MIL ON - O2 DTCs, Engine Miss/Roughness
File In Section: 6E - Engine Fuel & EmissionBulletin No.: 76-65-05
Date: August, 1997
Subject:
Engine Rough, Miss, and Oxygen Sensor DTCs
(Replace 02 Sensor/s and/or Connector/s, Solder Exposed Copper Wire Strands to Body Ground Terminal Connection)
Models:
1996-98 Chevrolet and GMC MIL Vans with 4.3L V6
Engine (VIN W - RPO L35)
Built prior to the Following VIN Breakpoints:
Model VIN Breakpoints
Chevrolet WB101260
GMC WB500432
Condition
Some owners may comment about an engine miss and/or roughness and a SES light.
Cause
Some oxygen sensors have been found to be damaged due to water intrusion. Approximately 20% of the oxygen sensors returned for analysis on these models have exhibited this condition. If any oxygen sensor related DTC is stored, moisture may have entered the engine harness through the ground terminal on the front of dash at the extreme passenger side of the engine compartment and damaged the sensors. Oxygen sensors that have been damaged by water may show either actual water droplets in the connector and/or have corrosion on one or more of the sensor's terminals (4). The engine harness connector at the same location should show similar corrosion. Sensors with no corrosion, but water present in the connector will likely be either temporarily (intermittent) or permanently disabled.
Correction
1. Follow the Strategy Based Diagnostics and published procedures for the specific symptom and DTC.
2. Inspect the oxygen sensor connectors for signs of moisture or "bluish-green" corrosion on the terminals and in the connector cavities.
3. If water intrusion is suspected, but no corrosion is evident, the presence of water in the sensor may be checked using a DVOM. It is very important that the sensor be at room temperature when this test is run. If the sensor is warm or if power has been applied to the sensor's heater within the previous 10 minutes, incorrect results will be obtained. Set the meter to measure resistance in the megohm range and connect it across the sensor's purple and tan contacts. A defective sensor will show a value less than 20 megohms, and the value may change continuously while the DVOM is connected to it. A good sensor will show resistance values much higher than 20 megohms, and/or may indicate "OPEN" when the sensor is at room temperature.
4. If these signs are detected, replace the affected oxygen sensor(s), and attempt to remove any obvious traces of water by thoroughly blowing shop air into the harness connector. If corrosion is present on the harness connectors, following the service procedure described in Section 8A-5 of the service manual, replace the affected connectors and terminals of the harness with the harness connector kits listed below. Keep in mind that the new harness connections should be water tight. DO NOT use or apply any type of solder, sealant or wire dryer spray in the oxygen sensor or harness connector areas.
5. For all vehicles with any Oxygen Sensor and/or Misfire and/or System Rich or Lean DTCs, disconnect the ring terminal from the ground stud located at the extreme passenger side of the vehicle. Solder the exposed copper wires within the ring terminal's crimped connector using rosin core solder. Care should be taken to assure that the wire insulation does not melt or pull away from the crimped connector during the solder operation, thus exposing more copper wire. This repair is made to "seal" off a path of water entry.
Important:
all (4) oxygen sensor heater circuits utilize this ground terminal.
6. Record all DTCs encountered during problem diagnosis on the repair order as stated in Service Bulletin # 67-05-02 dated October, 1996. Documentation of Diagnostic Trouble Codes is required in accordance with section 4.2.9 of the GM Claims Processing Manual.
7. Verify the symptom and/or DTC is corrected before returning the vehicle to the owner.
Parts Information
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use the table.
Important:
Labor operation is coded to base vehicle coverage in the warranty system.