PROM - Unstable Idle/Decel Surge/False Code 42
88chevy11Number: 87-281-6E
Section: 6E
Date: APRIL, 1988
Subject: UNSTABLE IDLE, DECEL SURGE
AND FALSE CODE 42
Model and Year:
1987 M, S/T TRUCKS WITH 2.5L (VIN CODE E) ENGINE
TO: ALL CHEVROLET DEALERS
This bulletin is being revised to update the PROM part numbers and add PROM I.D.'s and PROM broadcast code. All copies of Dealer Service Bulletin 87-213 (Section 6E) dated SEPT., 1987 should be discarded.
Some 1987 M vans and S/T trucks with a 2.5L TBI engine may experience one or more of the following conditions:
1. Idle is unstable, rolls, hunts both hot and cold.
2. Vehicle surges on deceleration.
3. False Code 42 - electronic spark timing
4. Detonation (spark knock) on manual transmission (45-55 mph).
If normal service procedures in the Fuel, Driveability and Emission Manual do not correct the condition, a 1988 calibration PROM is now available and can be used to correct these conditions on the 1987 models listed.
NOTICE TO DEALERS:
When using the above 1988 PROMS in the 1987 vehicles described in this bulletin, scan tools with 1987 programs and CAMS terminals with software versions prior to 19.000 will read only the following information correctly:
Model PROM Application
1. PROM I.D.
2. TROUBLE CODES
3. COOLANT
4. TPS
5. RPM
6. MPH
7. BLOCK LEARN
8. INTEGRATOR
9. IDLE AIR CONTROL
10. MAP
Modifications have been made starting in CAMS software version 19.000 that will allow for correct reading of all information. 1988 versions of scan tool programs will include the ability to read all information correctly.
CAMS terminals with software versions 18.025 and earlier should not be used for diagnosis of the listed PROMS in the described vehicles.
For repairs to vehicles under warranty use:
Labor OP: J6364
Labor Time: S/T .8 hrs
M Van .6 hrs