Introduction to Diagnosis

Introduction
The systematic troubleshooting information covered offers a practical and systematic approach to diagnosing 4L30-E transmission, using information that can be obtained from road tests, electrical diagnosis, oil pressure checks or noise evaluation.
The key to correcting a complaint is to make use of all of the available symptoms and logically letting them direct you to the cause.
When dealing with automatic transmission complaints, it is best to gather as many symptoms as possible before making the decision to remove the transmission from the vehicle.
Frequently, the correction of the complaint does not require removal of the transmission from the vehicle.