Tech 2 Cannot Communicate with GM-LAN Modules - kw 3.5 3.6 4.6 Candi communication connector control no crank start data diagnostics driveability DTC gauge hard hesitate idle inoperative LH2 LY7 LX9

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

The Tech 2 cannot communicate with GM-LAN Modules.

The following information will help you with communication issues:

1. Ensure that the dealer does not have a 10 mb memory card installed in their Tech 2, only the 32 mb card.
2. Verify that the LED does flash on their CANdi module. Refer to step 11 for further information.
3. The CTS and SRX class2 message monitor should include the ECM/PCM, even though it is on a GMLAN data bus.

-	You cannot pull DTC, Review any data, or SPS program the PCM without the Candi module connected, or if the CAN/LAN data lines are open/shorted, on the CTS and SRX. If the class 2 lines are shorted this will NOT effect retrieving data or DTCs from the ECM/TCM.

-	The PCM is always active on class 2 message monitor until it loses the battery feed from the ECM/TCM fuse. Pulling any other fuse will not affect its activity on the class 2 message monitor. This is true for the CTS and SRX

-	The IPC and VTD also go inactive when pulling the PCM/TCM fuse on the SRX

-	You cannot review any data or request info for SPS programming without having the CANdi module connected. We are using the LAN data line for programming.

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The Malibu will request info for programming without the Candi module connected, and review some engine data. Only the PCM would come on the class 2 monitor but after 4 seconds go inactive, you can ping the module and it will come on again and then go inactive. Cycling the key has no effect and the power moding check also has no response when cycling the key.

4. The Tech 2 has a new diagnostic feature called functional diagnosis under special functions. Verify the CANdi module communication with ECM/PCM. The green L.E.D. flashes one time per second when it is working properly.
5. Always use the latest version software for the Tech 2.
6. Verify that the Tech 2 data cable between the Tech 2 and the DLC is not the concern, for no communication with the ECM/PCM.
7. Only use the 16 pin DLC connector with the molded connector with the bridge between the row of pins.
8. The field has been calling in product reports on defective CANdi modules.
9. Refer to the appropriate SI document for the scan tool does not communicate with high-speed GM-LAN device.
10. Refer to the appropriate SI document for the DLC schematics.
11. Check the LED indicator on the CANdi module to see how fast it is flashing. If it is flashing slowly (1 time per 3 seconds) then there is a problem between the Tech 2 and CANdi module. If the indicator is flashing fast (1 time per second), it is more likely that they are having a vehicle problem with GM-LAN.
12. Next step is this work around method for Tech 2.

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Select TOOL OPTIONS

Select PROGRAMMING TECH 2

Select RESET TECH 2 (soft key)

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Tech 2 does a "warm reboot" back to main screen. Take another look at the CANdi LED indicator. If now flashing fast then likely it will communicate with the vehicle. However this reset procedure probably has to be repeated each time you turn on Tech 2.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

(2004 Cadillac CTS) and (2004 Cadillac SRX ) and (2004 Cadillac XLR) and (2004 Chevrolet Malibu)

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