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| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Refer to Control Module U Code List .
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Module B+ | U0100-U02FF | U0100-U02FF | -- | -- |
Module Ignition | U0100-U02FF | U0100-U02FF | -- | -- |
BCM Accessory Wake-up Serial Data | U1814 | U0100-U02FF | -- | -- |
BCM Serial Data Communication Enable | U2099 | U0100-U02FF | -- | -- |
Hybrid Powertrain Control Module 2 Accessory Wake-up Serial Data 2 | P06E4 | U0100-U02FF | -- | -- |
Hybrid Powertrain Control Module 2 High-Voltage Energy Management Communication Enable | P1EB9 | U0100-U02FF | -- | -- |
Low Speed GMLAN Serial Data | 1 | U0100-U02FF | 1 | -- |
High Speed GMLAN Serial Data (+) | 2 | U0100-U02FF | 2 | -- |
High Speed GMLAN Serial Data (-) | 2 | U0100-U02FF | 2 | -- |
Mid Speed GMLAN Serial Data (+) | 3 | U0100-U02FF | 3 | -- |
Mid Speed GMLAN Serial Data (-) | 3 | U0100-U02FF | 3 | -- |
Chassis High Speed GMLAN Serial Data (+) | U0077 | U0077, U0100-U02FF | U0077 | - |
Chassis High Speed GMLAN Serial Data (-) | U0077 | U0077, U0100-U02FF | U0077 | - |
Powertrain High-Speed GMLAN Serial Data (+) | U0074 | U0074, U0100-U02FF | U0074 | - |
Powertrain High-Speed GMLAN Serial Data (-) | U0074 | U0074, U0100-U02FF | U0074 | - |
High-Voltage Energy Management High Speed GMLAN Serial Data (+) | U007A | U007A, U0100-U02FF | U007A | - |
High-Voltage Energy Management High Speed GMLAN Serial Data (-) | U007A | U007A, U0100-U02FF | U007A | -- |
Module Ground | - | U0100-U02FF | -- | -- |
1. Scan Tool Does Not Communicate With Low-Speed GMLAN Device 2. Scan Tool Does Not Communicate With High-Speed GMLAN Device 3. Scan Tool Does Not Communicate With Mid-Speed GMLAN Device | ||||
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the data link connector (DLC) on the driver's side, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). The auxiliary data connector on the passenger side is used for expansion buses. When the vehicle is on, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the control module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.
The system voltage is between 9–16 V.
A supervised periodic message that includes the transmitter module availability has not been received.
| • | Specific subsystems will not function. |
| • | DTC U0100 in the TCM will cause the transmission to go into default gears. |
| • | Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate. |
| • | The ECM/TCM module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction. |
| • | 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 control module on the data communication circuit was disconnected while the communication circuit is awake. |
| - | Power to one or more control modules was interrupted during diagnosis. |
| - | A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold. |
| - | Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialise 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 control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code. |
| • | Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue. |
| • | Communication may be available between the control module and the scan tool with one or more GMLAN serial data systems inoperative. This condition is due to the control module using multiple GMLAN busses. |
| • | Use Data Link References to determine what GMLAN serial data communications the non communicating control module uses. |
| • | Some control modules 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 control module. |
| • | Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against and any in-line harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition.. |
| • | This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module. |
Data Link Communications Description and Operation
Control Module References for scan tool information
EL-48900 HEV Safety Kit
| ⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle . |
| ⇒ | If the DTC U0100-U02FF is set with symptom byte 00, refer to Circuit/System Testing. |
| ⇒ | If the DTC U0100-U02FF is set with symptom byte 71 or 72 along with other DTCs set, diagnose all other DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle . |
| ⇒ | If the DTC U0100-U02FF is set with symptom byte 71 or 72 and without other DTCs set, reprogram the control module. If the DTC resets, replace the control module. |
Danger: Always perform the High-Voltage Disabling procedure prior to servicing any High-Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.
The High-Voltage Disabling procedure will perform the following tasks:| • | Identify how to disable high-voltage. |
| • | Identify how to test for the presence of high-voltage. |
| • | Identify conditions under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed. |
| • | Safety glasses with appropriate side shields when within 15 metres (50 feet) of the vehicle, either indoors or outdoors. |
| • | Certified and up-to-date Class "0" Insulation gloves rated at 1,000 V with leather protectors. |
| - | Visually and functionally inspect the gloves before use. |
| - | Wear the Insulation gloves with leather protectors at all times when working with the high-voltage battery assembly, whether the system is energised or not. |
Note: Use the schematic to identify the following: • Control modules the vehicle is equipped with • Control module locations on each GMLAN serial data busses • The control module's B+, ignition, earth, accessory wake-up serial data, accessory wake-up serial data 2, serial data communication enable and serial data circuit terminals
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module. |
Note: Only the high-speed GMLAN modules have a serial data communication enable circuit OR an accessory wake-up serial data circuit OR an accessory wake-up serial data 2 circuit. Either the K9 BCM or the K114B hybrid powertrain control module 2 is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits and which control module is the output for these circuits.
| ⇒ | If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K9 BCM, for an open-circuit/high resistance or short-circuit to earth. If the circuits test normal, replace the K9 BCM. |
| ⇒ | If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K114B hybrid powertrain control module 2, for an open-circuit/high resistance or short-circuit to earth. If the circuits test normal, replace the K114B hybrid powertrain control module 2. |
Note: Only the high-voltage energy management high-speed GMLAN modules have a high-voltage energy management communication enable circuit and the K114B hybrid power train control module 2 is the output for this circuit. Refer to the control module schematics to identify which control modules have this circuit.
| ⇒ | If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the K114B hybrid powertrain control module 2, for an open-circuit/high resistance or short-circuit to earth. If the circuits test normal, replace the K114B hybrid powertrain control module 2. |
| • | X84 DLC low-speed GMLAN serial data circuit terminal 1 |
| • | X84 DLC high-speed GMLAN serial data circuit terminal 6 or 14 |
| • | X84 DLC mid-speed GMLAN serial data circuit terminal 3 or 11 |
| • | X84 DLC chassis high-speed GMLAN serial data circuit terminal 12 or 13 |
| • | X84B auxiliary data connector powertrain high-speed GMLAN serial data circuit terminal 12 or 13 |
| • | X84B auxiliary data connector high-voltage energy high-speed GMLAN serial data circuit terminal 3 or 11 |
| ⇒ | If greater than the specified range, test the serial data circuit for an open-circuit/high resistance between the non communicating control module and the control module setting the DTC or a serial data splice pack. |
Module | Voltage System | Data Link Type | ||||||
|---|---|---|---|---|---|---|---|---|
K16 Battery Energy Control Module (BECM) | 300 V 12 V |
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Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for control module replacement, programming and setup |
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