PROM - Check Engine Code 34 After Short Period of Idling
86chevy03Number: 85-204
Section: 6E
Date: JUNE, 1986
Subject: CHECK ENGINE LIGHT (CODE 34) AFTER SHORT PERIOD OF IDLING
Model and Year: 1984-85 "S/T" TRUCKS WITH 2.8L (VIN CODE B)
ENGINES, MANUAL TRANSMISSIONS, AND CALIFORNIA EMISSIONS
TO: ALL CHEVROLET DEALERS
Some 1984-85 S/T Trucks with manual transmissions and California emissions may set a Code 34 check engine light after a short period of idling.
To determine cause of this condition, perform the diagnostic check for Code 34 in Section 6E7 of the Service Manual.
If the diagnostic check indicates a wiring problem, (grounded or open), correct as required. If the Code 34 check engine light condition persists, inspect for faulty connections at the pressure differential sensor and correct as necessary.
If the diagnostic procedure indicates a faulty pressure differential sensor, replace the PROM with one of the following service PROM's. These PROM's allow for a greater amount of engine vacuum prior to setting a Code 34.
MODEL YEAR SERVICE PROM
1984 1227896
1985 1227897
If the Code 34 check engine condition continues after installation of the Service PROM, replace the pressure differential sensor.
Use applicable labor time and operation numbers.