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.
1990 Geo Tracker Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Output Signals
NOTE:
Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation on each output component, refer to the system indicated in brackets after component.
The ECM processes information from the input signals and sends appropriate voltage control signals to the following engine controls:
- A/C Vacuum Switching Valve (Fuel System)
- Automatic Transmission Lock-Up Relay (Miscellaneous Controls)
- CHECK ENGINE Light (Self-Diagnostic System)
- Circuit Opening Relay (Fuel System)
- Control Relay (Fuel System)
- Distributor Ignitor (Ignition System)
- EFI Main Relay (Fuel System)
- EGR Vacuum Switching Valve (Emission Systems)
- Fuel-Cut System (Fuel System)
- Fuel Injector (Fuel System)
- Fuel Pressure Regulator Vacuum Switching Valve Fuel System)
- Fuel Pump Relay (Fuel System)
- Idle Air Control (IAC) Valve (Fuel System)
- Idle Speed Control (ISC) Solenoid (Fuel System)
- Idle Speed Control (ISC) Valve (Fuel System)
- Idle-Up Vacuum Switching Valve (IVSV) (Fuel System)
- Ignition Coil (Ignition System)
- Positive Temperature Coefficient (PTC) Heater Relay (Emission Systems)
- Secondary Air Vacuum Switching Valve (SEC-VSV) Air Induction System)
- Shift Indicator Light (Miscellaneous Controls)
- Throttle Opener Vacuum Switching Valve (Fuel System)
Factory Service Tools
Use the Manual With the Right Hardware
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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.