DTC U0100-U02FF (Using Digital Multimeter)

Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor For device DTC descriptors, refer to Control Module U Code List. For symptom byte information, refer to Symptom Byte List. Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
B+	U0100-U02FF	U0100-U02FF	—	—
Ignition	U0100-U02FF	U0100-U02FF	—	—
CAN 1 Serial Data [+] (circuit 4987)	U0075*	U0100-U02FF	U0075*	—
CAN 1 Serial Data [-] (circuit 4986)	U0075*	U0100-U02FF	U0075*	—
CAN 2 Serial Data [+] (circuit 4979)	U0073*	U0100-U02FF	U0073*	—
CAN 2 Serial Data [-] (circuit 4978)	U0073*	U0100-U02FF	U0073*	—
CAN 3 Serial Data [+] (circuit 4977)	U0074*	U0100-U02FF	U0074*	—
CAN 3 Serial Data [-] (circuit 4976)	U0074*	U0100-U02FF	U0074*	—
CAN 4 Serial Data [+] (circuit 4101)	U0079*	U0100-U02FF	U0079*	—
CAN 4 Serial Data [-] (circuit 4100)	U0079*	U0100-U02FF	U0079*	—
CAN 5 Serial Data [+] (circuit 4985)	U007B*	U0100-U02FF	U007B*	—
CAN 5 Serial Data [-] (circuit 4984)	U007B*	U0100-U02FF	U007B*	—
CAN 8 Serial Data [+] (circuit 4105)	U007E*	U0100-U02FF	U007E*	—
CAN 8 Serial Data [-] (circuit 4104)	U007E*	U0100-U02FF	U007E*	—
LIN Serial Data	U0100-U02FF	U0100-U02FF	U0100-U02FF	—
Ground	—	U0100-U02FF	—	—
* Other DTCs may set with this fault.

Circuit/System Description The serial data circuit is the means by which the devices in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the X84 Data Link Connector (DLC), the scan tool can be used to monitor each device for diagnostic purposes and to check for Diagnostic Trouble Codes (DTC). Each device communicating on the serial data circuit sends data to each other. When a device stops communicating on the serial data circuit, for example if the device loses power or ground, the data it normally sends on the serial data circuit disappears. Other devices on the serial data circuit, which expect to receive that data, detect its absence; those devices in turn set a DTC associated with the loss of data of the non-communicating device. The DTC is unique to the device which is not communicating and one or more devices may set the same exact code. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored code. Conditions for Running the DTC The system voltage is between 9-16 V. Serial data communication is active. Conditions for Setting the DTC A supervised periodic message has not been received for specified period of time depending on the rate of message. Action Taken When the DTC Sets Specific subsystems will not function. Conditions for Clearing the DTC A current DTC will change to history status when the diagnostic runs and passes. A history DTC will clear after 40-100 consecutive malfunction-free ignition cycles depending on the device. Diagnostic Aids Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U code present. However, there is no associated “current” or “active” status. Loss of communication U codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios: – A device on the data communication circuit was disconnected while the communication circuit is awake. – Power to one or more devices was interrupted during diagnosis. – A low battery condition was present, so some devices stop communicating when battery voltage drops below a certain threshold. – Battery power was restored to the vehicle and devices on the communication circuit did not all re- initialize at the same time. – If a loss of communication U code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part. A device may have a U code stored in history that does not require any repairs. Issues with late or corrupted messages between devices can be temporary with no apparent symptom or complaint; this does not mean the device is faulty. Do not replace a device based only on a history U code. Do not replace a device reporting a U code. The U code identifies which device needs to be diagnosed for a communication issue. Use Data Link References to determine what serial data communications the device uses. Some devices may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the device. Reference Information Schematic Reference Data Communication Schematics Control Module References Connector End View Reference Master Electrical Component List Description and Operation Data Link Communications Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

Note

For vehicles not equipped with K29F Front Seat Heater Control Module, K29FV Front Seat Heater Vent Control Module, K29R Rear Seat Heater Control Module, or K32 Heated Steering Wheel Module: – Ignore DTC U0208 if equipped with RPO 00V – Ignore DTC U0229 if equipped with RPO 00G – Ignore DTC U0247 if equipped with RPO 00R

1. Ignition ON/Vehicle In Service Mode.
2. Verify DTC U300D, P2534, P2535, U0073-U007E, or U100B is not set. ⇒ If any of the DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If none of the DTCs are set
3. Determine the device that is not communicating. Refer to Control Module U Code List.
4. Refer to Data Link References to determine which data communication bus the non communicating device is on.
5. Verify DTC U0100-U02FF is not set. ⇒ If the DTC is set and the non communicating device is on one of the CAN buses Refer to Circuit/System Testing — Testing a CAN Device. ⇒ If the DTC is set and the non communicating device is on one of the LIN buses Refer to Circuit/System Testing — Testing a LIN Device. ⇓ If the DTC is not set
6. A fault is currently not present and may be an intermittent condition. Circuit/System Testing

Note

Use the schematics and connector end views to identify the device’s ground, B+, ignition, and serial data circuit terminals. Testing a CAN Device

1. Ignition ON/Vehicle In Service Mode.
2. Verify the CAN device is not communicating. ⇒ If the device is still communicating 2.1. Ignition/Vehicle OFF, disconnect all the harness connectors at the CAN device specified by the DTC descriptor. 2.2. Ignition ON/Vehicle In Service Mode, refer to step 8 to diagnose a fault in the serial data circuits. ⇓ If the device is not communicating
3. Ignition/Vehicle OFF, disconnect all the harness connectors at the CAN device that is not communicating.
4. Verify a test lamp illuminates between each of the ground circuit terminals and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance in the ground circuit or ground connection. ⇓ If the test lamp illuminates
5. Ignition ON/Vehicle In Service Mode.
6. If equipped, verify a test lamp illuminates between each of the B+ circuit terminals and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 6.1. Test for an open/high resistance in the B+ circuit. ⇒ If an open/high resistance is found, repair the fault in the circuit. ⇓ If an open/high resistance is not found 6.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 6.1. Test for a short to ground in the B+ circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 6.2. Replace the disconnected device. ⇓ If the test lamp illuminates
7. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, which has a fuse in the circuit, and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 7.1. Test for an open/high resistance in the ignition circuit. ⇒ If an open/high resistance is found, repair the fault in the circuit. ⇓ If an open/high resistance is not found 7.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 7.1. Test for a short to ground in the ignition circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 7.2. Replace the disconnected device. ⇓ If the test lamp illuminates
8. Test for less than 4.5 V between each of the CAN Bus serial data circuit terminals and ground. ⇒ If 4.5 V or greater between a CAN Bus 1 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 1 to test for a short to voltage. ⇒ If 4.5 V or greater between a CAN Bus 2 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 2 to test for a short to voltage. ⇒ If 4.5 V or greater between a CAN Bus 3 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 3 to test for a short to voltage. ⇒ If 4.5 V or greater between a CAN Bus 4 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 4 to test for a short to voltage. ⇒ If 4.5 V or greater between a CAN Bus 5 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 5 to test for a short to voltage. ⇒ If 4.5 V or greater between a CAN Bus 8 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 8 to test for a short to voltage. ⇓ If less than 4.5 V
9. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
10. Test for greater than 100 Ω between each of the CAN Bus serial data circuit terminals and ground. ⇒ If 100 Ω or less between a CAN Bus 1 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 1 to test for a short to ground. ⇒ If 100 Ω or less between a CAN Bus 2 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 2 to test for a short to ground. ⇒ If 100 Ω or less between a CAN Bus 3 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 3 to test for a short to ground. ⇒ If 100 Ω or less between a CAN Bus 4 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 4 to test for a short to ground. ⇒ If 100 Ω or less between a CAN Bus 5 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 5 to test for a short to ground. ⇒ If 100 Ω or less between a CAN Bus 8 serial data circuit and ground Refer to Scan Tool Does Not Communicate with Device on CAN 8 to test for a short to ground. ⇓ If greater than 100 Ω
11. Test for less than infinite resistance between each of the CAN Bus serial data circuit terminals and ground. ⇒ If infinite resistance Repair the open/high resistance in the serial data circuit. ⇓ If less than infinite resistance

Note

The following test step is only applicable to a CAN device with 2 pairs of serial data circuits or a CAN device with an internal terminating resistor.

12. Test for 110-130 Ω between each pair of the CAN Bus serial data circuits. ⇒ If less than 110 Ω Refer to an appropriate diagnostic procedure below to test for a short between the serial data circuits. Scan Tool Does Not Communicate with Device on CAN 1 Scan Tool Does Not Communicate with Device on CAN 2 Scan Tool Does Not Communicate with Device on CAN 3 Scan Tool Does Not Communicate with Device on CAN 4 Scan Tool Does Not Communicate with Device on CAN 5 Scan Tool Does Not Communicate with Device on CAN 8 ⇒ If greater than 130 Ω Refer to an appropriate diagnostic procedure below to test for an open/high resistance in the serial data circuit. Scan Tool Does Not Communicate with Device on CAN 1 Scan Tool Does Not Communicate with Device on CAN 2 Scan Tool Does Not Communicate with Device on CAN 3 Scan Tool Does Not Communicate with Device on CAN 4 Scan Tool Does Not Communicate with Device on CAN 5 Scan Tool Does Not Communicate with Device on CAN 8 ⇓ If between 110-130 Ω
13. Inspect both harness and component connectors for contamination, corrosion, and terminal tension.
14. Reconnect the harness connectors at the CAN device.
15. Ignition ON/Vehicle In Service Mode.
16. Verify the DTC is not set again. ⇒ If the DTC is set Replace the device that is not communicating. ⇓ If the DTC is not set
17. A fault is currently not present and may be an intermittent condition. Testing a LIN Device
18. Ignition/Vehicle OFF, disconnect all the harness connectors at a LIN device that is not communicating.
19. Verify a test lamp illuminates between each of the ground circuit terminals and B+. ⇒ If the test lamp does not illuminate Repair the open/high resistance in the ground circuit or ground connection. ⇓ If the test lamp illuminates
20. Ignition ON/Vehicle In Service Mode.
21. If equipped, verify a test lamp illuminates between each of the B+ circuit terminals and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 4.1. Test for an open/high resistance in the B+ circuit. ⇒ If an open/high resistance is found, repair the fault in the circuit. ⇓ If an open/high resistance is not found 4.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 4.1. Test for a short to ground in the B+ circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 4.2. Replace the disconnected device. ⇓ If the test lamp illuminates
22. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, which has a fuse in the circuit, and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 5.1. Test for an open/high resistance in the ignition circuit. ⇒ If an open/high resistance is found, repair the fault in the circuit. ⇓ If an open/high resistance is not found 5.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 5.1. Test for a short to ground in the ignition circuit. ⇒ If a short to ground is found, repair the fault in the circuit. ⇓ If a short to ground is not found 5.2. Replace the disconnected device. ⇓ If the test lamp illuminates
23. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, which is controlled by a control module, and ground. ⇒ If the test lamp does not illuminate 6.1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the control module that controls the ignition circuit and all devices that share the same ignition circuit. 6.2. Test for infinite resistance between the ignition circuit and ground. ⇒ If less than infinite resistance, repair the short to ground in the circuit. ⇓ If infinite resistance 6.3. Test for less than 2 Ω in the ignition circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇓ If less than 2 Ω 6.4. Reconnect the control module that controls the ignition circuit. 6.5. Ignition ON/Vehicle In Service Mode. 6.6. Verify a test lamp illuminates between the ignition circuit terminal and ground. ⇒ If the test lamp does not illuminate, replace the control module that controls the ignition circuit. ⇓ If the test lamp illuminates 6.7. Ignition/Vehicle OFF, reconnect the first device that shares the same ignition circuit. 6.8. Ignition ON/Vehicle In Service Mode. 6.9. Verify a test lamp illuminates between the ignition circuit terminal and ground. ⇒ If the test lamp does not illuminate, replace the device that was just connected. ⇒ If the test lamp illuminates and there are more devices to connect, connect the next device and repeat step 6.9 until there are no more devices to connect. ⇓ If the test lamp illuminates
24. Ignition/Vehicle OFF, disconnect all LIN devices that share the same LIN serial data circuit.
25. Ignition ON/Vehicle In Service Mode.

Note

For accurate voltage reading, disconnect the battery charger prior to performing the following test step.

9. Test for 3.5-12 V between the LIN serial data circuit terminal and ground. ⇒ If less than 3.5 V 9.1. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC. 9.2. Test for infinite resistance between the LIN serial data circuit terminal and ground. ⇒ If less than infinite resistance, repair the short to ground in the circuit. ⇓ If infinite resistance 9.3. Test for less than 2 Ω in the LIN serial data circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇓ If less than 2 Ω 9.4. Replace the control module that sets the DTC. ⇒ If greater than 12 V 9.1. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC. 9.2. Ignition ON/Vehicle In Service Mode. 9.3. Test for less than 1 V between the LIN serial data circuit terminal and ground. ⇒ If 1 V or greater, repair the short to voltage in the circuit. ⇓ If less than 1 V 9.4. Replace the control module that sets the DTC. ⇓ If between 3.5-12 V
10. Verify how many LIN devices are connected to this LIN circuit. ⇒ If there is only one LIN device 10.1. Ignition/Vehicle OFF, inspect both harness and component connectors for contamination, corrosion, and terminal tension. 10.2. Reconnect the harness connectors at the LIN device. Verify all connectors/terminals are fully seated. 10.3. Ignition ON/Vehicle In Service Mode. 10.4. Verify the DTC is not set again. ⇒ If the DTC is set, replace the LIN device that is not communicating. ⇓ If the DTC is not set 10.5. A fault is currently not present and may be an intermittent condition. ⇓ If there are two or more LIN devices
11. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC.
12. Reconnect the harness connectors at the first LIN device.
13. Ignition ON/Vehicle In Service Mode.
14. Test for 3.5-12 V between the LIN serial data circuit terminal at the control module setting the DTC and ground. ⇒ If less than 3.5 V or greater than 12 V Replace the LIN device that was just connected. ⇓ If between 3.5-12 V
15. Ignition/Vehicle OFF, reconnect the harness connectors at another LIN device.
16. Ignition ON/Vehicle In Service Mode.
17. Test for 3.5-12 V between the LIN serial data circuit terminal at the control module setting the DTC and ground. ⇒ If less than 3.5 V or greater than 12 V Replace the LIN device that was just connected. ⇓ If between 3.5-12 V
18. Repeat steps 15-17 for the remaining LIN devices until a faulty LIN device is identified. If there is no faulty LIN device, replace the LIN device that is not communicating. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification. For control module replacement, programming, and setup, refer to: Control Module References