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 Lexus ES 250 AutomaticFACTORY OEM SERVICE PROCEDURE
Starter Relay Test
NOTE:
Starter relays are part of the theft deterrent system. When the theft deterrent system is activated, a contact inside the theft deterrent ECU is opened. This creates an open circuit on the ground side of the starter relay, thus making the starter inoperative. Use steps 3) and 4) of starter relay testing procedure to check theft deterrent system starter cut-out (if necessary). Unlock driver's door with key to cancel starter cut-out BEFORE checking starter relay circuit.
- Locate and remove starter relay from left, rear corner of engine compartment. Ensure continuity exists between terminals No. 1 and No. 3. See Fig 1. No continuity should exist between terminals No. 2 and No. 4. If continuity is not as specified, replace relay.
- Apply battery voltage across terminals No. 1 and No. 3. Continuity should now exist between terminals No. 2 and No. 4. If continuity is not as specified, replace relay.
- Locate theft deterrent ECU behind glove box and disconnect connectors. See Figure. Turn ignition switch to ST (start) position. With shift lever in Neutral or clutch pedal depressed, check voltage between terminal No. 18 of theft deterrent ECU wiring harness connector and body ground.
- If voltage does not exist, check and repair harness/connections between starter relay and theft deterrent ECU. If voltage exists and starter relay circuit is still inoperative, test and replace theft deterrent ECU.
Factory Service Tools
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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.
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