PRE-RELEASE
DTC U2105-U2199
| DTC U2105-U2199 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using the diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| DTC Descriptor |
Refer to Control Module U Code List .
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
| Module B+ | U2105-U2199 | U2105-U2199 | - | - |
| Ignition Voltage Circuits | U2105-U2199 | U2105-U2199 | - | - |
| Accessory Wake Up Serial Data | U1814 | U2105-U2199 | - | - |
| Serial Data Communication Enable | U2099 | U2105-U2199 | - | - |
| High Speed GMLAN Serial Data (+) | 2 | U2105-U2199 | 2 | - |
| High Speed GMLAN Serial Data (-) | 2 | U2105-U2199 | 2 | - |
| Low Speed GMLAN Serial Data | 1 | U2105-U2199 | 1 | - |
| Module Ground Circuits | - | U2105-U2199 | - | - |
| 1. Scan tool does not communicate with low speed GMLAN device 2. Scan tool does not communicate with high speed GMLAN device | ||||
| Circuit/System Description |
Control modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.
The body control module (BCM) activates the high speed GMLAN serial data wake up and the accessory wake up serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The high speed GMLAN serial data wake up circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory wake up serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM).
| Conditions for Running the DTC |
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System voltage is between 9-16 V.
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The vehicle power mode requires serial data communication to occur.
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| Conditions for Setting the DTC |
A supervised periodic message that includes the transmitter module availability has not been received.
| Action Taken When the DTC Sets |
The control module uses a default value for the missing parameters.
| Conditions for Clearing the DTC |
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A current DTC clears when the malfunction is no longer present.
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A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
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| Diagnostic Aids |
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If there are multiple non-communicating modules choose the one closest to the data link connector (DLC).
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During troubleshooting, you may note that a U-code was generated without there being any "active" status. U-codes for communication loss can be generated for a number of different reasons. They often produce no symptoms and remain undetected by the mechanic and troubleshooter. They will erase themselves automatically after a number of fault-free ignition cycles. Such conditions are likely caused by one of the following:
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A control module in the communication circuit was disconnected when the circuit was activated.
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Voltage to one or more control modules was interrupted during troubleshooting.
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A voltage drop in the battery caused certain control modules to stop communicating.
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Battery voltage was restored and certain control modules in the circuit were not reactivated simultaneously.
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If a U-code for loss of communication appears in the history with no apparent reason, it is likely due to one of the above scenarios. This is a temporary state and should not be interpreted as an intermittent fault with subsequent component replacement.
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A control module can have a U-code stored in the history without repair being required. 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.
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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.
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Use
Data Link References
to determine if the control module uses high or low speed GMLAN serial data communications
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Some control modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no control module output voltage circuit is shorted to ground before replacing the control module.
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Some intermittent communication problems can be caused by oxidation on the pins in the serial circuit. Inspect all connections to the control module that generated the communication DTC, the control module for which the communication DTC was set and cable connections between the two control modules. Do not replace a control module based only on oxidising corrosion. Refer to service bulletin 09-06-03-004 for help in troubleshooting and repairing this type of problem.
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This diagnostic can be used for any control module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that control module.
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| Reference Information |
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Data Communication Schematics
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Control Module References
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Connector End View Reference
Component Connector End Views
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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Scan Tool References
Control Module References for scan tool information
| Circuit/System Verification |
| 1. |
Determine which control module is not communicating. See
Control Module U Code List
.
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| 2. |
Verify that none of the following DTCs were generated: U0073, U2100, U0074, U0078, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, and P0562.
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| 3. |
If any of these DTCs has been generated, see
Diagnostic Trouble Code (DTC) List - Vehicle
.
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| Circuit/System Testing |
| Note | ||
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Pin and connector identifiers will be different depending on the individual control module being tested. Use Schematic Reference and Connector End View Reference to determine which connector/pin to access. |
| 1. |
Ignition OFF, disconnect the harness connector of the control module that is not communicating.
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| 2. |
Ignition OFF, test for less than 10 ohms between each ground circuit terminal and ground.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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Ignition ON, verify that a test lamp illuminates between each B+ pin and ground.
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If the lamp does not illuminate, test the B+ circuit for short to ground or open/high resistance. If a circuit fuse is open, check the control module's positive voltage outputs for short to ground. If the circuits test normal, replace the appropriate control module.
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Ignition ON, verify that a test lamp illuminates between each ignition voltage circuit terminal and ground.
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If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the control module for a short to ground. If the circuits test normal, replace the appropriate control module.
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Ignition ON, confirm that the test lamp illuminates between the circuit for serial data communication activation or the wake-up circuit pin to ground. |
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If the test lamp does not illuminate, test the entire circuit, including B+ to K9 of the BCM, for short to ground or open/high resistance. If the circuits test normal, replace the K9 body control module (BCM).
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Ignition OFF, disconnect the cable connections of the control module that generated the DTC.
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Ignition OFF, all doors closed, all vehicle systems OFF and all keys at least 3 metres from the vehicle. It can take up to 2 minutes for all vehicle systems to be de-energised. Test for less than 2 Ω on each GMLAN serial data circuit between the non-communicating control module and the control module that set the DTC.
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If greater than specified range, test the GMLAN serial data circuit for open/high resistance.
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If all circuits test normal, replace the control module that is not communicating.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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GMLAN Wiring Repairs
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Control Module References
for module replacement, setup, and programming
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