COMPONENT LOCATION
DESCRIPTION
GENERAL DESCRIPTION

Malfunctions are detected using checksum techniques for verifying data.

Digital data is composed of zeros and ones. A checksum is the total of all ones in a string of data.

By comparing the checksum value with a stored value, a malfunction can be detected.

If an overrun occurs during normal operation, the microcontroller will be monitored when the following test conditions have been fulfiled :

1.

Ignition start has not occurred.

2.

Accelerator pedal not actuated.

3.

Cruise control is not active.

4.

No increase in external fuel quantity command.

DTC DESCRIPTION

If the ECM microcontroller generates threshold value, the ECM judged this as a fault and DTC is set.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible Cause

DTC Strategy

● Rationality check

●

Faulty ECM

Enable Conditions

● Ignition on

Threshold Value

● Case 1: microcontroller is reported as defective (recovery occurred (new program start))

● Case 2: injector is energized as engine while engine speed above 2050 rpm and APS is 0 % (fuel cut range)

● Case 3: engine speed has not dropped below 500 rpm within 1.5 sec. after turning the iginition switch off (Watchdog post-run test)

● Case 4: Gate array communication error occurs

Diagnostic Time

● Case 1: 0 sec.

● Case 2: AT 0.84 sec. MT 0.49 sec.

● Case 3: 0 sec.

● Case 4: 0.3 sec.

MIL

Fuel Limit

Fuel Cut

EGR Off

● No

● Yes (case3)

● Yes (case 1,2,4)

● No

MONITOR DTC STATUS
1.

Igintion " OFF ".

2.

Connect scantool and select Diagnostic Trouble Code(DTC).

3.

Clear DTC and then, Monitor DTC status.

4.

Is the DTC P1638 is retreived again ?

Substitute with a known-good ECM and check for proper operation.

If the problem is corrected, replace ECM and then go to "Verification of Vehicle Repair" 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, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

VERIFICATION OF VEHICLE REPAIR

After a repair, it is essential to verify that the fault has been corrected.

1.

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode and then clear DTC.

2.

Operate the vehicle within DTC Enable conditions in General information.

3.

Are any DTCs present ?

Go to the applicable troubleshooting procedure.

System is performing to specification at this time.

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