U Code Charts
DTC U0001 CAN COMMUNICATION MALFUNCTIONGENERAL 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, adtive control is performed.
DTC DESCRIPTION
Checking CAN communication every 1 sec. under detecting condition, if an output signal within the detecting condition is detected for more than 1.5 sec. PCM sets U0001. MIL(Malfunction Indicating Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Specification:
Schematic Diagram:
Signal Waveform And Data:
SIGNAL WAVEFORM AND DATA
Monitoring CAN HIGH and LOW simultaneously is important in monitoring CAN communication waveform When CAN HIGH signal rise to 3.5 V and LOW signal drops to 1.5 V - voltage difference between HIGH and LOW signal is 2V - at BUS IDLE state (DIGITAL "1") whose reference voltage is 2.5 V, "O" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5 V, Check if current CAM signal is transfers correctly.
Continuous "O"signal above 6BIT means the occurence of error in CAN communication. 1 BIT is easily distinguished as calculating the time when "SOF"(START OF FRAME) which notifies the start of frame occurs. Check it "O"signal above 6BIT is detected continuously when monitoring CAN communication waveform.
MONITOR SCANTOOL DATA
1. Connect Scantool to Data Link Connector (DLC).
2. Warm engine up to normal operating temperature.
3. Turn "OFF" electrical devices and A/C.
4. Monitor the data from PCM through CAN communication among ABSCM or ESP data
If CAN is normal, vehicle speed data is showed through CAN communication line from ABS or ESP control module.
5. Is the data displayed correctly?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and 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 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.
3. Has a problem been found?
YES: Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO: Go to "Signal Circuit Inspection" procedure.
SIGNAL CIRCUIT INSPECTION
1. Check CAN communication bus resistance
1. Ignition "OFF".
2. Check connection state of PCM connector(C144-1) and ESP or ABS connector(E22)
3. Measure the resistance between ESP or ABS connector 15 and 26 refering to the checking condition of specification as follows.
Specification
- PCM connector, ESP or ABS connector connected : 60 ohms ± 5 ohms
- PCM connector disconnected, ESP or ABS connector connected : 120 ohms ± 10 ohms
- PCM connector connected, ESP or ABS connector disconnected : 120 ohms ± 10 ohms
4. Is CAN BUS resistance within the specification?
YES: Go to "Check short to ground in CAN BUS" as follows.
NO:
When resistance is about 1.0 Ohms Go to "3. Check short between CAN communication lines" as follows
When resistance is infinite Ohm Go to "4. Check open in CAN communication line" as follows
2. Check short to ground in CAN communication bus
1. Ignition "OFF"
2. Disconnect ESP or ABS connector.
3. Measure resistance between terminal 26 of ESP or ABS harness connector and chassis ground.
Specification : Infinite
4. Is the measured resistance within the specification?
YES: Go to "Component Inspection" procedure
NO:
Below 1.0 Ohms is detected: Repair short to ground in CAN High circuit and go to "Verification of Vehicle Repair" procedure.
Above 120 ohmsd is detected: Repair short to ground in CAN Low circuit and go to "verification of Vehicle Repair" procedure.
3. Check short between CAN communication lines(LOW and HIGH)
1. Ignition "OFF"
2. Disconnect PCM connector and ESP or ABS connector.
3. Measure resistance between terminal 15 and 26 of ESP or ABS harness connector.
Specification : Infinite
4. Is the measured resistance within the specification?
YES: Go to "Component Inspection" procedure.
NO: Below 1.0 Ohms is detected Repair short between CAN LOW and HIGH signal line and go to "Verification of Vehicle Repair" procedure.
4. Check open in CAN communication line
1. Ignition "OFF".
2. Disconnect PCM connector and ESP or ABS connector.
3. Measure resistance between terminal 42/C144-1 of PCM harness connector and terminal 15 of ABS or EPS harness connector.(CAN Low)
4. Measure resistance between terminal 41/C144-1 of PCM harness connector and terminal 26 of ABS or EPS harness connector (CAN hi)
specification : Below 1.0 Ohms
5. Is the measured resistance within the specification?
YES: Go to "Component Inspection" procedure.
NO: Repair open in harness and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check the resistance of CAN BUS inside of module
1. Ignition "OFF"
2. Measure the resistance between ABS or ESP connector 15 and 26 refering to the checking condition of specification as follows.
Specification :
- PCM connector disconnected, ESP or ABS connector connected. (TEST "A"): 120 ohms ± 10 ohmss
- PCM connector connected, ESP or ABS connector disconnected (TEST "B"): 120 ohms ± 10 ohmss
3. Is the measured resistance within the specification?
YES: Go to "2. Check CAN communication waveform" as follows
NO:
TEST "A" problem: the resistance of CAN BUS inside of ABS or ESP is without specification. Replace ABS or ESP and go to "Verification of Vehicle Repair"
TEST "B" problem: the resistance of CAN BUS inside of PCM is without specification. Replace PCM and go to "Verification of Vehicle Repair"
2. Check CAN communication waveform output
1. Ignition "OFF"
2. Connect 2 channel scope to ABS or ESP connector terminal 15 and 26.
3. Disconnect ABS or ESP connector and check CAN communication waveform after Ignition "ON". (TEST "A")
4. Disconnect PCM connector and check CAN communication waveform after Ignition "ON". (TEST "B")
Specification : Communication waveform similar to the waveform of "Signal Waveform & Data" is displayed when Ignition "ON"
- It means communication error of connected module when, being different from reference waveform, 1. CAN HIGH and LOW signals are fixed at 2.5 V or 2.HIGH and LOW signals are fixed at 3.5 V and 1.5 V,respectively
5. Does correct waveform generate from ECM and TCM?
YES: Go to "Verification of Vehicle Repair"
NO:
TEST "A" waveform is abnormal: Replace PCM due to the communication error with PCM and go to "Verification of Vehicle Repair"
TEST "B" waveform is abnormal: Replace ABS or ESP due to the communication error with ABS or ESP and go to "Verification of Vehicle Repair"
Repeat this process 2-3 times.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions
4. Monitor that all rediness test have been verified as" Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.