P0562 System Voltage Low - Automotive Diagnosis

COMPONENT LOCATION

GENERAL DESCRIPTION

The ECM monitors battery voltage while the engine is running. The ECM looks at voltage fed to the ECM from the Main Relay.

DTC DESCRIPTION

During engine running, if system voltage is below 11V or the battery power input line has a problem, ECM sets P0562.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

Voltage too low

1.	Poor connection

2.	Open or short in circuit

3.	Faulty charging system

4.	Faulty main relay

5.	Faulty ECM

Enable Conditions

Case1

Engine works

Case2

–

Threshold value

Case1

System voltage < 11V

Case2

Open or short to ground in memory power line

Diagnosis Time

Case1

Continuous

Case2

Continuous (More than 5 sec.failure for every 10 sec.test)

MIL On Condition

3 driving cycle

SPECIFICATION

Coil Resistance

70Ω ~ 120Ω

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.

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 ” Power Circuit Inspection ” procedure.

POWER CIRCUIT INSPECTION

■ Check voltage (main relay)

1.	IG “OFF” and disconnect the main relay.

IG “ON”

Measure the voltage between power supply terminals of main relay harness connector and chassis ground.

Specification : Approx. B+

Is the measured voltage within specification ?

	▶ Go to “Check voltage (memory power)” as follows.
	▶ Check the fuse between battery and main relay. ▶ Repair open or short to ground in power harness and go to “Verification of Vehicle Repair” procedure .

■ Check voltage (memory power)

1.	IG “OFF” and disconnect ECM connector

IG “ON”

Measure voltage between memory power terminal of ECM harness connector and chassis ground

Specification : Approx. B+

Is the measured voltage within specification ?

	▶ Go to “Check open in harness” as follows.
	▶ Check for open or short to ground in harness. ▶ Check whether fuse is installed or blown off. ▶ Repair or replace as necessary and then, go to “Verification of Vehicle Repair”procedure.

■ Check open in harness

1.	IG “OFF” and disconnect the main relay and ECM connector.

Measure the resistance between main relay ‘ON’ power terminal of main relay harness connector and main relay ‘ON’ power terminals of ECM harness connector.

Specification : Approx. below 1Ω

Is the measured resistance within specification ?

	▶ Go to “Check short to ground in harness” procedure.
	▶ Repair open in harness and go to “Verification of Vehicle Repair” procedure.

■ Check short to ground in harness

1.	IG “OFF” and disconnect the main relay and ECM connector.

Measure the resistance between main relay ‘ON’ power terminal of main relay harness connector and chassis ground.

Specification : Infinite

Is the measured resistance within specification ?

	▶ Go to “Control Circuit Inspection” procedure.
	▶ Repair short to ground in harness and go to “Verification of Vehicle Repair” procedure.

CONTROL CIRCUIT INSPECTION

■ Check short to ground in harness

1.	IG “OFF” and disconnect the main relay and ECM connector.

Measure the resistance between control terminal of main relay harness connector and chasses ground.

Specification : Infinite

Is the measured resistance within specification ?

	▶ Go to “Check open in harness” procedure.
	▶ Repair short to ground in control harness and go to “Verification of Vehicle Repair” procedure.

■ Check open in harness

1.	IG “OFF” and disconnect the main relay and ECM connector.

Measure the resistance between control terminal of main relay harness connector and main relay control terminal of ECM harness connector.

Specification : Approx. below 1Ω

Is the measured resistance within specification ?

	▶ Go to “System Inspection” procedure.
	▶ Repair open in control harness

SYSTEM INSPECTION

■ Check Generator circuit

1.	Engine starts.

2.	Maintain ENG RPM 2,500RPM over 2 minutes.

Measure voltage between the battery terminal(+) and the battery terminal(-).

Approx. 12.5 ~ 14.7V

Is the measured voltage within specification?

	▶ Go to “Component Inspection” procedure.
	▶ Check that the tension of drive belt, ENG RPM, fuse, terminal of battery, all terminals of generator are in good condition and Check for damaged harness and poor connection between generator and battery. If OK repair or replace generator

COMPONENT INSPECTION

■ Check Main relay

1.	IG “OFF” and disconnect main relay.

2.	Measure the resistance between battery power supply and control terminals of main relay.(Measurement “A”)

Measure the resistance between battery power supply and power supply to ECM terminals of main relay.(Measurement “B”)

Specification :

Terminal	Continuity
Battery power supply – Power supply to ECM	NO
Battery power supply – Main relay control	YES(Approx. 70Ω ~ 120Ω)

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 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.

▶ Substitute with a known – good Fuel Pump Relay and check for proper operation. If the problem is corrected, replace Fuel Pump Relay

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