Case Study2004 Chevrolet Tahoe -No Generic

Communication

2004 Chevrolet TahoeThis vehicle was located at Sullivan Pontiac Buick.

The concern was that the vehicle would communicate with the TECH 2 scantool, but would not communicate with APPLUS equipment.

2004 Chevrolet Tahoe

2004 Chevrolet Tahoe

2004 Chevrolet Tahoe

2004 Chevrolet TahoeThe first step is to review communication schematics for the vehicle you are working on.

This is a Class 2 communication protocol.

SP205 Schematic Part I

SP205 Schematic Part II

Splice Pack 205

Spice Pack 205-Connector Endview

2004 Chevrolet TahoeThe second step is to scope the Class 2 line.

A BOB was attached to the vehicle at the DLC.

The scope probes were placed in Pin # 2 on the BOB.

Class 2 level was below threshold.

Class 2 Level below Threshold

The class 2 level was too low.

2004 Chevrolet TahoeThe third step was to take the comb out of the splice pack and jumper each module line.

Every terminal on the SP205 was at threshold except pin# H

Class 2 Level at Threshold

This was the voltage level at all pins except pin# H.

SP205 Schematic Part II

Class 2 Level below Threshold

This was the voltage level denoted at pin# H.

Summary Terminal H was backed out of the SP205 connector and communication was restored on this vehicle at a generic level.

A loading effect is taking place on this circuit per a wiring or module related issue.