Engine Controls - Basic Testing: Diagnosis Lexus LS II

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. See VACUUM DIAGRAMS article to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

MECHANICAL INSPECTION

Using Scan Tool

1. Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 36) Turn ignition on. DO NOT start engine.
2. Using scan tool manufacturer's instructions, activate electric fuel pump. Listen for fuel pump operating sound and feel for pressure in fuel line near fuel filter. Turn ignition off. Remove scan tool. If fuel pump operates, check fuel pressure. See FUEL PRESSURE.
3. If fuel pump does not operate, EFI main relay, circuit opening relay or fuel pump relay (if used) may be defective. See «SYSTEM/COMPONENT TESTS»(ref-22208) article.
4. If relays are okay, check wiring circuit and fuses. If fuel pump does not operate, check for defective fuel pump or defective fuel pump ground. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-22206) article.

Scheme 36

SPARK TEST

Note. LS400 haS 2 distributors and 2 ignition coils. Distributors are located at front end of each cylinder head, under cover.

1. Remove No. 3 (upper) timing belt covers to access distributors. 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 not present, go to next step. If spark is present at coil wire but not at spark plug wire, replace faulty distributor rotor, cap, wires or spark plugs as necessary.
2. Turn ignition off. Check for poor electrical connections at ignition coil, ignitor and distributor. Repair as necessary. If connections are okay, check resistance of coil wire and spark plug wires. Maximum allowable resistance is 25,000 ohms per wire.
3. If resistance is okay, turn ignition on. Disconnect ignition coil connector. Measure voltage between ground and positive terminal at ignition coil connector. See IGNITION COIL POSITIVE TERMINAL IDENTIFICATION table. If battery voltage is not present, check for open or grounded wire between battery and ignition coil or open fuse, also check for faulty ignition main relay).
4. If battery voltage is present, turn ignition off. Measure ignition coil resistance. To measure primary resistance, measure resistance between terminals of ignition coil. To measure secondary resistance, measure resistance between positive wire terminal at ignition coil and coil secondary tower. If resistance is not as specified, replace ignition coil. See IGNITION COIL RESISTANCE table. IGNITION COIL POSITIVE TERMINAL IDENTIFICATION Application Wire Color LS400 Black/Red IGNITION COIL RESISTANCE Application Primary Secondary LS400 Cold (1).36-.55 9000-15,400 Hot (2).45-.65 11,400-18,100 (1) Coil temperature of 14-122°F (-10-50°C). (2) Coil temperature of 123-212°F (51-100°C).
5. If resistance is as specified, check resistance across terminals of the following distributor sensor. Camshaft Position (CMP) sensor and Crankshaft Position (CKP) sensor. (Scheme 37)
6. If resistance is not as specified, replace CKP sensor. See DISTRIBUTOR SENSOR RESISTANCE table. If resistance is as specified, go to step 8).
7. Check ignition IGT signal from Engine Control Module (ECM). If IGT signal from ECM is defective a Diagnostic Trouble Code (DTC) should set in ECM memory. See testing procedure for DTC P1305 in «TESTS W/CODES»(ref-22204) article. If IGT signal circuit is okay, substitute another ignitor and recheck system operation.

DISTRIBUTOR SENSOR (1) RESISTANCE

Scheme 37

Scheme 38