Self-Diagnostics System Check Chart B: Data Circuit Problem: Description

You have been directed to this chart as a result of a total loss of communication on CKT 800. This could be due to a wiring or element problem.

NOTE: Numbers in list refer to circled numbers in diagnostic flow chart, see Fig 1. For circuit identification see Figure.

This step checks for an open 800 CKT.
The last step established that CKT 800 is not open. This step will check CKT 800 while it is operating. Normal operating voltage on CKT 800 is between. 1 and 5 volts, fluctuating continuously.
If the dataline is functioning properly, a loss of ground to the IPC may be the cause of a blank IPC.

Fig 1: Diagnostic System Check Chart B: Data Circuit Problem Flow Chart

Courtesy of GENERAL MOTORS CORP.