Data Link Connector Diagnosis

Diagnostic Chart:

Description:

CIRCUIT DESCRIPTION

The diagnostic tables in Transmission Control Systems are, by design, for use with a scan tool. If the scan tool is inoperative, correct the scan tool before beginning any other diagnostic procedures. If the Data Link Connector (DLC) powers the scan tool, DLC Pin 16 provides the B+ power. DLC Pin 4 provides the ground for the scan tool's power supply. DLC Pin 5 is an additional ground for serial data. Serial data for Powertrain diagnostics is on DLC Pin 7.

TEST DESCRIPTION

The number(s) below refer to the step number(s) on the Diagnostic Table.

2. If the ground circuit on DLC pin 4 opens after the scan tool is up and running, the screen will go blank but the scan tool may remain on. If there is no ground at pin 4 initially, the scan tool will not power up.

9. Some of the older scan tools receive power through a separate power cord from the cigar lighter. If you use this type of scan tool, and the tool will not power up, check the lighter socket for damage or a poor connection. Refer to Engine Electrical Cigar Lighter for circuit details.

13. If there is no communication between the Transmission Control Module (TCM) and the scan tool, no data will be displayed. Serial Data is disrupted when the system voltage is below 9.0 Volts or above 16.0 Volts. A scan tool will not display the data if the system voltage is outside of this range. If no data is displayed with the engine running, but the data is displayed with the ignition on, engine off, high system voltage (overcharging) may be at fault. If this is the case, the scan tool should display DTC P0560 System Voltage with the ignition on and the engine off.

15. Try the scan tool on another Catera if one is available. The Catera uses ISO serial data and communicates with the scan tool on DLC pin 7. Most other GM OBD II vehicles use Class 2 serial data on DLC pin 2. Therefore, testing the scan tool on a vehicle that uses a different serial data system will not verify that the tool can communicate properly on pin 7. An alternate approach is to try a different scan tool on the same vehicle if one is available. Before trying a different scan tool, check for a poor connection between the DLC and the scan tool cable. Refer to Overall Vehicle Information / Diagrams / Diagnostic Aids for Checking Terminal Contact procedure.

18. Before trying a different scan tool, check for a poor connection between the DLC and the scan tool cable. Refer to Overall Vehicle Information / Diagrams / Diagnostic Aids for Checking Terminal Contact procedure.