On-Board Diagnostic (OBD) System Check - Revised
File In Section: 6E - Engine Fuel & EmissionBulletin No.: 51-65-33
Date: June, 1995
Subject:
Section 3 - Driveability and Emissions Control Module Systems - Revised On-Board Diagnostic (OBD) System Check
Models:
1993 Chevrolet and GMC Truck C/K, G Models
with 6.2L Diesel Engine (VIN C - RPO LH6)
The ON-BOARD DIAGNOSTIC SYSTEM CHECK for 1993 vehicles with a PCM does not function like a "typical" OBD system check. The proper operation of the system is as follows:
^ Ignition "ON," engine "OFF" - MIL WILL ONLY come "ON" for 2 seconds during bulb check. (PCM must power down to get another MIL bulb check).
^ Ignition "ON," engine "OFF" - The MIL WILL NOT flash DTC 12 when diagnostic terminal Is grounded (A and B terminals at DLC), but will flash diagnostic trouble codes if present.
^ The TECH I WILL NOT flash the MIL when commanded during the OBD System Check.
CORRECTION
^ A new diagnostic chart for the ON-BOARD DIAGNOSTIC SYSTEM CHECK has been created to properly perform OBD System Check.
^ CHART A-2, FACING PAGE AND DIAGNOSTIC CHART MUST BE DISREGARDED.
This information replaces the information found in Section 3, under ON-BOARD DIAGNOSTIC SYSTEM CHECK and CHART A-2.