Engine Controls - Basic Testing Lexus ES V20

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no start condition.

The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

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.

COMPRESSION CHECK

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.

EXHAUST SYSTEM BACKPRESSURE CHECK

The exhaust system can be checked with a vacuum or pressure gauge. Remove O2 sensor. Connect a 1-10 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4-2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction.

Scheme 1

Scheme 2

Scheme 3

1. Ensure battery voltage is at least 11 volts with engine off. If battery voltage is not to specification, replace battery. If battery voltage is to specification, go to next step.
2. Crank engine. If engine cranks, go to next step. If engine does not crank, see in DIAGNOSIS BY SYMPTOM in TESTS W/O CODES article.
3. Start engine. If engine starts, go to next step. If engine does not start, go to step 12).
4. Remove air filter. Inspect air filter for excessive dirt and oil. Replace if necessary. Reinstall air filter if okay and go to next step.
5. Check air intake system between airflow meter and cylinder head for air leaks. If air leaks are found, repair as necessary. If no air leaks are found, go to next step.
6. Check idle speed. Start and warm engine to operating temperature. Place transmission in Neutral. Turn off all accessories. Connect a tachometer to terminal IG- of check connector. For location of check connector (Scheme 1)
7. See IDLE SPEED SPECIFICATIONS table. If idle speed is okay, go to next step. If idle speed is not within specification, see DIAGNOSIS BY SYMPTOM in TESTS W/O CODES article. CAUTION: DO NOT ground check connector terminal IG-. Damage to ignitor and/or ignition coil may result. NOTE: Ensure tachometer is compatible with this system before use. IDLE SPEED SPECIFICATIONS Application RPM ES250 650-750
8. Check ignition timing. Start and warm engine to operating temperature. Ensure idle speed is within specification. Using a jumper wire, connect check connector terminals E1 and TE1. (Scheme 3)
9. Connect timing light to No. 1 cylinder. Check ignition timing. See IGNITION TIMING SPECIFICATIONS table. IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM) Application Specification ES250 10 @ 650-750
10. Disconnect jumper wire from check connector. With transmission in Neutral, timing should move within a range of approximately 13-27 degrees BTDC.
11. If ignition timing is not within specification, loosen distributor hold-down bolts and adjust as necessary.
12. If ignition timing is within specification and a normal code is displayed by CHECK engine light, see DIAGNOSIS BY SYMPTOM in TESTS W/O CODES article. If a code is displayed by CHECK engine light, see appropriate code chart.
13. Ensure throttle valve is fully closed. Ensure continuity is present between Throttle Position Sensor (TPS) terminals IDL and E2. (Scheme 2) Ensure engine valve timing is correct. WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel injection-related component. DO NOT allow fuel to contact engine or electrical components.
14. Check fuel pressure. Ensure a sufficient amount of fuel is in fuel tank. Turn ignition off. Using a jumper wire, connect check connector terminals +B and FP. (Scheme 3) Turn ignition on.
15. Using fingers, ensure fuel pressure is felt in hose from fuel filter. When fuel system is pressurized, fuel return noise will also be heard. Turn ignition off.
16. If no fuel pressure was felt, check fusible links, fuses (EFI 15-amp and IGN 7.5-amp), EFI main relay, fuel pump, ECU and wiring connections. CAUTION: SLOWLY loosen cold start injector fuel line to avoid fuel spraying onto skin, eyes and vehicle finish.
17. Connect fuel pressure gauge to cold start injector fuel line. Using a jumper wire, connect terminals FP and +B of check connector. (Scheme 3) Turn ignition on. Check fuel pressure.
18. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is more than specification, replace fuel pressure regulator. If fuel pressure is less than specification, check fuel hoses, hose connections, fuel pump, fuel filter and fuel pressure regulator. FUEL PRESSURE SPECIFICATIONS Application psi (kg/cm 2 ) Ignition On, Engine Off 38-44 (2.7-3.1) Engine Idling (1) 38-44 (2.7-3.1) Engine Idling (2) 33-37 (2.3-2.6) Ignition Off, Engine Off 21 (1.5) (1) With fuel pressure regulator vacuum hose disconnected. (2) With fuel pressure regulator vacuum hose connected. CAUTION: DO NOT confuse check connector terminal connection as this may create additional malfunctions.
19. Start engine. Disconnect and plug vacuum hose from fuel pressure regulator. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS table. Unplug and reconnect vacuum hose to fuel pressure regulator.
20. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is not within specification, check fuel pressure regulator and vacuum hose.
21. Turn engine off. Ensure fuel pressure does not drop less than specified value for 5 minutes after engine is turned off. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is not as specified, check fuel pump, fuel pressure regulator and fuel injectors. Remove fuel pressure gauge.
22. On all models, check for spark. Remove coil wire from distributor. Using insulated pliers, hold end of coil wire 1/2" from ground. Crank engine. If spark is present, see DIAGNOSIS BY SYMPTOM in appropriate TESTS W/O CODES article. If spark is not present, see SPARK TEST in this article.

Scheme 4

Scheme 5

1. Turn ignition off. Check ignition coil, ignitor and distributor connectors. Repair as necessary. If connectors are okay, go to next step.
2. Using an ohmmeter, check resistance of high tension cables. Maximum resistance allowed is 25,000 ohms per cable. Replace as necessary. If resistance is within specification, go to next step.
3. Turn ignition on. Using a DVOM, ensure battery voltage is present at ignition coil positive terminal. If battery voltage is not present, check wiring between ignition switch and ignition coil. If battery voltage is present, go to next step.
4. Turn ignition off. Using a DVOM, measure resistance of ignition coil (cold). Primary resistance is.41-.50 ohm. Positive terminal on ignition coil has a tab next to terminal. Secondary resistance is 10,200-13,800 ohms. If resistance is not within specification, replace ignition coil. If resistance is within specification, go to next step.
5. Measure resistance of pick-up coil. (Scheme 4) Measure resistance between terminals G1 and G-, G2 and G-, and NE and G-. Resistance should be 140-180 ohms. If resistance is not within specification, replace distributor housing assembly.
6. Check air gap in distributor. Measure air gap of G1 pick-up, G2 pick-up and NE pick-up. (Scheme 5) Air gap specification is.008" (.20 mm). If air gap is not to specification, replace distributor.
7. Perform CODE 14 (step 9) trouble shooting procedures for ES250. See TESTS W/CODES article. If voltage reading and wire harness are okay, try another ignitor.

SUMMARY

If no faults were found while performing BASIC TESTING , proceed to G - TEST W/CODES article. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.