U Code Charts
DTC U0001 CAN COMMUNICATION MALFUNCTIONGENERAL DESCRIPTION
Several control units are applied to electronically controlled vehicles. These units perform each control with informations from various sensors. Thus, sharing signal information from sensors is needed, so CAN communication type whose communication speed is high and insensitive to electrical noise by spark generation is adopted to controlling power-train(PCM, ASS, ESP)As sharing signals of engine speed, APS, gear shifting, torque reduction in ESp,ASS and various modules, active control is performed.
DTC DESCRIPTION
Checking CAN communication, under detecting condition, if an error within the detecting condition is detected for more than 1.5 sec., PCM sets U0001. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition:
Specification:
Signal Waveform And Data:
TERMINAL AND CONNECTOR INSPECTION
1. Electrical systems consist of a lot of harness and connectors, poor connection of terminals can cause various problems and damage of component.
2. Perform checking procedure as follows.
1. Check damage of harness and terminals: Check terminals for contact resistance, corrosion and deformation.
2. Check connecting condition of PCM and component connector: Check terminal separation, damage of locking device and connecting condition between terminal and wiring.
NOTE: Disconnect the pin which requires checking at male connector and insert it to the terminal at female connector for checking connecting condition. (after checking, reconnect the pin at correct position.)
3. Is the problem found?
YES :Repair the trouble causing part and go to "Verification of Vehicle Repair".
NO :Go to "Signal Circuit Inspection".
SIGNAL CIRCUIT INSPECTION
1. Check CAN BUS resistance in Data Link Connector
1 Ignition "OFF".
2 Measure the resistance between terminals 3 and 11 of data link connector (Test 1)
3 Disconnect PCM connector.
4. Measure the resistance between terminals 3 and 11 of data link connector (Test 2)
Specification :
PCM and ABS(or ESP) module connected: 60 ± 3 Ohms (Test 1)
PCM and ABS(or ESP) module disconnected: 120 ± 3 Ohms (Test 2)
5. Is CAN BUS resistance within the specification?
YES :Go to "2.Check short to ground in CAN BUS" as follows.
NO :
- Below 10 Ohms for both conditions(disconnected, connected) : Repair short between CAN BUS lines and go to "Verification of Vehicle Repair".
- 120 Ohms for both conditions(disconnected, connected) : Go to "4. Check CAN BUS continuity".
- Infinite Ohms for both conditions(disconnected, connected) :Repair open in CAN communication circuit between DLC terminal and In-panel junction box.
2. Check short to ground in CAN BUS
1. Ignition "OFF"
2. Disconnect PCM and ABS(or ESP) module connector.
3. Check continuity between DLC terminal 3 and chassis ground. (CAN HIGH line)
4. Check continuity between DLC terminal 11 and chassis ground. (CAN LOW line)
Specification : Discontinuity (Infinite Ohms)
5. Is the measured resistance within the specification?
YES :Go to "3. Check short to battery in CAN BUS".
NO :Repair short to ground in circuit and go to "Verification of Vehicle Repair".
3. Check short to battery in CAN BUS
1. Ignition "OFF"
2. Disconnect PCM and ABS(or ESP) module connector.
3. Ignition "ON"
4. Measure the voltage of DLC terminal 3. (CAN HIGH line)
5. Measure the voltage of DLC terminal 11. (CAN LOW line)
Specification: 0.0 V - 0.1 V
6. Is the measured voltage within the specification?
YES :Go to"4. Check CAN BUS continuity" as follows.
NO :Repair short to battery and go to "Verification of Vehicle Repair".
4. Check CAN BUS continuity
1. Ignition "OFF"
2. Disconnect PCM and ABS(or ESP) module connector.
3. Check continuity in CAN HIGH line.
(CAN HIGH: PCM connector terminal 41, ABS connector terminal 26, ESP connector terminal 35, Data link connector(DLC) terminal 3)
4. Check continuity CAN LOW line.
(CAN LOW: PCM connector terminal 42, ABS connector terminal 15, ESP connector terminal 14, Data link connector(DLC) terminal 11)
Specification : Continuity (below 1.0 Ohms)
5. Is the measured resistance within the specification?
YES :Go to "Component Inspection".
NO :Repair open in CAN BUS line and go to "Verification of Vehicle Repair".
COMPONENT INSPECTION
1. Check CAN communication waveform generation
1. Ignition "OFF"
2 Connect 2 channel scope to DLC terminal 3(CAN HIGH) and 11(CAN LOW) respectively.
3 Ignition "ON" after connecting only PCM to CAN BUS.
4 Ignition "ON" after connecting only ABS or ESP module to CAN BUS
Specification: At Ignition "ON", the waveform same as "Signal Waveform & Data" of above signal waveform. * Different from "Signal Waveform & Data", if 1) both CAN HIGH and LOW signal are fixed at 2.5 V or 2) HIGH and LOW signal are fixed at 3.5 V and 1.5 V, respectively, it is due to communication error between modules.
5. Does correct waveform generate from each module?
YES :Go to "Verification of Vehicle Repair".
NO :Replace the module which generates poor communication waveform, and go to "Verification of Vehicle Repair".
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. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3. Read "DTC Status" parameter
4. Is parameter displayed "History(Not Present) fault"?
YES :System performing to specification at this time. Clear the DTC
NO :Go to the applicable troubleshooting procedure.