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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 |
|---|---|---|---|---|
B+ | 1 | 1 | -- | -- |
Ignition | 1 | 1 | -- | -- |
Keyword 2000 Serial Data | 1 | 1 | 1 | -- |
Ground | -- | 1 | -- | -- |
1. Scan tool does not communicate with keyword 2000 device. | ||||
Modules connected to the serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.
The provisions for communicating with the engine control module (ECM), transaxle control module (TCM), immobiliser control module, and the remote keyless entry (RKE) /remote engine start (RES) module are located in the data link connector (DLC). The DLC is located under the instrument panel (I/P). The 16 pin DLC for the SIM2K-D52 application provides the serial data signals at terminals 7 (ECM, TCM, Immobiliser) and 8 (RKE, RES). The DLC is used to link a scan tool to the control module serial data circuit. Some common uses of the scan tool are listed below:
| • | Identifying stored diagnostic trouble codes (DTC) |
| • | Reading the serial data stream |
| • | Clearing DTCs |
| • | Reading stored Freeze Frame data |
| • | 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 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. |
| • | 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 some module and the scan tool with either the low/high speed GMLAN or the CAN serial data system inoperative. This condition is due to some modules using both GMLAN/CAN and KWP2000 systems. |
| • | An open in the DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle. When the scan tool attempts to communicate with the vehicle a message "no CANdi module detected" will be displayed. |
Data Link Communications Description and Operation
Control Module References for scan tool information
Note: Use the schematic to identify the following: • Control modules the vehicle is equipped with • Control module locations on the KWP2000 serial data circuit • The control modules B+, ignition, ground, 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. |
| • | DLC terminal 7 for ECM, TCM, and immobilizer unit |
| • | DLC terminal 8 for RKE/RES |
| ⇒ | If less than the specified range, test the serial data circuit for a short to ground. |
| • | DLC terminal 7 for ECM, TCM, and immobilizer unit |
| • | DLC terminal 8 for RKE/RES |
| ⇒ | If greater than the specified range, test the serial data circuit for a short to voltage. |
| • | DLC terminal 7 for ECM, TCM, and immobilizer unit |
| • | DLC terminal 8 for RKE/RES |
| ⇒ | If greater than the specified range, test the serial data circuit for open/high resistance. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for module replacement, setup, and programming.
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