Captiva |
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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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Module B+ | U2105-U2199 | U2105-U2199 | -- | -- |
Module Ignition | U2105-U2199 | U2105-U2199 | -- | -- |
Accessory Wake Up Serial Data | U1814 | U2105-U2199 | -- | -- |
High Speed GMLAN Serial Data Wake Up | 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 | - | U2105-U2199 | -- | -- |
1. Scan Tool Does Not Communicate with Low Speed GMLAN Device 2. Scan Tool Does Not Communicate with High Speed GMLAN Device | ||||
Modules connected to the high GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The 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 system voltage is between 9–16 V. |
| • | The vehicle power mode master requires serial data communication to occur. |
A supervised periodic message that includes the transmitter module availability has not been received.
The modules is never signalled, therefore the specific subsystems will not function.
| • | A current DTC clears when the malfunction is no longer present. |
| • | A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction. |
| • | Use the DTC Descriptor list above to determine the module which is not communicating. |
| • | If there are multiple non-communicating modules choose the one closest to the data link connector (DLC). |
| • | Use Data Link References to determine if the module uses high or low speed GMLAN serial data communications. |
| • | Some 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 module output voltage circuit is shorted to ground before replacing the module. |
| • | This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module. |
| ⇒ | 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, also test the positive voltage outputs 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, also test the positive voltage outputs 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 wakeup serial data circuit, and the BCM is the output for these circuits. Refer to the control module schematics to identify which modules have these circuits.
| ⇒ | If the test lamp does not illuminate, test the entire circuit, including the B+ circuit to the BCM, for an open/high resistance or a short to ground. If the circuits test normal, replace the BCM. |
| • | Class 2 serial data circuit terminal 2 |
| • | Low speed GMLAN serial data terminal 1 |
| • | High speed GMLAN serial data terminal 6 or 14 |
| ⇒ | If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a module setting the DTC or a serial data splice pack. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for module replacement, programming and setup |
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