P0641 Sensor Reference Voltage ‘A’ Circuit/Open

COMPONENT LOCATION

GENERAL DESCRIPTION

The ECM provides a 5 volt reference voltage to Throttle Position Sensor 1(TPS1). The ECM monitors reference voltage deviation from the power supply circuit of the sensors.

DTC DESCRIPTION

Checking the voltage from sensor power supply every 1.87 sec. under detecting condition, if the value within detecting condition lasts for more than 0.2 sec., ECM sets P0641.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

Sensor reference voltage check

1.	Short in sensor power supply line

2.	Faulty ECM

Enable Conditions

IG “ON”

Threshold value

Sensor supply power < 4.5V or > 5.5V

Diagnosis Time

Continuous (More than 0.2 seconds failure for every 1.87 seconds test )

MIL On Condition

3 driving cycle

DIAGNOSTIC CIRCUIT DIAGRAM

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

1.	IG “OFF” and disconnect ETC Motor & TPS connector.

IG “ON”

Measure voltage between TPS power terminal of ETC Motor & TPS harness connector and chassis ground.

Approx. 5V

Is the measured voltage within specification ?

	▶ Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair as necessary and go to “Verification of Vehicle Repair” procedure.
	▶ Go to “Check short in power harness” as follows.

■ Check short in power harness

1.	IG “OFF” and disconnect ETC Motor & TPS connector and ECM connector.

2.	Measure the resistance between TPS power and ETC motor (+) terminals of ETC Motor & TPS harness connector.(Measurement “A”)

3.	Measure the resistance between TPS power and ETC motor (-) terminals of ETC Motor & TPS harness connector.(Measurement “A”)

Measure the resistance between TPS power and TPS ground terminals of ETC Motor & TPS harness connector.(Measurement “B”)

Infinite

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.

▶ Repair short in power harness

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