Computers and Control
DTC U0001 CAN COMMUNICATION BUSGENERAL DESCRIPTION
As vehicles electronically controlled, various control unit is applied to vehicle and several units are controlled based on the signals from the sensors. Therefore sharing signals of sensors and information is required. To meet this requirement, CAN communication type, which is insensible to external noises and whose communication speed is fast, is applied to power train control.
Sharing signals from RPM, APS, gear shifting, torque reduction in ESP, ABS and various modules, addtive control is performed.
DTC DESCRIPTION
If it is impossible to communicate through internal or external CAN line over 500 ms, ECM/PCM sets DTC U0001.
DTC Detecting Condition:
Signal Waveform & Data:
MONITOR SCANTOOL DATA
1. Connect scantool to Data Link Connector (DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "CAN" parameters on the scantool.
- Check the value of current data displayed normally.
- Check "Transaxle Range Switch" and "Torque Required from TCU" parameters among ECU'S current data. (AT vehicle only)
- Check "TPS", "RPM", and "Idle Status" parameters among TCU's current data. (AT vehicle only)
- Check "RPM" and "TPS" parameters among ABS's current data. (ABS or ESP vehicle only)
4. Are the parameters displayed correctly?
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM/PCM's connector or was repaired and ECM/PCM 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.
NO - Go to "Terminal and connector Inspection" procedure.
TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminal condition. 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.
3. Has a problem been found?
YES - Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO - Go to "CAN communication Circuit Inspection" procedure.
SIGNAL CIRCUIT INSPECTION
PCM A/T:
ECM M/T:
1. Check CAN BUS Short to Ground.
1. Key "OFF".
2. Disconnect ECM/PCM connector.
3. Measure the resistance between terminal 12 of ECM/PCM harness connector and chassis ground. [A/T]
Measure the resistance between terminal 84 of ECM/PCM harness connector and chassis ground. [M/T]
4. Measure the resistance between terminal 27 of ECM/PCM harness connector and chassis ground. [A/T]
Measure the resistance between terminal 62 of ECM/PCM harness connector and chassis ground. [M/T]
Specification : Infinite
5. Is the measured resistance within specification?
YES - Go to "CAN BUS Terminus Resistance Check (Harness side)" procedure.
NO - Repair Short in signal circuit and then go to "Verification of Vehicle Repair" procedure.
PCM A/T:
ECM M/T:
2. CAN BUS Terminus Resistance Check (Harness side)
1. Key "OFF".
2. Disconnect ECM/PCM connector.
3. Measure the resistance between terminal 12 and 27 of ECM/PCM harness connector. [A/T]
Measure the resistance between terminal 84 and 62 of ECM/PCM harness connector. [M/T]
Specification : 120 ± 10 Ohms
4. Is the measured resistance within specification?
YES - Go to "Component Inspection" procedure.
NO
- In case the measured resistance is around 1.0 Ohm : Repair Short in signal circuit and then go to "Verification of Vehicle Repair" procedure.
- In case the measured resistance is Infinite : Repair Open in signal circuit and then go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
PCM A/T:
ECM M/T:
1. CAN BUS Terminus Resistance Check (Component side)
1. Key "OFF".
2. Disconnect ECM/PCM connector.
3. Measure the resistance between terminal 12 and 27 of ECM/PCM connector. (Component side)
Measure the resistance between terminal 84 and 62 of ECM/PCM connector. (Component side)
Specification : 120 ± 10 Ohms
4. Is the measured resistance within specification?
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM/PCM's connector or was repaired and ECM/PCM 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.
NO
- Substitute with a known - good ECM/PCM and check for proper operation.
- If the problem is corrected, replace ECM/PCM and go to "Verification of Vehicle Repair" procedure.
NOTE: There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by ECM/PCM. Before or after testing ECM/PCM on the vehicle, use this function to reuse the ECM/PCM
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.
2. Clear the DTCs and Operate the vehicle within DTC Enable conditions in General information.
3. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure.
NO - System is performing to specification at this time.