S15/T15 4WD P/U V6-173 2.8L (1985)
PROM - Programmable Read Only Memory: All Technical Service Bulletins
MIL ON, DTC 34 (Differential Pressure Senor) Set
NUMBER:
86-B-95
GROUP:
6D - Engine Electrical
DATE:
June, 1986
SUBJECT:
CHECK ENGINE LIGHT (CODE 34) AFTER A SHORT PERIOD OF IDLING
MODELS:
1984-85 S/T TRUCKS WITH 2.8L (VIN CODE B) ENGINES, MANUAL TRANSMISSIONS, AND CALIFORNIA EMISSIONS
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 idlng. 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 condition persists, inspect for faulty connections at the differential pressure
sensor and correct as necessary.
If the diagnostic procedure indicates a faulty differential pressure sensor, replace the prom with one of the following service proms. These proms 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 condition continues after installation of the service prom, replace the differential pressure sensor. Use applicable Labor Time and
Operation Number.
