Intialization of the background test is the first one carried out in the system.
It therefore stsrts in the internal ROM and leads to supervisor identification by testing and initializing the external bus and testing the internal RAM.
Afterwards the external RAM is tested and the checksum of the EPROM is calculated.
After starting, A/D converter with all electric connections are monitored continuously by the ECM.
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.
DTC DESCRIPTION
If the ECM A/D converter 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: dynamic RAM test failure
● Case 2: APS 2 signal is above 200.39 mV when checking the ground connection every 2 second
● Case 3: sensor supply voltage is above 5.16 V or below 4.7 V
Diagnostic Time
● Case 1: 0.1 sec.
● Case 2: 0.5 sec.
● Case 3: 0.1 sec.
MIL
Fuel Limit
Fuel Cut
EGR Off
● No
● Yes
● No
● No
Fail Safe
● Engine speed is fixed at 1200 rpm without the accel position sensor action
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.
