Section 3 · Pages 45–254 (210 pages)

Computer Command Control (Scan Tool Diagnosis)

From the 1991 GMC Light Duty Truck Fuel, Emissions and Driveability Manual

The largest section: the Computer Command Control system and its diagnosis with a Scan tool. It describes the ECM/PCM inputs (MAP, oxygen, throttle position, vehicle speed and intake air temperature sensors, park/neutral and power steering pressure switches, distributor reference and A/C signals), then gives the A-series diagnostic charts, trouble code charts, connector repair, ECM/PCM terminal voltages and MEM-CAL replacement, and ECM and PCM wiring diagrams for each engine, including those with the 4L80-E transmission.

Read this section free, starting at page 45

What this section covers

  • ECM/PCM inputs and sensors
  • Code identification
  • Chart A diagnostics (no Service Engine Soon light, no ALDL data, crank but won't run)
  • Trouble code charts
  • Metri-Pack, Weather-Pack and Compact Three connectors
  • ECM/PCM terminal voltages and replacement
  • ECM and PCM wiring diagrams by engine
Year
1991
Make
GMC
Vehicle
C/K Trucks, G Vans, Light Duty Trucks, M Vans (Astro/Safari), P Forward Control, R/V Trucks, S/T Trucks, Trucks
Type
Fuel & Emissions, Supplement
Models
C/K, R/V, P, G, S/T, M 10–30
Publication
X-9136
Pages
406

What’s inside

Fuel and emissions manual

  1. 1General Informationpp. 7–24
  2. 2Driveability Symptomspp. 25–44
  3. 3Computer Command Control (Scan Tool Diagnosis)pp. 45–254
  4. 4Fuel Control System (TBI 220 and 700)pp. 255–300
  5. 5Evaporative Emission Control System (EECS)pp. 301–308
  6. 6Ignition System and ESTpp. 309–318
  7. 7Electronic Spark Control (ESC)pp. 319–326
  8. 8Air Management Systempp. 327–336
  9. 9Exhaust Gas Recirculation (EGR) Systempp. 337–352
  10. 10Automatic and Manual Transmission Controlspp. 353–360
  11. 11Positive Crankcase Ventilation (PCV)pp. 361–366
  12. 12Thermostatic Air Cleaner (THERMAC)pp. 367–372
  13. 13Special Toolspp. 373–380
  14. 14Abbreviations and Glossary of Termspp. 381–384
  15. IndexAlphabetical index of subjects with section and page references.pp. 385–406

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