P0620 Alternator Control Circuit - Automotive Repair Guides & Equipment

COMPONENT LOCATION

GENERAL DESCRIPTION

The alternator is duty controlled as current control by ECM with the battery voltage, current, temperature information from battery sensor. The more electrical load, the higher duty output.

DTC DESCRIPTION

If it is open or short in COM circuit of alternator. ECM sets DTC.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

Voltage monitoring

1.	Poor connection

2.	Open or short in circuit

3.	Faulty PCM

Enable Conditions

Case1

Engine running

Case2

Igintion ON

Threshold value

Case1

Alternator COM line shorted ground or power

Case2

Alternator COM line open

Diagnosis Time

5 sec

MIL On Condition

DTC only (NO MIL ON)

DIAGNOSTIC CIRCUIT DIAGRAM

SIGNAL WAVEFORM & DATA

Fig.1) Normal waveforms of COM, FR terminal of alternator at idle.

Fig.2) Normal waveforms of COM, FR terminal of alternator under high electronic load condition.

Fig.3) Normal waveforms of COM, FR terminal of alternator at ig on under connector disconnected condition.

Fig.4) Normal waveforms of COM, FR terminal of alternator at idle under connector disconnected condition.

MONITOR GDS DATA

1.	Connect GDS to Data Link Connector(DLC).

IG “ON”.

3.	Select “DTC” button, and then Press “DTC Status” to check DTC’s information from the DTCs menu.

4.	Read “DTC Status” parameter.

Is parameter displayed “Present fault”?

	▶ Go to “Terminal and Connector inspection” procedure.
	▶ Fault is intermittent caused by poor contact in the sensor’s and/or ECM’s connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary

TERMINAL AND CONNECTOR INSPECTION

1.	Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage..

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary and go to “Verification of Vehicle Repair” procedure
	▶ Go to ” Control Circuit Inspection ” procedure.

CONTROL CIRCUIT INSPECTION

■ Check waveform

1.	IG “OFF” and connect scantool.

2.	Connect probe to COM terminal to check control waveform by using oscilloscope function.

ENG “ON” and monitor signal waveform.

Signal waveform will be displayed as Signal Waveform & Data.

Is the measured waveform within specification ?

	▶ Go to “Check Open in harness” as follows.
	▶ Go to “Check Short in harness” as follows.

■ Check Open in harness

1.	IG “OFF” and disconnect Alternator and PCM connector

Measure resistant between com terminal of alternator and PCM harness connector.

Below 1Ω

Is the measured resistance within specification ?

▶ Substitute with a known – good ECM and check for proper operation. If the problem is corrected, replace ECM and go to “Verification of Vehicle Repair” procedure.

There is a memory reset function on scantool that can erase optional parts automaticallydetected and memorized by ECM. Before or after testing ECM on the vehicle, use this function to reuse the ECM on the others

▶ Repair open in harness and go to “Verification of Vehicle Repair” procedure .

■ Check Short in harness

1.	IG “OFF” and disconnect Alternator and PCM connector

2.	Measure the resistance between com terminal of the alternator harness connector and chassis ground.

IG “ON” and measure the valtage between com terminal of the alternator harness connector and chassis ground.

Approx. below 1Ω, Approx. 0V

Is the measured resistance and voltage within specification ?

▶ Substitute with a known – good ECM and check for proper operation. If the problem is corrected, replace ECM and go to “Verification of Vehicle Repair” procedure.

There is a memory reset function on GDS that can erase optional parts automatically detected and memorized by ECM. Before or after testing ECM on the vehicle, use this function to reuse the ECM on the others.

▶ Repair short in harness

New Videos on our YouTube Channel Every Week, Subscribe Now!

Related Posts