For the 2008 model year, GM will have one common service schematic format worldwide, fully implemented first in North America (fig. 1). Actually, it was previewed in the 2007 Silverado/Sierra and 2007 Acadia/OUTLOOK service information.
The new format, significantly based on today's familiar schematics, is built to work in conjunction with the new diagnostic format. Here are highlights of what's different:
- Schematic Symbols
- Harness Item Naming
- Splice Depiction
- Option Depiction
- Circuit Function Symbols
- Relay Pin Information
- Subsystem Circuit Details
- What's Not on a Schematic?
- Future Enhancements
SCHEMATIC SYMBOLS
Some schematic component symbols have changed. The majority are very similar to what you've seen previously. Here's an example of one slight difference, a normally closed switch(fig. 2).
Switch actuator schematic symbols are new. Switch actuators depict switch operation: push, pull, rotate, or slide. There are also symbols for switches affected by pressure, temperature, or volume. These symbols are shown connecting to the switch arcs.
Switch Actuator Examples
Symbol | Switch Actuator |
| Push |
| Pull |
| Rotate |
| Slide |
| Pressure |
| Temperature |
| Volume |
HARNESS ITEM NAMING
Here's the difference in the way harness items are named
OLD | NEW |
Component Connectors | |
C1, C2, C3 | X1, X2, X3 |
C100, C200, C300 | X100, X200, X300 |
Splices | |
S100, S200, S300 | J100, J200, J300 |
Splice Packs | |
SP100, SP200, SP300 | JX100, JX200, JX300 |
Grounds | |
G100, G200, G300 | G100, G200, G300 |
TIP: The way items are numbered remains the same, although the prefixes have changed.
SPLICE DEPICTION
Splices are shown physically, so the number of wires coming out of a splice matches that of the harness. Now, splices are shown in a horizontal box (fig. 3). The wires are straighter, so the schematic is easier to read.
OPTION DEPICTION
Brackets are no longer used to separate options. An option decision diamond (fig. 4) is the point at which the circuit branches out to identify the differences between the optional information. And, the option codes are placed directly over the wires they pertain to.
Options that are packaged together are identified with the following:
Definition | OLD | NEW |
With | w/ | + |
Without | w/o | - |
or | / | / |
TIP: A single option does not use the plus sign; it just gets the option code.
CIRCUIT FUNCTION SYMBOLS
Circuit function symbols are not new, but usage is more frequent. There are five core circuit types within diagnostics. The circuit function symbols align with those circuit types:
Diagnostic Circuit Type | Circuit Type Definition | Schematic Symbol |
Voltage | Battery | B+ |
Ignition | IGN | |
AC | xV AC | |
Reference Voltage | xV | |
Serial Data | Class 2 | |
GM LAN | ||
UART | ||
Signal | Signal | |
| ||
Control | Control |
|
| ||
| ||
Ground | Low Reference |
|
Ground |
|
RELAY PIN INFORMATION
Relay pin information (fig. 5) is included on schematics as well as on the top views of fuse blocks within the electrical center identification views. Relays within fuse blocks have the pins 30, 85, 86, 87, 87A shown next to the relay. This properly identifies where to test within the fuse block when included in diagnostics.
TIP: For relays taped to a harness or clipped to a bracket, the connector pin numbers are shown instead of the relay pin numbers.
SUBSYSTEM CIRCUIT DETAILS
Previously the level of detail shown within a subsystem schematic varied, specifically in the Ground and Serial Data areas. Three main areas are different when shown within a subsystem schematic -- power supply circuits, ground circuits, and serial data circuits.
TIP: The power distribution schematics, ground distribution schematics, and data communication schematics show all of the circuit details that they did previously.
Power supply circuits (fig. 6) within a subsystem schematic show all aspects of the circuit that may affect the subsystem's functionality, but are shown differently. To see all of the circuit detail, click on the fuse symbol to go to the Power Distribution schematic where the circuit is shown in detail.
Ground circuits (fig. 7) within a subsystem schematic show a wire coming out of the component as a solid wire transitioning to a dashed wire, connecting to a ground symbol. The dashed wire represents additional harness item detail, such as splices and inline harness connections between the component and the ground point. Components that are on the same schematic page that go to the same ground point are connected using the option diamond symbol. To see all of the circuit detail, click on the ground symbol to go to the Ground Distribution schematic where the circuit is shown in detail.
Serial data circuits (fig. 8) within a subsystem schematic are shown functionally. They are included to depict the relationship between the components that receive signals and other components that take some action based upon those signals. In the past, circuit detail was shown to represent this relationship. Generally, a circuit malfunction within a serial data circuit affects the functionality of more than one subsystem, and the diagnostics would likely lead to the Data Communications section for diagnosis of a U-type DTC.
The serial data circuits are depicted as a dashed wire from each of the components that are "talking" to each other. The dashed wires join at a serial data symbol. To see all of the circuit detail, click on the serial data symbol to go to the Data Communication Schematics where the circuit is shown in detail.
WHAT'S NOT ON A SCHEMATIC?
The following are no longer on schematics:
Connector Terminal Symbols -- The terminal symbol at a component where the connector attaches directly to the component is not shown as a half circle. These symbols are shown only if the component has a pigtail connection and is shown for inline harness connections.
CONN ID Boxes -- These were the little boxes indicating, for instance, that C1 was a 24 BK connector and C2 was a 24 GY connector. This information is shown in the connector end view pinout tables.
Wire Diameter Sizes -- The wire sizes have been moved to the connector end view pinout tables. The wire size precedes the wire color.
Circuit Functional Names -- This text went next to the circuit function symbol. In some instances, another icon is used as necessary to depict the function. For example, an arrow pointing to the left is used to describe left. The full text circuit functional name appears in the connector end view pinout tables as previously.
Important Icons -- These were triangular icons with an exclamation point in them, typically shown next to twisted wires, linked to a table that listed the wire twist specification. The wire twist specification (typically 9, 10, or 12) are now shown directly on the schematic above the wire twist symbol.
FUTURE ENHANCEMENTS
Schematic Electronic Navigation -- significantly improves navigating from a schematic to supporting information.
Common Schematic Layout -- provides more of a consistent look for the same subsystem between vehicles.
Look for these changes in SI on the 2008 model year schematics.
- Thanks to Lou Winters
