Number: Reissue 86-162
Date: MAY, 1987
Subject: ENGINE CALIBRATION CHANGE TO IMPROVE DRIVEABILITY
AND ELIMINATE FALSE "SERVICE ENGINE SOON" LIGHTS
Model and Year: 1986 CORVETTE
TO: ALL CHEVROLET DEALERS
Chevrolet Dealer Service Bulletin 86-162 is being reissued to provide a revised calibrator
for use on the 1986 corvette with aluminum heads and manual transmission. All copies of
Dealer Service Bulletin 86-162 (Section 6E) dated Oct., 1986 should be destroyed.
New service calibrators (Ref: called Mem-Cal in Shop Manual) have been released for the
1986 Corvette with the 5.7L TPI engine. These calibrators will address the following
- "Rough Idle" on both hot and cold engine. The idle speed is raised to 625 plus
or minus 25 RPM with automatic transmission and 750 plus or minus 50 with manual
- "Chuggle or Shudder" at low speeds - Torque converter clutch (TCC) engagement
speed is raised to 41 MPH with transmission vehicles.
- "Surge" at road load - This improvement is for automatic transmission vehicles
- "Engine Overspeed" in 1st gear - This improvement is for manual transmission
- "Hesitation" on light acceleration with a hot engine.
- "Service Engine Soon" lights - eliminates the following false codes:
A. Code 33 - Mass Airflow Sensor Voltage Low
B. Code 34 - Mass Airflow Sensor Voltage High
C. Code 43 - Electronic Spark Control (ESC) this correction is for cast iron head
Corvettes only (VIN #119016 or earlier).
If normal engine diagnostics and repair do not correct the above conditions, it will be
necessary to replace the calibrator in the ECM. Below is a listing of the new calibrators
and their usages.
I. On Iron-head Corvettes (VIN #119016 or earlier)
A. Manual Transmission use 1227943
B. Automatic Transmission with 2.59 (GM1) Axle use 1227942 with 3.07
(G44) Axle use 1227944
II. On Aluminum Head Corvettes (VIN #119016 or later) and all convertible models
A. Manual Transmission use 1228473
B. Automatic Transmission with 2.59 (GM1) Axle use 1228107 with 2.73
(GU2)/3.07 (G44) use 1228109
Use applicable Labor Time and Operation Numbers.