Engine Control
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, ESC, 4WD ECM)As sharing signals of engine speed, APS, gear shifting, torque reduction in ESP, ESC 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:
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 2 V - at BUS IDLE state (DIGITAL "1") whose reference voltage is 2.5 V, "0" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5V, Check if current cam signal transfers correctly. Continuous "0"signal above 6BIT means the occurence of error in CAN communication. 1BIT is easily distinguished as calculating the time when "SOF" (START OF FRAME) which notifies the start of frame occurs. Check if "0"signal above 6BIT is detected continuously when monitoring CAN communication waveform.
MONITOR DTC STATUS
1. Check DTC Status
1. Connect scantool to Data Link Connector (DLC).
2. IG "ON".
3. Select "Diagnostic Trouble Codes (DTCs)" mode, and then Press F4 (DTAL) to check DTC's information from the DTCs menu
4. Read "DTC Status" parameter.
5. Is parameter displayed "Present fault"?
YES -Go to "Terminal and connector inspection" procedure.
NO - 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, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
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
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 ESC connected : 60 ± 3 ohms (Test 1)
PCM and ESC 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 tines and go to "Verification of Vehicle Repair".
- 120 ohms for both conditions (disconnected, connected): Go to "4. Check CAN BUS continuity".
- Infinite ohm 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 ESC 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 ohm)
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 ESC 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 ESC connector.
3. Check continuity in CAN HIGH line.
(CAN HIGH : PCM connector terminal 41, ESC connector terminal 35, Data link connector (DLC) terminal 3)
4. Check continuity CAN LOW line.
(CAN LOW : PCM connector terminal 42, ESC connector terminal 14, Data link connector (DLC) terminal 11)
Specification : Continuity (below 1.0 ohm)
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
1. Ignition "OFF"
2. Connect 2 channel scope to DLC terminal 3 (CAN HIGH) and 11 (CAN LOW).
3. Ignition "ON" after connecting only PCM to CAN BUS.
4. Ignition "ON" after connecting only ESC 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.