1988 GMC S15 Service and Repair Manual

This factory service and repair manual for the 1988 GMC S15 lists three gasoline engines: a 2.8L overhead-valve V6, a 4.3L overhead-valve V6 of 262 cubic inches and a 2.5L overhead-valve inline-four. Three two-door bodies are covered — extended cab, standard cab and cab and chassis — in Base, Gypsy, High Sierra and Sierra Classic trim. A larger V6 in a compact truck changes what the cooling, fuel and driveline systems are asked to do, and the manual accounts for that with engine-specific procedures, specifications, torque values, wiring diagrams and diagnostics.

Engines covered

• 2.8L V6 (173 cu in) — OHV, naturally aspirated, gasoline
• 4.3L V6 (262 cu in) — OHV, naturally aspirated, gasoline
• 2.5L inline-four (151 cu in) — OHV, naturally aspirated, gasoline

Body styles covered

• 2-door extended cab pickup
• 2-door standard cab pickup
• 2-door cab & chassis

Trims covered

• Base
• Gypsy
• High Sierra
• Sierra Classic

Known issues on the 1988 S15. Two recalls are on the federal record for this year, and both concern replacement lamp assemblies sold for these trucks that lack the amber side reflectors federal lighting rules call for, so the truck is less visible to traffic coming from the side. Two owner complaints are logged, one on the service brakes and one on seat belts. That points toward the lighting and brake sections, where the manual gives circuit wiring diagrams and diagnostics for the lamps, hydraulic procedures and dimensions for the brakes, and torque values for the restraint hardware.