VCM - MIL ON/No DTC's Stored
File in Section: 6E - Engine Fuel & EmissionBulletin No.: 57-65-29A
Date: May, 1996
Subject:
Cold Temperature VCM Reset Causing Loss of DTC's (Update Calibration)
Models:
1995 Chevrolet and GMC S/T Models
with 4.3L Engine (VIN W - RPO L35) without RPO K29
This bulletin is being revised to change with RPO K29 to without RPO K29 in the models section. Please discard Corporate Bulletin Number 57-65-29 (Section 6E - Engine Fuel and Emission)
Condition
Some customers may bring their vehicle in for service the comment that the MIL light (SES) is illuminated.
When the service technician looks for diagnostic trouble codes (using a Tech 1), there are none stored.
This problem only occurs during cold weather vehicle operation, typically in the northern climates.
Cause
During a cold weather start condition, if the battery voltage temporarily drops below 9 Volts, and the ignition switch is rotated rapidly to the crank position, the VCM may reset causing any stored fault DTC's to be erased.
Notice:
Low battery voltage during a start procedure may be a symptom of another problem (discharged battery, wiring or connections, charging system performance, etc.).
Correction
New software has been released to address this condition. Updated calibrations were released to vehicle assembly plants January, 1995.
1. Have the Calibration I.D. checked with a Tech 1.
2. Vehicles identified as having the old calibration should be updated with the new Flash calibration.
Calibration Information
The calibrations listed are FLASH calibrations and NOT available from GMSPO. Service FLASH calibrations are available starting with the July 1995 CD ROM.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation Labor Time
J-6355 0.3 hr