BUZZERS, RELAYS & TIMERS
| Component | Location | |
|---|---|---|
| A/C-Heater Blower Relay | On evaporator case, in engine compartment. | |
| Auxiliary Cooling Fan Relay | On right side of firewall. (Scheme 1) | |
| Cold Advance Control Relay (Diesel) | On right side of firewall. | |
| Downshift Relay 3L80 (THM 400) | ||
| Component View | On right side of firewall. (Scheme 1) | |
| 4.3L | On right side of firewall. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | On right side of firewall. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | On right side of firewall. (Scheme 4) | |
| 7.4L - 1989 | On right side of firewall. (Scheme 5) | |
| 7.4L - 1990 | On right side of firewall. (Scheme 6) | |
| Fuel Pump Relay | ||
| Component View | On right side of firewall. (Scheme 1) | |
| 4.3L | On right side of firewall. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | On right side of firewall. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | On right side of firewall. (Scheme 4) | |
| 7.4L - 1989 | On right side of firewall. (Scheme 5) | |
| 7.4L - 1990 | On right side of firewall. (Scheme 6) | |
| Hazard Flasher Relay | Under left side of dash. | |
| Horn Relay | Behind left side of dash, on harness near fuse block. | |
| Power Door Lock Delay Relay | Behind left side of dash, above kick panel. | |
| Power Door Lock Relay | Behind left side of dash, above kick panel. | |
| Turn Signal Flasher Relay | On fuse block. | |
BUZZERS, RELAYS & TIMERS LOCATION
CIRCUIT PROTECTION DEVICES
| Component | Location | |
|---|---|---|
| Battery Junction Block (1989 ONLY) | On left side of firewall. | |
| Circuit Breakers | ||
| Headlight/Parking Light | In headlight switch. | |
| Power Door Lock | On fuse block. | |
| Power Window | On fuse block. | |
| Rear A/C | On firewall. | |
| Convenience Center | Under left side of dash. | |
| Fuse Block | ||
| 4.3L | Under left side of dash. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | Under left side of dash. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | Under left side of dash. (Scheme 4) | |
| 7.4L - 1989 | Under left side of dash. (Scheme 5) | |
| 7.4L - 1990 | Under left side of dash. (Scheme 6) | |
| Fusible Links | ||
| A/C-Heater (Red) | At battery junction block (rear unit). | |
| Alternator (Rust) | At battery junction block. | |
| Auxiliary Cooling Fan Relay (Rust) | At battery junction block. | |
| Glow Plug Controller (Rust) (Diesel) | At starter solenoid. | |
| Ignition Switch (Rust) | At battery junction block (2 links). | |
| Power Accessories (Rust) | At battery junction block. | |
CIRCUIT PROTECTION DEVICES LOCATION
CONTROL UNITS
| Component | Location | |
|---|---|---|
| Audio Alarm Module | On bracket, to left of steering column. | |
| Cruise Control Module | On brake pedal bracket. | |
| Electronic Control Module (ECM) | ||
| 4.3L | Under driver's seat. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | Under driver's seat. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | Under driver's seat. (Scheme 4) | |
| 7.4L - 1989 | Under driver's seat. (Scheme 5) | |
| 7.4L - 1990 | Under driver's seat. (Scheme 6) | |
| Elect. Spark Control (ESC) Module | ||
| 4.3L | Under driver's seat. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | Under driver's seat. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | Under driver's seat. (Scheme 4) | |
| Glow Plug Controller (Diesel) | ||
| Diesel Component View | On left rear of intake manifold. (Scheme 7) | |
| Diesel Engine Component View | On left rear of intake manifold. (Scheme 8) | |
| Hot Fuel Handling Module | ||
| 5.0L & 5.7L - 1989 | Under driver's seat. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | Under driver's seat. (Scheme 4) | |
| 7.4L - 1989 | Under driver's seat. (Scheme 5) | |
| 7.4L - 1990 | Under driver's seat. (Scheme 6) | |
| Hydro-Boost Elect. Delay Module | Behind left side of instrument panel. | |
| Light Driver Module (Diesel) | Under right side of dash. | |
| Power Door Lock Delay Module | Above left kick panel. | |
| Pulse Wiper Control Module | Taped to harness, at right side of steering column. | |
| RWAL Elect. Control Unit | In engine compartment on bracket attached to master cylinder. | |
CONTROL UNITS LOCATION
SENDING UNITS & SENSORS
| Component | Location | ||
|---|---|---|---|
| Coolant Level Sensor | In radiator. | ||
| Coolant Temp. Sending Unit/Switch | On left cylinder head. (Scheme 8) | ||
| Coolant Temperature Sensor | |||
| Diesel Engine | On front of intake manifold. (Scheme 8) | ||
| 4.3L | On front of intake manifold. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | On front of intake manifold. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | On front of intake manifold. (Scheme 4) | ||
| 7.4L - 1989 | On front of intake manifold. (Scheme 5) | ||
| 7.4L - 1990 | On front of intake manifold. (Scheme 6) | ||
| Engine Speed Sensor (Diesel) | On right rear of engine. | ||
| Fuel Pressure Sensor (Diesel) | In fuel filter assembly. (Scheme 8) | ||
| Knock Sensor | |||
| 4.3L | On left cylinder head. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | On lower left side of engine block, above starter. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | On lower left side of engine block, above starter. (Scheme 4) | ||
| 7.4L | |||
| 1989 | On right side of engine block, above starter. | ||
| 1990 | On right side of engine block, above starter. (Scheme 6) | ||
| MAP Sensor (Diesel) | On right side of firewall. | ||
| MAP Sensor (Gas) | |||
| 4.3L | On bracket, at center of right valve cover. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | On bracket, at center of right valve cover. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | On bracket, at center of right valve cover. (Scheme 4) | ||
| 7.4L - 1989 | On bracket, at center of right valve cover. (Scheme 5) | ||
| 7.4L - 1990 | On bracket, at center of right valve cover. (Scheme 6) | ||
| Oil Pressure Sending Unit/Switch | |||
| Diesel | On engine block, behind left cylinder head. (Scheme 8) | ||
| Gas | |||
| 4.3L | On left side of engine block, above oil filter. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | On left side of engine block, above oil filter. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | On left side of engine block, above oil filter. (Scheme 4) | ||
| 7.4L - 1989 | On left side of engine block, above oil filter. (Scheme 5) | ||
| 7.4L - 1990 | On left side of engine block, above oil filter. (Scheme 6) | ||
| Oxygen Sensor | |||
| 4.3L | In exhaust manifold. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | In exhaust manifold. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | In exhaust manifold. (Scheme 4) | ||
| 7.4L - 1989 | In exhaust manifold. (Scheme 5) | ||
| 7.4L - 1990 | In exhaust manifold. (Scheme 6) | ||
| Throttle Position Sensor (TPS) | |||
| 4.3L | On throttle linkage. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | On throttle linkage. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | On throttle linkage. (Scheme 4) | ||
| 7.4L - 1989 | On throttle linkage. (Scheme 5) | ||
| 7.4L - 1990 | On throttle linkage. (Scheme 6) | ||
| Vehicle Speed Sensor (VSS) | |||
| 4.3L | At right top of engine. (Scheme 2) | ||
| 5.0L & 5.7L - 1989 | At right top of engine. (Scheme 3) | ||
| 5.0L & 5.7L - 1990 | In dash, behind speedometer. (Scheme 4) | ||
| 7.4L - 1989 | At right top of engine. (Scheme 5) | ||
| 7.4L - 1990 | In dash, behind speedometer. (Scheme 6) | ||
| Water-In-Fuel Sensor (Diesel) | In fuel filter assembly. (Scheme 8) | ||
SENDING UNITS & SENSORS LOCATION
MOTORS
| Component | Location | |
|---|---|---|
| A/C-Heater Blower Motor | On right side of firewall. | |
| Idle Air Control (IAC) Motor | ||
| 4.3L | On throttle body. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | On throttle body. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | On throttle body. (Scheme 4) | |
| 7.4L - 1989 | On throttle body. (Scheme 5) | |
| 7.4L - 1990 | On throttle body. (Scheme 6) | |
| Power Door Lock Motor | At rear, in each door. | |
| Power Window Motor | At center, in each door. | |
| Windshield Washer Motor | On windshield washer reservoir. | |
| Windshield Wiper Motor | On firewall. | |
MOTORS LOCATION
SOLENOIDS & SOLENOID VALVES
| Component | Location | |
|---|---|---|
| Canister Purge Solenoid Valve | On vapor canister, or in vapor hose. | |
| Cold Advance Solenoid (Diesel) | On injection pump. | |
| Electrical Sir Control (EAC) Solenoid | ||
| 4.3L (V8) | Behind air pump, on right front of engine. (Scheme 2) | |
| 4.3L (V6) | Behind air pump, on right rear of engine. (Scheme 2) | |
| 5.0L & 5.7L (V8) - 1989 | Behind air pump, on right front of engine. (Scheme 3) | |
| 5.0L & 5.7L (V6) - 1989 | Behind air pump, on right rear of engine. (Scheme 3) | |
| 5.0L & 5.7L (V8) - 1990 | Behind air pump, on right front of engine. (Scheme 4) | |
| 5.0L & 5.7L (V6) - 1990 | Behind air pump, on right rear of engine. (Scheme 4) | |
| 7.4L (V8) - 1989 | Behind air pump, on right front of engine. (Scheme 5) | |
| 7.4L (V6) - 1990 | Behind air pump, on right rear of engine. (Scheme 6) | |
| EGR Dump Solenoid (Diesel) | On top left rear of engine. (Scheme 7) | |
| EGR/EPR Solenoids (Diesel) | On top left rear of engine. (Scheme 7) | |
| EGR Vacuum Solenoid (Gas) | ||
| 4.3L | At right top of engine. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | At right top of engine. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | At right top of engine. (Scheme 4) | |
| 7.4L - 1989 | At right top of engine. (Scheme 5) | |
| 7.4L - 1990 | At right top of engine. (Scheme 6) | |
| Fast Idle Solenoid (Diesel) | On injection pump. | |
| Fuel Shutoff Solenoid (Diesel) | At top center of engine, near intake plenum. | |
| Torque Conv. Clutch (TCC) Solenoid | ||
| 5.0L & 5.7L | In automatic transmission. (Scheme 3) | |
| 7.4L - 1989 | In automatic transmission. (Scheme 5) | |
| 7.4L - 1990 | In automatic transmission. (Scheme 4) | |
SOLENOIDS & SOLENOID VALVES LOCATION
SWITCHES
| Component | Location |
|---|---|
| A/C Pressure Cycling Switch | On rear of accumulator. |
| Auxiliary Fan Temp. Switch | In right cylinder head. |
| Back-Up Light Switch (A/T) | At base of steering column. |
| Back-Up Light Switch (M/T) | On left side of transmission. |
| Brake Pressure Warning Switch | On proportioning valve, at left frame rail. |
| Clutch Switch (Cruise) (M/T) | On clutch pedal bracket. |
| Coolant Temperature Switch | In left cylinder head. |
| Fuel Pump/Oil Press. Switch | On rear of intake manifold. |
| Glow Plug Inhibit Switch (Diesel) | On front of engine. |
| Hydro-Boost Flow Switch | In pressure line, at power steering pump. |
| Hydro-Boost Press. Warning Switch | In pressure line, behind master cylinder. |
| Stoplight Switch | On brake pedal bracket. |
| Throttle Position Switch (Diesel) | On fuel injection pump. |
| Transmission Kickdown Switch | At top of accelerator pedal bracket. |
SWITCHES LOCATION
MISCELLANEOUS
| Component | Location | |
|---|---|---|
| A/C-Heater Blower Resistors | On evaporator case, in engine compartment. | |
| ALDL Diagnostic Connector | ||
| 4.3L | Under left side of dash. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | Under left side of dash. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | Under left side of dash. (Scheme 4) | |
| 7.4L - 1989 | Under left side of dash. (Scheme 5) | |
| 7.4L - 1990 | Under left side of dash. (Scheme 6) | |
| Cruise Control Servo (1989 ONLY) | On bracket, on right side of engine. | |
| Fuel Heater (Diesel) | At fuel filter. (Scheme 8) | |
| Fuel Pump Prime/Test Connector | ||
| 4.3L | On firewall, next to fuel pump relay. (Scheme 2) | |
| 5.0L & 5.7L - 1989 | On firewall, next to fuel pump relay. (Scheme 3) | |
| 5.0L & 5.7L - 1990 | On firewall, next to fuel pump relay. (Scheme 4) | |
| 7.4L - 1989 | On firewall, next to fuel pump relay. (Scheme 5) | |
| 7.4L - 1990 | On firewall, next to fuel pump relay. (Scheme 6) | |
| Hydro-Boost In-Line Diode | In harness, behind instrument panel. | |
| Set Timing Connector (Gas) | In harness, near distributor. | |
| Tachometer Connector | In harness, at ignition coil. | |
| Vehicle Speed Sensor (VSS) Buffer | Taped to harness, behind instrument panel. | |
MISCELLANEOUS LOCATION
COMPONENT LOCATION GRAPHICS
Note. Figures may show multiple component locations. Refer to appropriate table for proper figure references.
