Diagnostic Overview - Smart Alternator

WARNING: This page is about a different variant/trim than selected.

PCM DIAGNOSTICS: When an electrical, mechanical or over-temp fault is detected and reported by the Smart Alternator to the PCM, the PCM sets a fault (P-code) and sends a default voltage set point of 14.0 volts to the Smart Alternator. Most vehicles will combine the failure modes into one fault code (P065A). However, some vehicles will separate each failure mode and set individual DTCs. It is important to note that on vehicles that use the combined P065A fault that this DTC can also set if the difference between the commanded set point and IBS voltage feedback are greater than a calibrated threshold. This means that the charging output should be checked before condemning an Alternator as faulty when a DTC is present.

When communication is lost between the PCM and Smart Alternator, the Smart Alternator will default to a voltage set point between 13.5 and 14.0 volts. The PCM will set a loss of communication fault (U-code) against the Smart Alternator. Besides an open or shorted LIN Bus circuit, the PCM can also lose communication with the Smart Alternator if the battery supply (open in the cable) or case ground to the Smart Alternator is lost. An open charging system fuse can cause a loss of battery supply to the Smart Alternator.

DIAGNOSTIC STRATEGY: Since the Smart Charging system does not always charge at idle, it is not unusual to see typical battery voltage present at the Smart Alternator stud during idling. Monitoring the voltage at the Smart Alternator stud at idle is not an effective way of checking the Smart Alternator output capability. This could lead to misdiagnosis and unnecessary replacement of the Smart Alternator. If it is suspected that the Smart Alternator is not charging to the level commanded by the PCM, a more effective way to determine this is to disconnect the LIN Bus circuit at the Smart Alternator and monitoring the voltage alternator stud. Disconnecting the communication line should cause the Smart Alternator to default to charging between approximately 13.5 and 14 volts. If the voltage does not increase to 13.5 to 14.0 volts at idle with the LIN Bus circuit open, the Smart Alternator is most likely faulty.

NOTE:

This method only applies to the Smart Alternators, not to the Electronic Voltage Regulation (EVR) charging systems with a standard Alternator. Standard Alternators are controlled directly by the PCM using a PWM voltage supply to energize the field.