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) - 7.4L ("C" & "K" SERIES)
1999 GMC Forward Control 5.7 R, Automatic
Powertrain Control Module (Pcm) - 7.4L ("C" & "K" Series)
1999 GMC Forward Control 5.7 R, AutomaticSECTION Powertrain Control Module (Pcm) - 7.4L ("C" & "K" Series)
POWERTRAIN CONTROL MODULE (PCM) - 7.4L ("C" & "K" SERIES) (1)
| Connector | Terminal No. | Wire Color | Function | ||
|---|---|---|---|---|---|
| C1 (Blue) | 1 & 2 | ..... | Not Used | ||
| C1 (Blue) | 3 | BRN/WHT | CMP Sensor 1x Signal | ||
| C1 (Blue) | 4-6 | ..... | Not Used | ||
| C1 (Blue) | 7 | TAN | HO2S Bank 2 Sensor 1 Low | ||
| C1 (Blue) | 8 | PNK/BLK | CMP Low | ||
| C1 (Blue) | 9 | PPL | Fuel Gauge | ||
| C1 (Blue) | 10-13 | ..... | Not Used | ||
| C1 (Blue) | 14 | BRN | AIR Relay Control (Calif. Only) | ||
| C1 (Blue) | 15 | YEL/BLK | VSS Signal | ||
| C1 (Blue) | 16 & 17 | ..... | Not Used | ||
| C1 (Blue) | 18 | PPL/WHT | Dual Tank Fuel Module | ||
| C1 (Blue) | 19 | PPL/WHT | HO2S Bank 1 Sensor 1 High | ||
| C1 (Blue) | 20 | PPL | HO2S Bank 1 Sensor 2 High | ||
| C1 (Blue) | 21 | PPL | HO2S Bank 2 Sensor 1 High | ||
| C1 (Blue) | 22 | PPL/WHT | HO2S Bank 2 Sensor 2 High | ||
| C1 (Blue) | 23 | ..... | Not Used | ||
| C1 (Blue) | 24 | TAN | HO2S Bank 1 Sensor 2 Low | ||
| C1 (Blue) | 25 | TAN/WHT | HO2S Bank 1 Sensor 1 Low | ||
| C1 (Blue) | 26 | TAN/WHT | HO2S Bank 2 Sensor 2 Low | ||
| C1 (Blue) | 27 | ..... | Not Used | ||
| C1 (Blue) | 28 | PPL | CKP Low | ||
| C1 (Blue) | 29 | LT GRN/BLK | VSS Low | ||
| C1 (Blue) | 30 | PPL/WHT | VSS Signal | ||
| C1 (Blue) | 31 | YEL | CKP Sensor 4x Signal | ||
| C1 (Blue) | 32 | ..... | Not Used | ||
| C2 (Red) | 1 | ..... | Not Used | ||
| C2 (Red) | 2 | WHT | EVAP Canister Vent Solenoid Control | ||
| C2 (Red) | 3 | ..... | Not Used | ||
| C2 (Red) | 4 | YEL/BLK | 2-3 Shift Solenoid Control | ||
| C2 (Red) | 5 | ..... | Not Used | ||
| C2 (Red) | 6 | LT GRN | 1-2 Shift Solenoid Control | ||
| C2 (Red) | 7 | BRN | TCC PWM Solenoid Control | ||
| C2 (Red) | 8 | BLK | Fuel Injector No. 1 Control | ||
| C2 (Red) | 9 | DK BLU/WHT | Fuel Injector No. 8 Control | ||
| C2 (Red) | 10 | BRN | EGR Pintle Position Signal | ||
| C2 (Red) | 11 | LT GRN/BLK | Fuel Injector No. 2 Control | ||
| C2 (Red) | 12 | RED/BLK | Fuel Injector No. 7 Control | ||
| C2 (Red) | 13 | LT GRN/WHT | IAC Coil B High | ||
| C2 (Red) | 14 | LT BLU/WHT | IAC Coil A High | ||
| C2 (Red) | 15 | BLK/WHT | Fuel Injector No. 5 Control | ||
| C2 (Red) | 16 | YEL/BLK | Fuel Injector No. 6 Control | ||
| C2 (Red) | 17 & 18 | ..... | Not Used | ||
| C2 (Red) | 19 | DK BLU | KS Signal | ||
| C2 (Red) | 20 | ..... | Not Used | ||
| C2 (Red) | 21 | LT GRN | MAP Sensor Signal | ||
| C2 (Red) | 22 | TAN | IAT Sensor Signal | ||
| C2 (Red) | 23 | YEL | ECT Sensor Signal | ||
| C2 (Red) | 24 | DK BLU | TP Sensor Signal | ||
| C2 (Red) | 25 | DK GRN | Fuel Tank Vacuum Sensor Signal | ||
| C2 (Red) | 26 | ..... | Not Used | ||
| C2 (Red) | 27 | YEL/BLK | TFT Sensor Signal | ||
| C2 (Red) | 28 | YEL | MAF Sensor Signal | ||
| C2 (Red) | 29 | LT GRN/BLK | IAC High | ||
| C2 (Red) | 30 | LT BLU/BLK | IAC Low | ||
| C2 (Red) | 31 | LT BLU/BLK | Fuel Injector No. 4 Control | ||
| C2 (Red) | 32 | PNK/BLK | Fuel Injector No. 3 Control | ||
| C3 (Clear) | 1 | DK GRN/WHT | A/C Compressor Clutch Relay Control | ||
| C3 (Clear) | 2 | DK GRN/WHT | EVAP Canister Purge Solenoid Control | ||
| C3 (Clear) | 3 | ..... | Not Used | ||
| C3 (Clear) | 4 | BLK | ECT/TP Sensor Ground | ||
| C3 (Clear) | 5 | ..... | Not Used | ||
| C3 (Clear) | 6 | RED/BLK | Pressure Control Solenoid High | ||
| C3 (Clear) | 7 | DK BLU/WHT | Input Shaft Speed Sensor Low | ||
| C3 (Clear) | 8 | RED/BLK | Input Shaft Speed Sensor High | ||
| C3 (Clear) | 9 | WHT | IC Control | ||
| C3 (Clear) | 10 | ..... | Not Used | ||
| C3 (Clear) | 11 | RED | Transmission Range C Input | ||
| C3 (Clear) | 12 | GRY | TP Sensor Reference Voltage | ||
| C3 (Clear) | 13 | PPL/WHT | Fuel Level Signal | ||
| C3 (Clear) | 14 | DK BLU | A/C Recirculation | ||
| C3 (Clear) | 15 | ..... | Not Used | ||
| C3 (Clear) | 16 | LT BLU/WHT | Pressure Control Solenoid Low | ||
| C3 (Clear) | 17 | BLK/WHT | PCM Ground | ||
| C3 (Clear) | 18 | BLK/WHT | PCM Ground | ||
| C3 (Clear) | 19 | BLK | Sensor Ground (IAT/MAP/EGR) | ||
| C3 (Clear) | 20 | ..... | Not Used | ||
| C3 (Clear) | 21 | ORG | Battery Voltage | ||
| C3 (Clear) | 22 | DK BLU | Transmission Range B Input | ||
| C3 (Clear) | 23 | PNK | Transmission Range A Input | ||
| C3 (Clear) | 24 | ..... | Not Used | ||
| C3 (Clear) | 25 | DK GRN/WHT | A/C Request Signal | ||
| C3 (Clear) | 26 | ..... | Not Used | ||
| C3 (Clear) | 27 | GRY | Reference Voltage (EGR/MAP) | ||
| C3 (Clear) | 28 & 29 | ..... | Not Used | ||
| C3 (Clear) | 30 | DK GRN | A/C Compressor Cycling Switch Signal | ||
| C3 (Clear) | 31 & 32 | ..... | Not Used | ||
| C4 (Black) | 1 | DK GRN/WHT | Fuel Pump Relay Control | ||
| C4 (Black) | 2 | ..... | Not Used | ||
| C4 (Black) | 3 | DK GRN/WHT | VSS Output Signal (TCC/Radio/Cruise Control) | ||
| C4 (Black) | 4 | DK GRN | VSS Output Signal (Speedometer) | ||
| C4 (Black) | 5 | BRN/WHT | MIL Control | ||
| C4 (Black) | 6-9 | ..... | Not Used | ||
| C4 (Black) | 10 | PPL | Brake Signal | ||
| C4 (Black) | 11 | PPL | Serial Data (Class II) | ||
| C4 (Black) | 12 | BLK | Dual Fuel Module Return | ||
| C4 (Black) | 13 | BRN | Ignition Voltage | ||
| C4 (Black) | 14 & 15 | ..... | Not Used | ||
| C4 (Black) | 16 | RED | EGR Valve Feed | ||
| C4 (Black) | 17 | ..... | Not Used | ||
| C4 (Black) | 18 | PNK | Ignition Voltage | ||
| C4 (Black) | 19 | ..... | Not Used | ||
| C4 (Black) | 20 | WHT | EGR Valve Control | ||
| C4 (Black) | 21 & 23 | ..... | Not Used | ||
| C4 (Black) | 24 | LT BLU/BLK | Cruise Engaged Signal | ||
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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.