Engine Controls - O2 Sensor Cracked, DTC 44

BULLETIN NUMBER: 93-6F-56A
SECTION: 6F Engine Exhaust
NUMBER: 2
CORPORATE REFERENCE NUMBER: 2666O4R
DATE: May 1993

SUBJECT:
POOR ENGINE PERFORMANCE/ILLUMINATION OF SES LAMP/DTC 44 (NEW CROSSOVER PIPE W/SHIELD)

MODELS:
1993 MIL WITH 4.3L ENG EXCL RPO NB2

THIS BULLETIN CANCELS AND REPLACES GMC TRUCK BULLETIN 93-6F-56, DATED MARCH 1993. IT IS BEING REVISED TO CLARIFY THE ENGINES OF THE MODELS AFFECTED. THEY ARE "Z" AND "W", NOT "E" AND "W". ALL COPIES OF BULLETIN 93-6F-56 SHOULD BE DISCARDED.

CONDITION

The SES light on the instrument panel cluster may illuminate on some 1993 M/L vans as a result of a Diagnostic Trouble Code (DTC) 44 being set. The symptoms of this condition would be poor engine performance, increased black exhaust smoke, a cracked sensor element and possibly the recurrence of a Heated Oxygen Sensor replacement for DTC 44 code.

CAUSE

The 1993 M/L vans have a larger diameter exhaust crossover pipe which allows for greater condensation in the system. Thus there is a chance for water droplets to flow down through the exhaust cross-over and make contact with the Heated Oxygen Sensor. The result is thermal cracks inside the sensor element and the setting of DTC 44.

CORRECTION

To minimize this condition, a new design exhaust crossover pipe has been released for production and service. The new design incorporates a sleeve shield around the Heated Oxygen Sensor which eliminates the possibility of water droplets coming into contact with the sensor and causing thermal cracks inside the sensor element.

SERVICE PROCEDURE

Figure 1 - Locating Oxygen Sensor Shield In Exhaust Crossover:

Using a scan tool determine if the vehicle has set a DTC 44 (reference 1993 Light Duty Truck Fuel and Emissions Service Manual X-9336). Inspect the exhaust crossover pipe by using a probe in the oxygen sensor hole (see Figure 1). Determine if a sleeve shield already exists in the crossover pipe. If there is no sleeve found in the pipe than replacement of the crossover pipe and the heated oxygen sensor is required to eliminate DTC code 44.

VEHICLES INVOLVED

Vehicles built after the following VIN breakpoint were manufactured with a redesigned cross over pipe with a sleeve shield to protect the Heated Oxygen Sensor from possible water contamination and eliminating cracking of the sensor.

Year:1993
VIN: PB502366

SERVICE PARTS INFORMATION




Parts are currently available from GMSPO.

WARRANTY INFORMATION
For vehicles repaired under warranty, use:
Labor Op: L2080
Labor Time: See Applicable Labor Time Guide