LEMON Manuals
: Even more car manuals for everyone: 1960-2025
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GMC
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1989
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Forward Control 4.8 T, Automatic, 400/M40
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Repair and Diagnosis (Single Page)
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Engine Performance
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System
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Air Injection System
July 1:
So it begins
. Don't worry, this is not in the correct legal jurisdiction!
Air Injection System
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Description
Operation
Air Pump
Diverter Valve
California Models (Over 10,000 GVW)
High-Flow Electric Air Control (HFEAC) Valve
Federal (Over 10,000 GVW)
Electric Air Control (EAC) & Electric Air Control With Relief Tube (ECT) Valves
Deceleration Control Valve
Component Testing
Air Pump
Check Valve
Diverter Valve
Air Control Valve
Throttle Body Injection Type
CARBURETED Type
"SERVICE ENGINE SOON" Illuminated (4.8L)
No "SERVICE ENGINE SOON" Light (5.7L)
"SERVICE ENGINE SOON" Light Illuminated (5.7L)
"Service Eng Soon" Test
7.4L "Service Engine Soon" Light Illuminated Flow Chart
Wiring Diagrams