2.0L SULEV
U0001Component Location:
General Description
A communication line exists between the Engine Control Module (ECM) and the Transaxle Control Module (TCM). The communication is through a Control Area Network (CAN). Without CAN communication, an independent pin and wiring is needed to receive a sensor information from a ECM. The more information to be communicated, the more wirings is required. In case of CAN communication type, all the information need to be communicated among control modules such as ECM and ABS control module use CAN lines.
DTC Description
The ECM determines CAN communication error and sets DTC U0001 if communication with other control devices (e.g. ABS) via CAN is impossible or ECM detects that communication time via CAN exceeds threshold value.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform:
Monitor DTC Status
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode
2. Press F4(DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
4. Read "DTC Status" parameter
5. Is parameter displayed "History (Not Present) fault"?
CAUTION:
- History (Not Present) fault : DTC occurred but has been cleared.
- Present fault : DTC is occurring at present time.
YES
a. Fault is intermittent caused by poor contact in the sensor's and/or the ECM's connector, which was repaired but ECM 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
a. Go to next step as below
Check CAN Communication Line for Open
1. Ignition "OFF"
2. Disconnect ECM harness connector
3. Measure resistance between terminals 77 and 78 of the ECM harness connector.
Specification : Approx. 110 - 130 ohms
4. Is resistance within the specification?
YES
a. Go to next step as below
NO
a. Check for open in wiring related to the CAN communication (ECM, EPS, MTS and vertical resistor at the junction box). Repair as necessary and then go to "Verification of Vehicle Repair" procedure
CAUTION: Vertical Resistor Resistance : Approx. 110 - 130 ohms
Check CAN Communication Line for Short to Ground
5. Measure resistance between terminal 77 of the ECM harness connector and chassis ground.
6. Measure resistance between terminal 78 of the ECM harness connector and chassis ground.
Specification : infinity (above 10 kohms)
7. Is resistance within the specification?
YES
a. Go to next step as below
NO
a. Repair CAN communication line for a short to ground. And then go to "Verification of Vehicle Repair" procedure
Check CAN Communication Line for Short to Battery
8. Disconnect the connectors related to the CAN communication
9. Ignition "ON" & Engine "OFF"
10. Measure voltage between terminal 77 of the ECM harness connector and chassis ground.
11. Measure voltage between terminal 78 of the ECM harness connector and chassis ground.
Specification : Approx. 0 V
12. Is voltage within the specification?
YES
a. Go to next step as below
NO
a. Repair CAN communication line for a short to battery. And then go to "Verification of Vehicle Repair" procedure
Terminal and Connector Inspection
1. Many malfunctions in the electrical system are caused by poor harness(es) 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
a. Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO
a. Go to next step as below
Component Inspection
1. Ignition "OFF"
2. Measure resistance between terminals 77 and 78 of the ECM connector (ECM side)
Specification : Approx. 110 - 130 ohms
3. Is resistance within the specification?
YES
a. Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO
a. Check ECM for contamination, deterioration, or damage. Substitute with a known-good ECM and check for proper operation. If the problem is corrected, replace ECM and then go to "Verification of Vehicle Repair" procedure.
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
a. System performing to specification at this time. Clear the DTC
NO
a. Go to the applicable troubleshooting procedure.