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.
1993 Lexus LS 400FACTORY OEM SERVICE PROCEDURE
Spark Test
NOTE:
LS400 and SC400 have 2 distributors and 2 ignition coils. Distributors are located at front end of each cylinder head, under cover.
- Disconnect coil wire from distributor(s). Using insulated pliers, hold end of coil wire 1/2" from ground. Crank engine for 1-2 seconds. If spark is present, see appropriate DIAGNOSIS BY SYMPTOM in TROUBLE SHOOTING - NO CODES article.
- If spark is not present, turn ignition off. Check ignition coil, ignitor and distributor connectors. Repair as necessary.
- If connectors are okay, check resistance of high tension cables. Maximum resistance is 25,000 ohms per cable. Replace as necessary. If resistance is within specification, go to next step.
- Turn ignition on. Disconnect ignition coil connector. Check voltage at ignition coil positive wire terminal (White/Red wire terminal on ES300; Black/Orange wire terminal on all others). If battery voltage is not present, check wiring between ignition switch and ignition coil.
- If battery voltage is present, turn ignition off. Measure ignition coil resistance (cold). See IGNITION COIL RESISTANCE table. If resistance is not within specification, replace ignition coil.
- If resistance is within specification, check resistance across terminals of appropriate distributor sensor (distributor pick-up coil, camshaft sensors, crankshaft sensor, etc.). See Fig 1-4. See DISTRIBUTOR SENSOR RESISTANCE table.NOTE: Crankshaft sensor may also be called engine speed sensor.
- If resistance is not within specification, replace appropriate component (distributor housing, camshaft sensor or crankshaft sensor). If resistance is within specification, go to next step (ES300, GS300 and SC300), or go to step 9) (LS400 or SC400).
- Measure air gap of pick-up coils G1, G2 and NE. See Fig 4. See DISTRIBUTOR PICK-UP COIL AIR GAP table. If air gap is within specification, go to next step. If air gap is not within specification, replace distributor.
- Check ignition signal from ECM to ignitor. See procedure for Code 14 (and Code 15 on LS400 and SC400) in SELF-DIAGNOSTICS article. If ignition signal and its circuit are okay, replace ignitor.
IGNITION COIL RESISTANCE
| Application | Primary | Secondary | |
|---|---|---|---|
| ES300 | .30-.60 | 9000-15,000 | |
| GS300 | |||
| Cold | .21-.33 | 6400-11,100 | |
| Hot | .27-.39 | 8200-13,000 | |
| LS400 | |||
| Cold | .36-.55 | 9,000-15,400 | |
| Hot | .45-.65 | 11,400-18,100 | |
| SC300 | .20-.30 | 6000-11,000 | |
| SC400 | .40-.50 | 10,000-14,000 | |
DISTRIBUTOR SENSOR RESISTANCE
| Application | Ohms | ||
|---|---|---|---|
| ES300 (Pick-Up Coils) | |||
| Between Terminals G1 & "G" | 125-190 | ||
| Between Terminals G2 & "G" | 125-190 | ||
| Between Terminals NE & "G" | 155-240 | ||
| GS300 (Pick-Up Coils) | |||
| Cold | |||
| Between Terminals G1 & "G" | 125-200 | ||
| Between Terminals G2 & "G" | 125-200 | ||
| Between Terminals NE & "G" | 155-200 | ||
| Hot | |||
| Between Terminals G1 & "G" | 160-235 | ||
| Between Terminals G2 & "G" | 160-235 | ||
| Between Terminals NE & "G" | 190-290 | ||
| SC300 (Pick-Up Coils) | |||
| Between Terminals G1 & "G" | 125-190 | ||
| Between Terminals G2 & "G" | 125-190 | ||
| Between Terminals NE & "G" | 155-240 | ||
| LS400 (Camshaft Sensors & Crankshaft Sensor) | |||
| Cold | 835-1400 | ||
| Hot | 1060-1645 | ||
| SC400 (Camshaft Sensors & Crankshaft Sensor) | 835-1350 | ||
DISTRIBUTOR PICK-UP COIL AIR GAP (1)
| Application | In. (mm) | ||
|---|---|---|---|
| ES300 & GS300 | .008-.020 (.20-.50) | ||
| SC300 | .008-.016 (.20-.40) | ||
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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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