circuit High Resistance	Check the charging voltage. Check the electrical circuits of the charging system. Refer to the electrical manuals. If no faults are found in the electrical circuits, install a new alternator. Refer to the appropriate section of the service manual. Clear the DTCs and check for proper operation.
P065B00	Generator Control Circuit Range/Performance Problems	Generator Control Circuit Short to Ground Generator control circuit: short circuit to battery + High resistance in the generator control circuit	Check the alternator and electrical circuits. Refer to electrical manuals. Repair/replace as necessary. Clear DTCs and check for proper operation.