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.
Spark Test (GS400, LS400 & SC400)
1998 Lexus GS 300SECTION Spark Test (GS400, LS400 & SC400)
CAUTION:
To prevent fuel from being injected during cranking in the following procedure, crank engine for no more than 5-10 seconds at a time.
- Disconnect ignition coil connector. Disconnect injector connector for cylinder being tested. Remove ignition coil to be checked. Remove spark plug. Connect spark plug to coil and reconnect ignition coil connector. Ground the spark plug.
- Check plug for spark while cranking engine. If spark is not present, turn ignition off. Check ignition coil and ignitor connectors. Repair as necessary. If connections are good, substitute another ignition coil with ignitor and recheck system operation.
- If problem persists, turn ignition on. Using a voltmeter, check for battery voltage between ground and positive terminal (Black/White wire on GS400 and SC400 or Black/Red wire on LS400) at ignition coil connector.
- If battery voltage is not present, repair circuit between ignition switch and ignition coil or ignitor. If battery voltage is present, check resistance between terminals of Camshaft Position (CMP) sensor. See SENSOR RESISTANCE table. If resistance is not as specified, replace CMP sensor. If resistance is as specified, check resistance between terminals of Crankshaft Position (CKP) sensor. See SENSOR RESISTANCE table.
- If resistance is not as specified, replace CKP sensor. If resistance is as specified, check for ignitor circuit malfunction (IGT signal). If IGT signal from ECM is defective a Diagnostic Trouble Code (DTC) should set in ECM memory. See testing procedure for DTC P1300 in TESTS W/CODES article. If IGT signal circuit is okay, substitute another ignition coil with ignitor and recheck system operation.
IGNITION COIL RESISTANCE
| Application | Primary | Secondary | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Aisan (3) | |||||||||
| Cold (1) | .70-.94 | 10,800-14,900 | |||||||
| Hot (2) | .85-1.10 | 13,100-17,500 | |||||||
| Diamond (3) | |||||||||
| Cold (1) | .70-.94 | 6,800-11,700 | |||||||
| Hot (2) | .85-1.10 | 8,600-13,700 | |||||||
|
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IGNITION COIL RESISTANCE
| Application | Primary | Secondary | ||||
|---|---|---|---|---|---|---|
| Cold (1) | .33-.52 | 8,500-14,700 | ||||
| Hot (2) | .42-.61 | 10,800-17,200 | ||||
|
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SENSOR RESISTANCE
| Application | Ohms | |||||
|---|---|---|---|---|---|---|
| Camshaft Sensor | ||||||
| Cold (1) | 835-1400 | |||||
| Hot (2) | 1060-1645 | |||||
| Crankshaft Sensor | ||||||
| Cold (1) | 1630-2740 | |||||
| Hot (2) | 2065-3225 | |||||
|
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RENDER: 1.0x
NO RELATED
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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.