P0622 Volvo Generator Field Not Switching

Possible causes

– Battery charge
– Faulty Generator
– Generator harness is open or shorted
– Generator circuit poor electrical connection
– Engine Control Module (ECM) controlled generator
– Faulty ECM

Tech description

If the battery is OK then the alternator is more than likely the problem.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0622 Volvo Description

The Engine Control Module (ECM) uses the generator turn on signal circuit to control the generator. A high side driver within the ECM allows the ECM to turn the generator ON and OFF. When Generator operation is desired, the ECM sends a 5 volt signal to the voltage regulator via the generator turn on signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the Generator is enabled by the ECM, the voltage regulator controls generator output independently of the ECM. Under certain operating conditions, the ECM can turn Off the generator by turning Off the 5 volt signal on the generator turn on signal circuit.