Diagnostic System Check - VCM-A

4L60-E AUTOMATIC TRANSMISSION

On-Board Diagnostic (OBD) Diagnostic Chart:

On-Board Diagnostic (OBD) System Check:

CIRCUIT DESCRIPTION
The On-Board Diagnostic (OBD) System Check is an organized approach to identifying a problem created by a control module system malfunction. It must be the starting point for any driveability complaint diagnosis. this will direct the service technician to the next logical step in diagnosing the complaint. Understanding the chart and using it properly will reduce diagnostic time and prevent the unnecessary replacement of good parts.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step will isolate if the customer complaint is a Service Engine Soon (MIL) or driveability problem with no MIL.
2. When the ignition switch is turned "ON," the Tech 1 should display serial data. This will determine that the Vehicle Control Module-A (VCM-A) is powered up.
3. Refer to Diagnostic Trouble Code Identification for a list of valid DTCs. An invalid DTC may be the result of a faulty scan tool, VCM-A Programing or VCM-A.
4. This step verifies that the engine will start.
5. Although the control module is powered up, a symptom could exist because of a system fault.
6. Comparison of actual control system data with the Typical Tech 1 Data Values is a quick check to determine if any parameter is not within limits. A base engine problem (i.e., advanced cam timing may substantially alter sensor values).