For 1990-2009 cars

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

2. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communications
2 |

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the body control module.

Does the scan tool communicate with the body control module?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Data Line in Data Link Communications

3 |

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the memory seat module.

Does the scan tool communicate with the memory seat module?

Go to Step 4

Go to Scan Tool Does Not Communicate with Keyword 82 Data Line in Data Link Communications

4 | Select the body control module display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 5 | Go to Symptoms
5 | Does the scan tool display any DTCs which begin with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Data Line in Data Link Communications | Go to Step 6
6 | Does the scan tool display DTC B1552, B1556 or B1558 in the body control module? | Go to Diagnostic Trouble Code (DTC) List/Type in Body Control System | Go to Step 7
7 | Does the scan tool display DTC B1973, B1982 or B1983 in the body control module? | Go to Diagnostic Trouble Code (DTC) List/Type in Body Control System | Go to Step 8
8 | Does the scan tool display DTCs beginning with a P code in the engine control module? | Go to Diagnostic Trouble Code (DTC) List/Type in Engine Control Systems | Go to Step 9
9 | Does the scan tool display one of the following DTCs in the memory seat module?

• | DTC 18

• | DTC 20

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Symptoms