U Code Charts
U0001General Description
Several control units are applied to electronically controlled vehicles. These units perform each control with information's 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, ABS, ESP)
As sharing signals of engine speed, APS, gear shifting, torque reduction in ESP, ABS and various modules, active control is performed.
DTC Description
Checking CAN communication. Under detecting condition, if an output signal 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:
Schematic Diagram:
Signal Waveform
Signal Waveform:
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 2.5 V, Check if current cam signal transfers correctly.
Continuous "0" signal above 6BIT means the occurrence 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.
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 BUS resistance
1. Ignition "OFF".
2. Measure the resistance between terminals 41 and 42 of PCM harness connector. (Test 1)
3. Disconnect PCM connector and ABS (or ESP) control module connector.
4. Measure the resistance between terminals 41 and 42 of PCM harness connector. (Test 2)
Specification:
- PCM and ABS (or ESP) connected: 60 ± 3 ohms (Test 1)
- PCM and ABS (or ESP) 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) control module connector.
3. Check continuity between terminal 41 of PCM harness connector and chassis ground. (CAN HIGH line)
4. Check continuity between terminal 42 of PCM harness connector and chassis ground. (CAN LOW line)
Specification: Discontinuity (Infinite ohms)
5. Is 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) control module connector.
3. Ignition "ON"
4. Check the voltage between terminal 41 of PCM harness connector and chassis ground. (CAN HIGH line)
5. Check the voltage between terminal 42 of PCM harness connector and chassis ground. (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)
4. Check continuity in CAN LOW line. (CAN LOW: PCM connector terminal 42, ABS connector terminal 15, ESP connector terminal 14)
Specification: Continuity (below 1.0 ohms)
5. Is the measured resistance within the specification?
YES - Go to "Component Inspection" procedure.
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 terminal 41 (CAN HIGH) and 42 (CAN LOW) of PCM harness connector respectively.
3. Ignition "ON" after connecting only PCM to CAN BUS.
4. Ignition "ON" after connecting only ABS or ESP control 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 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. 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 readiness 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.