DESCRIPTION & OPERATION
| WARNING | Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in AIR BAG RESTRAINT SYSTEM article. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. |
The 800 circuit allows the Diagnostic Energy Reserve Module (DERM) and PCM to communicate with each other and a scan tool. A scan tool can be connected to the DLC, allowing the scan tool to communicate with the components on the data line. System operations can then be monitored for diagnostic purposes.
COMPONENT LOCATIONS
| Component | Location (Fig. No.) |
|---|---|
| Brake Pressure Modulator Valve (BPMV) | Driver Side Of Engine Compartment At Wheel House (Scheme 1) |
| Data Link Connector (DLC) | Under Driver Side Of Instrument Panel (Scheme 2) |
| Inflatable Restraint Diagnostic Energy Reserve Module (DERM) | Behind Center Of Instrument Panel |
| Powertrain Control Module (PCM - Gasoline) | Under Passenger Side Of Instrument Panel (Scheme 3) |
| Powertrain Control Module (PCM - Diesel) | Under Passenger Side Of Instrument Panel (Scheme 4) |
| Radio Receiver | Behind Center Of Instrument Panel (Scheme 5) |
| Remote Keyless Entry Module (RKEM) | Behind Center Of Instrument Panel |
| C100 | Driver Rear Of Engine Compartment At Bulkhead (Scheme 1) |
| C200 | Behind Passenger Side Of Instrument Panel, In Foam Wrap (Scheme 3) |
| C298 | Behind Driver Side Of Instrument Panel, Near Convenience Center (Scheme 6) |
| P101 | Passenger Rear Of Engine Compartment At Bulkhead |
| G103 (VIN H & K) | Driver Front Of Engine, Near Thermostat Housing (Scheme 7) |
| G103 (VIN N) | Driver Front Of Engine, Near Thermostat Housing (Scheme 8) |
| S103 | Engine Harness, Near Ignition Coil Breakout |
| S103 (VIN F) | Engine Harness, Near A/C High Pressure Switch |
| S103 (VIN P) | Engine Harness, Near Underhood Lamp Breakout |
| S103 (VIN Z, H, K & N) | Engine Harness, Near Generator Cable Breakout |
| S215 | Instrument Panel Harness, Near Instrument Panel Breakout |
| S227 | Instrument Panel Harness, Near Turn Signal Flasher Breakout |
COMPONENT LOCATIONS
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Scheme 6
Scheme 7
Scheme 8
SERIAL DATA LINE
- Ensure there is proper connection between scan tool and DLC and no loose or missing DLC terminals.
- If all components are not accessible with a scan tool, check for an open in circuit 800 between DLC terminal "M" and S227. (Scheme 10)and (Scheme 11).
- If one component is not accessible with a scan tool, check for an open in circuit 800 between component and S227. (Scheme 11)
- Visually inspect for obvious signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harnesses and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. These circuits may be intermittent or resistive when loaded and should be checked by monitoring the voltage drop with the system under load.
- Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary. If no fault is found, go to «SYSTEM TESTS»(/gmc/suburban/i-1992-1999/remont/communication-devices/#data-link-communications-system).
SERIAL DATA LINE DIAGNOSIS
For serial data line diagnosis, refer to flowchart. (Scheme 9)
