Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM & COMPONENT TESTSCOMPUTERIZED ENGINE CONTROLSPOWERTRAIN CONTROL MODULE (PCM) CONNECTOR TERMINAL IDENTIFICATIONPOWERTRAIN CONTROL MODULE (PCM) - 4.8L, 5.3L & 6.0L
1999 GMC Forward Control 5.7 R, Automatic
Powertrain Control Module (Pcm) - 4.8L, 5.3L & 6.0L
1999 GMC Forward Control 5.7 R, AutomaticSECTION Powertrain Control Module (Pcm) - 4.8L, 5.3L & 6.0L
POWERTRAIN CONTROL MODULE (PCM) - 4.8L, 5.3L & 6.0L (1)
| Connector | Terminal No. | Wire Color | Function | ||
|---|---|---|---|---|---|
| C1 (Blue) | 1 | BLK | PCM Ground | ||
| C1 (Blue) | 2 | LT GRN | CKP Sensor Voltage Supply | ||
| C1 (Blue) | 3 | PNK/BLK | Fuel Injector No. 3 Control | ||
| C1 (Blue) | 4 | LT GRN/BLK | Fuel Injector No. 2 Control | ||
| C1 (Blue) | 5-10 | ..... | Not Used | ||
| C1 (Blue) | 11 | LT BLU | KS Signal Rear | ||
| C1 (Blue) | 12 | DK BLU/WHT | CKP Sensor Signal | ||
| C1 (Blue) | 13-16 | ..... | Not Used | ||
| C1 (Blue) | 17 | DK BLU | Transmission Range Signal B | ||
| C1 (Blue) | 18 | RED | Transmission Range Signal C | ||
| C1 (Blue) | 19 | PNK | PCM Ignition Supply | ||
| C1 (Blue) | 20 | ORG | PCM Battery Supply | ||
| C1 (Blue) | 21 | YEL/BLK | CKP Sensor Ground | ||
| C1 (Blue) | 22 | ..... | Not Used | ||
| C1 (Blue) | 23 | PPL | Sensor Ground | ||
| C1 (Blue) | 24 | ..... | Not Used | ||
| C1 (Blue) | 25 | TAN | HO2S Bank 2 Sensor 2 Signal Low | ||
| C1 (Blue) | 26 | TAN | HO2S Bank 2 Sensor 1 Signal Low | ||
| C1 (Blue) | 27 | ..... | Not Used | ||
| C1 (Blue) | 28 | TAN/WHT | HO2S Bank 1 Sensor 2 Signal Low | ||
| C1 (Blue) | 29 | TAN/WHT | HO2S Bank 1 Sensor 1 Signal Low | ||
| C1 (Blue) | 30 | LT GRN | Engine Coolant Level Switch | ||
| C1 (Blue) | 31 | ..... | Not Used | ||
| C1 (Blue) | 32 | BLK/WHT | PRND A | ||
| C1 (Blue) | 33 | PPL | TCC Brake Switch | ||
| C1 (Blue) | 34 | WHT | PRND P | ||
| C1 (Blue) | 35 | GRY | Clutch Switch Signal | ||
| C1 (Blue) | 36 | BLK | Fuel Injector No. 1 Control | ||
| C1 (Blue) | 37 | YEL/BLK | Fuel Injector No. 6 Control | ||
| C1 (Blue) | 38 & 39 | ..... | Not Used | ||
| C1 (Blue) | 40 | BLK/WHT | PCM Ground | ||
| C1 (Blue) | 41 | BLK | Sensor Ground | ||
| C1 (Blue) | 42 | ..... | Not Used | ||
| C1 (Blue) | 43 | RED/BLK | Fuel Injector No. 7 Control | ||
| C1 (Blue) | 44 | LT BLU/BLK | Fuel Injector No. 4 Control | ||
| C1 (Blue) | 45 | GRY | Fuel Tank Pressure Sensor Reference Voltage | ||
| C1 (Blue) | 46 | GRY | TP Sensor Reference Voltage | ||
| C1 (Blue) | 47 | GRY | MAP Sensor Reference Voltage | ||
| C1 (Blue) | 48 | GRY | EGR Pintle Position Sensor Reference Voltage | ||
| C1 (Blue) | 49 & 50 | ..... | Not Used | ||
| C1 (Blue) | 51 | DK BLU | KS Signal Front | ||
| C1 (Blue) | 52 | ..... | Not Used | ||
| C1 (Blue) | 53 | BLK | Fuel Tank Pressure Sensor Ground | ||
| C1 (Blue) | 54 | BLK | TP Sensor Ground | ||
| C1 (Blue) | 55 | BRN | EGR Pintle Position Sensor Signal | ||
| C1 (Blue) | 56 | ..... | Not Used | ||
| C1 (Blue) | 57 | ORG | PCM Battery Supply | ||
| C1 (Blue) | 58 | DK GRN | Serial Data | ||
| C1 (Blue) | 59 | YEL | Serial Data | ||
| C1 (Blue) | 60 | ORG/BLK | MAP Sensor Ground | ||
| C1 (Blue) | 61 | PNK/BLK | CMP Sensor Ground | ||
| C1 (Blue) | 62 | ..... | Not Used | ||
| C1 (Blue) | 63 | GRY | ECT Sensor Ground | ||
| C1 (Blue) | 64 | ..... | Not Used | ||
| C1 (Blue) | 65 | PPL | HO2S Bank 2 Sensor 2 Signal High | ||
| C1 (Blue) | 66 | PPL | HO2S Bank 2 Sensor 1 Signal High | ||
| C1 (Blue) | 67 | ..... | Not Used | ||
| C1 (Blue) | 68 | PPL/WHT | HO2S Bank 1 Sensor 2 Signal High | ||
| C1 (Blue) | 69 | PPL/WHT | HO2S Bank 1 Sensor 1 Signal High | ||
| C1 (Blue) | 70 | BRN | Low Oil Level Switch | ||
| C1 (Blue) | 71 | ..... | Not Used | ||
| C1 (Blue) | 72 | YEL | PRND B | ||
| C1 (Blue) | 73 | BRN/WHT | CMP Sensor Signal | ||
| C1 (Blue) | 74 | YEL | ECT Sensor Signal | ||
| C1 (Blue) | 75 | PNK | PCM Ignition Supply | ||
| C1 (Blue) | 76 | BLK/WHT | Fuel Injector No. 5 Control | ||
| C1 (Blue) | 77 | DK BLU/WHT | Fuel Injector No. 8 Control | ||
| C1 (Blue) | 78 | ..... | Not Used | ||
| C1 (Blue) | 79 | WHT | 3-2 Shift Solenoid Control | ||
| C1 (Blue) | 80 | ORG/BLK | Fuel Level Sensor Ground | ||
| C2 (Red) | 1 | BLK/WHT | PCM Ground | ||
| C2 (Red) | 2 | BRN | TCC Control Solenoid | ||
| C2 (Red) | 3-5 | ..... | Not Used | ||
| C2 (Red) | 6 | RED/BLK | Trans Fluid Pressure Control Solenoid High | ||
| C2 (Red) | 7 | RED | EGR Solenoid Supply | ||
| C2 (Red) | 8 | LT BLU/WHT | Trans Fluid Pressure Control Solenoid Low | ||
| C2 (Red) | 9 | DK GRN/WHT | Fuel Pump Relay Control | ||
| C2 (Red) | 10 | WHT | Engine Speed (Tach) Output Signal | ||
| C2 (Red) | 11 | DK BLU | Secondary A/C High Pressure Switch | ||
| C2 (Red) | 12 | ..... | Not Used | ||
| C2 (Red) | 13 | LT BLU/BLK | Cruise Control Engage Signal | ||
| C2 (Red) | 14 | ..... | Not Used | ||
| C2 (Red) | 15 | BRN | Generator L Terminal | ||
| C2 (Red) | 16 | GRY/BLK | 4WD Switch Signal Low | ||
| C2 (Red) | 17 | DK GRN/WHT | A/C Request Signal | ||
| C2 (Red) | 18 | ..... | Not Used | ||
| C2 (Red) | 19 | BLK/WHT | 4WD Front Axle Switch | ||
| C2 (Red) | 20 | LT GRN/BLK | VSS Reference Low | ||
| C2 (Red) | 21 | PPL/WHT | VSS Signal | ||
| C2 (Red) | 22 | RED/BLK | VSS Signal (6.0L) | ||
| C2 (Red) | 23 | DK BLU/WHT | VSS Reference Low (6.0L) | ||
| C2 (Red) | 24 | DK BLU | TP Sensor Signal | ||
| C2 (Red) | 25 | TAN | IAT Sensor Signal | ||
| C2 (Red) | 26 | PPL | Ignition Control No. 1 | ||
| C2 (Red) | 27 | RED | Ignition Control No. 7 | ||
| C2 (Red) | 28 | LT BLU/WHT | Ignition Control No. 6 | ||
| C2 (Red) | 29 | DK GRN/WHT | Ignition Control No. 4 | ||
| C2 (Red) | 30 | ..... | Not Used | ||
| C2 (Red) | 31 | YEL | MAF Sensor Signal | ||
| C2 (Red) | 32 | LT GRN | MAP Sensor Signal | ||
| C2 (Red) | 33 | DK GRN | HVAC Recirculation Door Control | ||
| C2 (Red) | 34 | DK GRN/WHT | EVAP Canister Purge Solenoid Control | ||
| C2 (Red) | 35 | ..... | Not Used | ||
| C2 (Red) | 36 | BRN | AIR Pump Relay Control | ||
| C2 (Red) | 37 & 38 | ..... | Not Used | ||
| C2 (Red) | 39 | RED | CMP Sensor Voltage Supply | ||
| C2 (Red) | 40 | BLK/WHT | PCM Ground | ||
| C2 (Red) | 41 | WHT | EGR Solenoid Ground | ||
| C2 (Red) | 42 | TAN/BLK | TCC Enable Circuit | ||
| C2 (Red) | 43 | DK GRN/WHT | A/C Compressor Clutch Relay Control | ||
| C2 (Red) | 44 | ..... | Not Used | ||
| C2 (Red) | 45 | WHT | EVAP Canister Vent Valve Control | ||
| C2 (Red) | 46 | BRN/WHT | MIL Control | ||
| C2 (Red) | 47 | YEL/BLK | Transmission Shift Solenoid B | ||
| C2 (Red) | 48 | LT GRN | Transmission Shift Solenoid A | ||
| C2 (Red) | 49 | YEL/BLK | Vehicle Speed Output Circuit 128K | ||
| C2 (Red) | 50 | DK GRN/WHT | Vehicle Speed Output Circuit 4K | ||
| C2 (Red) | 51 | YEL/BLK | Transmission Temperature Sensor Signal | ||
| C2 (Red) | 52 & 53 | ..... | Not Used | ||
| C2 (Red) | 54 | PPL | Fuel Level Sensor Signal | ||
| C2 (Red) | 55 | DK GRN | A/C Compressor Cycling Switch Signal | ||
| C2 (Red) | 56 | ..... | Not Used | ||
| C2 (Red) | 57 | BLK | IAT Sensor Ground | ||
| C2 (Red) | 58 & 59 | ..... | Not Used | ||
| C2 (Red) | 60 | BRN | IC Reference Low Bank 1 | ||
| C2 (Red) | 61 | BRN/WHT | IC Reference Low Bank 2 | ||
| C2 (Red) | 62 | GRY | PRND C | ||
| C2 (Red) | 63 | PNK | Transmission Range Signal A | ||
| C2 (Red) | 64 | DK GRN | Fuel Tank Pressure Sensor Signal | ||
| C2 (Red) | 65 | ..... | Not Used | ||
| C2 (Red) | 66 | PPL/WHT | Ignition Control No. 8 | ||
| C2 (Red) | 67 | RED/WHT | Ignition Control No. 2 | ||
| C2 (Red) | 68 | DK GRN | Ignition Control No. 5 | ||
| C2 (Red) | 69 | LT BLU | Ignition Control No. 3 | ||
| C2 (Red) | 70-75 | ..... | Not Used | ||
| C2 (Red) | 76 | LT GRN/WHT | IAC Coil B High | ||
| C2 (Red) | 77 | LT GRN/BLK | IAC Coil B Low | ||
| C2 (Red) | 78 | LT BLU/BLK | IAC Coil A Low | ||
| C2 (Red) | 79 | LT BLU/WHT | IAC Coil A High | ||
| C2 (Red) | 80 | ..... | Not Used | ||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.