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 L4-1590cc 1.6LFACTORY OEM SERVICE PROCEDURE
ECM Circuit Resistance Check
ECM RESISTANCE CHECK
CAUTION: To prevent ECM damage, disconnect the negative battery cable before removal or installation of ECM connectors. Check the resistance with the connectors disconnected at the ECM, and ignition switch "OFF." If any of the following circuits are shorted, a new ECM could become damaged.
Fuel Injector:
Between Pin G8 and Pin G17 1-2 Ohms
ISC Solenoid Valve:
Between Pin G6 and Pin G15 5-7 Ohms
Lock-up relay and PTC heater relay (for A/T vehicle):
Between Pin Y10 and Pin Y11 180-220 Ohms
EGR VSV and throttle opener VSV:
Between Pin G5 and Pin G14 70-80 Ohms
Control Relay [1]:
Between ECM connector terminal G16 (Pink) and terminal circuit 440 (BLK/WHT) of control relay, with connectors connected. See ECM Electrical Diagrams. Diagrams
Between Pin G16 and circuit 440 114-140 Ohms
NOTE:
[1] Control relay/ECM wiring is the same with either Automatic or Manual transmission.
ECM VOLTAGE CHECK
See ECM Connector Pin Out chart to check ECM Pin voltage. [1][2]Diagrams
CAUTION: To prevent ECM damage, disconnect the negative battery cable before removal or installation of ECM connectors. Check the resistance with the connectors disconnected at the ECM, and ignition switch "OFF." If any of the following circuits are shorted, a new ECM could become damaged.
Fuel Injector:
Between Pin G8 and Pin G17 1-2 Ohms
ISC Solenoid Valve:
Between Pin G6 and Pin G15 5-7 Ohms
Lock-up relay and PTC heater relay (for A/T vehicle):
Between Pin Y10 and Pin Y11 180-220 Ohms
EGR VSV and throttle opener VSV:
Between Pin G5 and Pin G14 70-80 Ohms
Control Relay [1]:
Between ECM connector terminal G16 (Pink) and terminal circuit 440 (BLK/WHT) of control relay, with connectors connected. See ECM Electrical Diagrams. Diagrams
Between Pin G16 and circuit 440 114-140 Ohms
NOTE:
[1] Control relay/ECM wiring is the same with either Automatic or Manual transmission.
ECM VOLTAGE CHECK
See ECM Connector Pin Out chart to check ECM Pin voltage. [1][2]Diagrams
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.