BUZZERS, RELAYS & TIMERS
| Component | Location | |
|---|---|---|
| A/C Clutch Relay | On top of plenum, behind right side of dash. | |
| A/C-Heater Blower Relays | On top of plenum, behind right side of dash. | |
| Auxiliary Cooling Fan Relay | On left front inner fender panel, near firewall. | |
| Downshift Relay (THM 400/3L80) | ||
| 5.7L | On right side of firewall, behind battery junction block cover. (Scheme 1) | |
| 7.4L - 1989 | On right side of firewall, behind battery junction block cover. (Scheme 2) | |
| 7.4L - 1990 | On right side of firewall, behind battery junction block cover. (Scheme 3) | |
| Right Side Of Firewall View | On right side of firewall, behind battery junction block cover. (Scheme 4) | |
| Auxiliary Battery Relay | On left front inner fender panel, above wheelwell. | |
| Cold Advance Control Relay (6.2L) | On right side of firewall, behind battery junction block cover. (Scheme 4) | |
| Foglight Relay | Behind dash, above convenience center, next to hazard flasher. (Scheme 5) | |
| Fuel Pump Relay | ||
| 4.3L Engine | On right side of firewall, behind battery junction block cover. (Scheme 6) | |
| 5.7L | On right side of firewall, behind battery junction block cover. (Scheme 1) | |
| 7.4L - 1989 | On right side of firewall, behind battery junction block cover. (Scheme 2) | |
| 7.4L - 1990 | On right side of firewall, behind battery junction block cover. (Scheme 3) | |
| Right Side Of Firewall View | On right side of firewall, behind battery junction block cover. (Scheme 4) | |
| Glow Plug Controller Relay | On top of engine, above right valve cover. | |
| Hazard Flasher Relay | Under left side of dash, near convenience center. | |
| Headlight Relay | Behind left side of dash, above convenience center. (Scheme 5) | |
| Horn Relay | On convenience center, below left side of dash. (Scheme 5) | |
| Transfer Case Relay | On right side of firewall, behind battery junction block cover. (Scheme 4) | |
| Turn Signal Flasher Relay | On convenience center. | |
BUZZERS, RELAYS & TIMERS LOCATION
CIRCUIT PROTECTION DEVICES
| Component | Location | |
|---|---|---|
| Circuit Breakers | ||
| Accessory/Battery | On fuse block. | |
| Accessory/Ignition | On fuse block. | |
| Fuel Pump In-Line Fuse | On right side of firewall, behind battery junction block cover. (Scheme 4) | |
| Fuse Block | ||
| 4.3L | Under left side of dash, near kick panel. (Scheme 6) | |
| 5.7L | Under left side of dash, near kick panel. (Scheme 1) | |
| 7.4L - 1989 | Under left side of dash, near kick panel. (Scheme 2) | |
| 7.4L - 1990 | Under left side of dash, near kick panel. (Scheme 3) | |
| Fusible Links | ||
| Air Conditioning (Rust) | On right side of firewall, at battery junction block. (Scheme 4) | |
| A/T Kickdown Sol. (Red) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Aux. Battery Relay (Rust) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Aux. Cooling Fan Relay (Gray) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Charging System (Blue) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Diesel ECM (Gray) | On right side of firewall, at battery junction block. (Scheme 4) | |
| ECM (Gray) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Fuse Block (Black) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Glow Plug Controller (Blue) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Instrument Panel (Black) | On right side of firewall, at battery junction block. (Scheme 4) | |
| Junction Block (Diesel) (Blue) | On positive battery cable, below battery. | |
| Junction Block (Gas) (Red) | On positive battery cable, below battery. | |
CIRCUIT PROTECTION DEVICES LOCATION
CONTROL UNITS
| Component | Location | |
|---|---|---|
| Check Engine Light Driver Module (Diesel Only) | Under right side of dash, above blower motor. (Scheme 7) | |
| Cruise Control Module | On left side of firewall, near brake booster. (Scheme 8) | |
| Electronic Control Module (ECM) | ||
| 4.3L | Behind right side of dash, above blower motor. (Scheme 6) | |
| 5.7L | Behind right side of dash, above blower motor. (Scheme 1) | |
| 7.4L - 1989 | Behind right side of dash, above blower motor. (Scheme 2) | |
| 7.4L - 1990 | Behind right side of dash, above blower motor. (Scheme 3) | |
| Right Side Of Dash | Behind right side of dash, above blower motor. (Scheme 7) | |
| Electronic Spark Control (ESC) | ||
| 4.3L | On right side of engine, above valve cover. (Scheme 6) | |
| 5.7L | On right side of engine, above valve cover. (Scheme 1) | |
| 4.3L Component View | On right side of engine, above valve cover. (Scheme 9) | |
| 5.0L & 5.7L Component View | On right side of engine, above valve cover. (Scheme 10) | |
| Diesel Electronic Control Module (DECM) | Behind right side of dash, above blower motor. (Scheme 7) | |
| Hot Fuel Handling Module (5.7L H/D) | Behind right side of Instrument Panel above Blower Motor. (Scheme 1) | |
| Glow Plug Controller (6.2L) | On left rear of intake manifold. | |
| Low Coolant Module (6.2L) | On center of firewall. | |
| Rear Anti-Lock Brake Module | On bracket, left of master cylinder. (Scheme 8) | |
CONTROL UNITS LOCATION
SENDING UNITS & SENSORS
| Component | Location | ||
|---|---|---|---|
| Cold Advance Control (CAC) & Fast Idle Solenoid Temp. Sensor (6.2L) | On rear of right cylinder head. | ||
| Coolant Temperature Sensor | |||
| 4.3L | In front of intake manifold, at thermostat housing. (Scheme 6) | ||
| 5.0L & 5.7L | On right front of engine, in front of valve cover. (Scheme 1) | ||
| 6.2L | On right front of intake manifold. | ||
| 7.4L - 1989 | On right front of intake manifold, near thermostat housing. (Scheme 2) | ||
| 7.4L - 1990 | On right front of intake manifold, near thermostat housing. (Scheme 3) | ||
| Coolant Temp. Sending Unit/Switch | In left cylinder head. | ||
| Engine Speed Sensor (6.2L) | On rear of intake manifold. | ||
| Knock Sensor | |||
| 4.3L | On lower left side of engine, under exhaust manifold. | ||
| 4.3L | On lower right side of engine, under exhaust manifold. (Scheme 6) | ||
| 5.7L | On lower right side of engine, under exhaust manifold. (Scheme 1) | ||
| 5.0L & 5.7L Component View | On lower right side of engine, under exhaust manifold. (Scheme 10) | ||
| Manifold Absolute Pressure (MAP) Sensor | |||
| Diesel | On left side of firewall, near wiper motor. | ||
| Gas | |||
| 4.3L | On right side of engine, above valve cover. (Scheme 6) | ||
| 5.7L | On right side of engine, above valve cover. (Scheme 1) | ||
| 7.4L - 1989 | On right side of engine, above valve cover. (Scheme 2) | ||
| 7.4L - 1990 | On right side of engine, above valve cover. (Scheme 3) | ||
| 4.3L Component View | On right side of engine, above valve cover. (Scheme 9) | ||
| 5.0 & 5.7L Component View | On right side of engine, above valve cover. (Scheme 10) | ||
| 7.4L Component View | On right side of engine, above valve cover. (Scheme 11) | ||
| Oil Pressure Sending Unit/Switch | |||
| Diesel | On left rear of engine. | ||
| Gas | |||
| 4.3L | On left side of engine, under exhaust manifold. (Scheme 6) | ||
| 5.7L | On left side of engine, under exhaust manifold. (Scheme 1) | ||
| 7.4L - 1989 | On left side of engine, under exhaust manifold. (Scheme 2) | ||
| 7.4L - 1990 | On left side of engine, under exhaust manifold. (Scheme 3) | ||
| Oxygen (O2) Sensor | |||
| 4.3L | In exhaust manifold or header pipe. (Scheme 6) | ||
| 5.7L | In exhaust manifold or header pipe. (Scheme 1) | ||
| 7.4L - 1989 | In exhaust manifold or header pipe. (Scheme 2) | ||
| 7.4L - 1990 | In exhaust manifold or header pipe. (Scheme 3) | ||
| Throttle Position Sensor (TPS) | |||
| Diesel | On injection pump throttle valve. | ||
| Gasoline | |||
| 4.3L | On throttle body. (Scheme 6) | ||
| 5.7L | On throttle body. (Scheme 1) | ||
| 7.4L - 1989 | On throttle body. (Scheme 2) | ||
| 7.4L - 1990 | On throttle body. (Scheme 3) | ||
| 4.3L Component View | On throttle body. (Scheme 9) | ||
| 5.0L & 5.7L Component View | On throttle body. (Scheme 10) | ||
| 7.4L Component View | On throttle body. (Scheme 11) | ||
| Vehicle Speed Sensor (VSS) | |||
| 4.3L (2WD) | On right side of extension housing. (Scheme 6) | ||
| 4.3L (4WD) | On right side of transfer case. (Scheme 6) | ||
| 5.7L (2WD) | On right side of extension housing. (Scheme 1) | ||
| 5.7L (4WD) | On right side of transfer case. (Scheme 1) | ||
| 7.4L - 1989 (2WD) | On right side of extension housing. (Scheme 2) | ||
| 7.4L - 1989 (4WD) | On right side of transfer case. (Scheme 2) | ||
| 7.4L - 1990 (2WD) | On right side of extension housing. (Scheme 3) | ||
| 7.4L - 1990 (4WD) | On right side of transfer case. (Scheme 3) | ||
SENDING UNITS & SENSORS LOCATION
MOTORS
| Component | Location |
|---|---|
| A/C-Heater Blower Motor | Behind right side of dash. (Scheme 7) |
| A/C-Heater Door Motor | On plenum, behind right side of dash. |
| Windshield Wiper Motor | In plenum, on left center of firewall. |
MOTORS LOCATION
SOLENOIDS & SOLENOID VALVES
| Component | Location | |
|---|---|---|
| A/T Downshift Solenoid | On left side of transmission, in front of vehicle speed sensor. | |
| Cold Advance Solenoid (6.2L) | On injection pump, on left front of engine. | |
| EGR Pulse Solenoid Valve (6.2L) | On top of engine, near left valve cover. | |
| EGR Vacuum Solenoid | ||
| 4.3L | On right side of engine, above valve cover. (Scheme 6) | |
| 5.7L | On right side of engine, above valve cover. (Scheme 1) | |
| 5.0 & 5.7L Component View | On right side of engine, above valve cover. (Scheme 10) | |
| 6.2L | On top left of engine, near left valve cover. | |
| 7.4L - 1989 | On top of engine, on left valve cover. (Scheme 2) | |
| 7.4L - 1990 | On top of engine, on left valve cover. (Scheme 3) | |
| Elec. Air Control (EAC) Solenoid | ||
| 4.3L | On right front of engine, near air pump. (Scheme 6) | |
| 5.7L | On right front of engine, near air pump. (Scheme 1) | |
| 7.4L - 1989 | On right front of engine, near air pump. (Scheme 2) | |
| 7.4L - 1990 | On right front of engine, near air pump. (Scheme 3) | |
| 4.3L Component View | On right front of engine, near air pump. (Scheme 9) | |
| 5.0 & 5.7L Component View | On right front of engine, near air pump. (Scheme 10) | |
| 7.4L Component View | On right front of engine, near air pump. (Scheme 11) | |
| Exhaust Pressure Regulator (EPR) Solenoid Valve (6.2L) | On top left rear of engine. | |
| Fast Idle Solenoid (6.2L) | On injection pump, on left front of engine. | |
| Front Axle Solenoid | On right side of differential case. | |
| Fuel Shutoff Solenoid (6.2L) | On injection pump, on left front of engine. | |
| Idle Air Control (IAC) Valve | ||
| 4.3L | On right side of throttle body. (Scheme 6) | |
| 5.7L | On right side of throttle body. (Scheme 1) | |
| 7.4L - 1989 | On right side of throttle body. (Scheme 2) | |
| 7.4L - 1990 | On right side of throttle body. (Scheme 3) | |
| 4.3L Component View | On right side of throttle body. (Scheme 9) | |
| 5.0L & 5.7L Component View | On right side of throttle body. (Scheme 10) | |
| 7.4L Component View | On right side of throttle body. (Scheme 11) | |
| Rear Anti-Lock Brake Valve | Below master cylinder. (Scheme 8) | |
| Torque Conv. Clutch (TCC) Solenoid | ||
| 4.3L | In automatic transmission. (Scheme 6) | |
| 5.7L | In automatic transmission. (Scheme 1) | |
SOLENOIDS & SOLENOID VALVES LOCATION
SWITCHES
| Component | Location | |
|---|---|---|
| A/C Air Inlet Press. Switch | ||
| 5.0L & 5.7L Component View | On rear of A/C compressor. (Scheme 10) | |
| 7.4L Component View | On rear of A/C compressor. (Scheme 11) | |
| A/C Pressure Cycling Switch | ||
| 4.3L Component View | On accumulator. (Scheme 9) | |
| 5.0 & 5.7L Component View | On accumulator. (Scheme 10) | |
| 7.4L Component View | On accumulator. (Scheme 11) | |
| Back-Up Light Switch (M/T) | On left side of transmission. | |
| Brake Pressure (Warning) Switch | In hydraulic brake combination valve. | |
| Brake/Stoplight Switch | On brake pedal bracket. | |
| Clutch/Neutral Safety Switch | On clutch pedal bracket. | |
| Cooling Fan Temp. Switch (7.4L) | In right cylinder head, above exhaust manifold. (Scheme 11) | |
| Cruise Control Release Switch | On brake pedal bracket. | |
| Front Axle Switch | Near differential case, at front of engine. | |
| Fuel Pump/Oil Pressure Switch | ||
| 4.3L | On left rear of engine, near distributor. (Scheme 6) | |
| 5.0L & 5.7L | On left rear of engine block. (Scheme 1) | |
| 7.4L - 1989 | On left side of engine block, under exhaust manifold. (Scheme 2) | |
| 7.4L - 1990 | On left side of engine block, under exhaust manifold. (Scheme 3) | |
| Headlight Dimmer Switch | On left side of steering column, behind dash. | |
| Inhibit Switch | On right side of firewall, near accumulator. | |
| Low Coolant Switch | In top of radiator. | |
| Parking Brake Switch | On parking brake pedal bracket. | |
| Park/Neutral Switch | On steering column, under dash | |
| TCC Brake Switch | On brake pedal bracket. | |
| TCC Governor Pressure Switch | In automatic transmission. | |
| Transfer Case Switch | On left front of transfer case. | |
SWITCHES LOCATION
MISCELLANEOUS
| Component | Location | |
|---|---|---|
| A/C Compressor Clutch Diode | In A/C compressor clutch connector. | |
| A/C-Heater Blower Resistor | On evaporator case, in engine compartment. | |
| ALDL Diagnostic Connector | ||
| 4.3L | Under left side of dash, to left of column. (Scheme 6) | |
| 5.7L | Under left side of dash, to left of column. (Scheme 1) | |
| 7.4L - 1989 | Under left side of dash, to left of column. (Scheme 2) | |
| 7.4L - 1990 | Under left side of dash, to left of column. (Scheme 3) | |
| Battery Junction Block | On right side of firewall, behind cover. (Scheme 4) | |
| Convenience Center | Under left side of dash, left of steering column. (Scheme 5) | |
| Front Axle Actuator | Below front of right exhaust manifold. | |
| Fuel Heater/Water Detector (6.2L) | On top right side of engine. | |
| Fuel Pump (Gas) | In fuel tank. | |
| Fuel Pump (Diesel) | On left frame rail. | |
| Fuel Pump Prime/Test Connector | ||
| 4.3L | On right side of firewall, near battery junction block. (Scheme 6) | |
| 5.7L | On right side of firewall, near battery junction block. (Scheme 1) | |
| 7.4L - 1989 | On right side of firewall, near battery junction block. (Scheme 2) | |
| 7.4L - 1990 | On right side of firewall, near battery junction block. (Scheme 3) | |
| Rear Anti-Lock Brake In-Line Diode | Under left side of dash, near convenience center. | |
| TCC In-Line Resistor | Under right side of dash, under blower motor. (Scheme 7) | |
MISCELLANEOUS LOCATION
COMPONENT LOCATION GRAPHICS
Note. Figures may show multiple component locations. Refer to appropriate table for proper figure references.
