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 appropriate AIR BAG RESTRAINT SYSTEM article in RESTRAINTS |
| 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. |
There are 2 data lines that can be accessed with a scan tool. The 800 circuit is the UART data line. It allows the inflatable restraint Diagnostic Energy Reserve Module (DERM) to communicate with a scan tool. The Powertrain/Vehicle Control Module (PCM/VCM) connects to the Data Link Connector (DLC) on the 1807 circuit (class 2) so the PCM/VCM can communicate with a scan tool. A scan tool can be connected to the DLC, allowing the scan tool to communicate with the 2 data lines. System operations can then be monitored for diagnostic purposes.
COMPONENT LOCATIONS
| Component | Location |
|---|---|
| Brake Pressure Modulator Valve (BPMV - 4.3L) | Driver Side Of Engine Compartment Above Wheel House. (Scheme 2) |
| Data Link Connector (DLC) | Lower Driver Side Of Instrument Panel. (Scheme 5) |
| Driver Information Display Center (DIDC - Bravada Only) | Front Of Overhead Console. (Scheme 4) |
| Electronic Brake Control Module (EBCM - 2.2L Only) | Below BPMV. (Scheme 1) |
| Inflatable Restraint Diagnostic Energy Reserve Module (DERM) | Behind Passenger Side Kick Panel. (Scheme 3) |
| Instrument Panel Fuse Block | Driver Side Of Instrument Panel. (Scheme 6) |
| Powertrain Control Module (PCM - 2.2L) | Passenger Side Of Engine Compartment. (Scheme 7) |
| Remote Control Door Lock Receiver (RCDLR) | Behind Lower Driver Side Of Instrument Panel, Near Parking Brake. (Scheme 8) |
| Transfer Case Shift Control Module (TCSCM) | Behind Center Of Instrument Panel. (Scheme 9) |
| Vehicle Control Module (VCM - 4.3L) | Passenger Side Of Engine Compartment. (Scheme 10) |
| C100 (2.2L Engine) | Engine Harness To Front Of Dash Harness, Driver Rear Of Engine Compartment Above Brake Booster. (Scheme 11) |
| C100 (4.3L Engine) | Engine Harness To Front Of Dash Harness, Driver Rear Of Engine Compartment Above Brake Booster. (Scheme 2) |
| C175 (2.2L Engine) | Near PCM On Passenger Side Of Engine Compartment. (Scheme 12) |
| C200 (Pickup) | Behind Passenger Side Of Instrument Panel. (Scheme 13) |
| C200 (Utility) | Behind Passenger Side Of Instrument Panel. (Scheme 14) |
| C201 | Behind Passenger Side Of Instrument Panel. (Scheme 15) |
| C208 (Bravada) | Behind Upper Driver Side Of Instrument Panel. (Scheme 16) |
| C217 | Behind Passenger Side Of Instrument Panel. (Scheme 15)& (Scheme 17) |
| C220 (Utility) | Top Center Of Instrument Panel. (Scheme 18) |
| C240 (Non-Base Pickup) | Top Center Of Instrument Panel. (Scheme 18) |
| G102 (2.2L Engine) | Driver Side Of Engine, Below Exhaust Manifold. (Scheme 19) |
| G102 (4.3L Engine) | Passenger Rear Of Engine, On Cylinder Head. (Scheme 20) |
| G104 (2.2L Engine) | Driver Rear Of Cylinder Head. (Scheme 21) |
| G104 (4.3L Engine) | Driver Rear Of Cylinder Head. (Scheme 20) |
| G107 (4.3L Engine) | Driver Rear Of Engine Compartment, Left Of A/C Compressor Relay. (Scheme 22) |
| P100 | At Cowl On Driver Rear Of Engine Compartment. (Scheme 23) |
| P101 | Rear And Below Blower Motor. (Scheme 17) |
| S110 (2.2L Engine) | Engine Harness, Near Generator Harness Breakout. (Scheme 19) |
| S110 (4.3L Engine) | Engine Harness, Near Dash & Chassis Breakout. (Scheme 20) |
| S214 | Front Of Dash Harness, Near P100. (Scheme 16) |
| S220 | Instrument Panel Harness, Near Relay Center Breakout. (Scheme 24) |
| S233 | Front Of Dash Harness, Near Steering Column Breakout. (Scheme 25) |
| S241 | Front Of Dash Harness, Near DLC. (Scheme 26) |
COMPONENT LOCATIONS
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Scheme 6
Scheme 7
Scheme 8
Scheme 9
Scheme 10
Scheme 11
Scheme 12
Scheme 13
Scheme 14
Scheme 15
Scheme 16
Scheme 17
Scheme 18
Scheme 19
Scheme 20
Scheme 21
Scheme 22
Scheme 23
Scheme 24
Scheme 25
Scheme 26
PCM/VCM CLASS 2 DATA LINE
- Ensure there is proper connection between scan tool and DLC and no loose or missing DLC terminals.
- If PCM/VCM is not accessible with a scan tool, check for an open in circuit 1807 between DLC terminal No. 2 and PCM/VCM. (Scheme 29) See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/communication-devices/#data-link-communications-system).
- 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, perform appropriate test. See «SYSTEM TESTS»(/chevrolet/blazer/s15-1994-1998/remont/communication-devices/#data-link-communications-system).
UART DATA LINE DIAGNOSIS
Refer to flowchart. (Scheme 27)
Scheme 27
CLASS 2 DATA LINE DIAGNOSIS
Refer to flowchart. (Scheme 28)
