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.
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HOMESERVICE MANUALSLEXUS1999RX 300 AWD V6-3.0L (1MZ-FE)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTSERVICE PRECAUTIONSELECTRONIC CONTROL SYSTEM
1999 Lexus RX 300 AWD V6-3.0L (1MZ-FE)
Electronic Control System
1999 Lexus RX 300 AWD V6-3.0L (1MZ-FE)SECTION Electronic Control System
1. BEFORE WORKING ON FUEL SYSTEM, DISCONNECT NEGATIVE (-) TERMINAL CABLE FROM BATTERY
HINT: Any diagnostic trouble code retained by the computer will be erased when the negative (-) terminal cable is removed from the battery. Therefore, if necessary, read the diagnosis before removing the terminal.
2. DO NOT SMOKE OR WORK NEAR AN OPEN FLAME WHEN WORKING ON FUEL SYSTEM
3. KEEP GASOLINE AWAY FROM RUBBER OR LEATHER PARTS
4. ELECTRONIC CONTROL SYSTEM
a. Before removing SFI wiring connectors, terminals, etc., first disconnect the power by either turning the ignition switch OFF or disconnecting the negative (-) terminal cable from the battery.
HINT: Always check the diagnostic trouble code before disconnecting the negative (-) terminal cable from the battery.
b. When installing the battery, be especially careful not to incorrectly connect the positive (+) and negative (-) cable.
c. Do not permit parts to receive a severe impact removal or installation. Handle all SFI parts carefully, especially the ECM.
d. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact can further troubles.
e. Do not open the ECM cover.
f. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment, prevent water from getting on the SFI parts and wiring connectors.
g. Parts should be replaced as an assembly.
h. Care is required when pulling out and inserting wiring connectors.
1. Release the lock and pull out the connector, pulling on the connectors.
2. Fully insert the connector and check that it is locked.
i. When inspecting a connector with a volt/ohmmeter
1. Carefully take out the water-proofing rubber if it is a water-proof type connector.
2. Insert the test probe into the connector from the wiring side when checking the continuity, amperage or voltage.
3. Do not apply unnecessary force to the terminal.
4. After checking, install the water-proofing rubber on the connector securely.
j. Use SST for inspection or test of the injector or its wiring connector.
SST 09842-30070
HINT: Any diagnostic trouble code retained by the computer will be erased when the negative (-) terminal cable is removed from the battery. Therefore, if necessary, read the diagnosis before removing the terminal.
2. DO NOT SMOKE OR WORK NEAR AN OPEN FLAME WHEN WORKING ON FUEL SYSTEM
3. KEEP GASOLINE AWAY FROM RUBBER OR LEATHER PARTS
4. ELECTRONIC CONTROL SYSTEM
a. Before removing SFI wiring connectors, terminals, etc., first disconnect the power by either turning the ignition switch OFF or disconnecting the negative (-) terminal cable from the battery.
HINT: Always check the diagnostic trouble code before disconnecting the negative (-) terminal cable from the battery.
b. When installing the battery, be especially careful not to incorrectly connect the positive (+) and negative (-) cable.
c. Do not permit parts to receive a severe impact removal or installation. Handle all SFI parts carefully, especially the ECM.
d. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact can further troubles.
e. Do not open the ECM cover.
f. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment, prevent water from getting on the SFI parts and wiring connectors.
g. Parts should be replaced as an assembly.
h. Care is required when pulling out and inserting wiring connectors.
1. Release the lock and pull out the connector, pulling on the connectors.
2. Fully insert the connector and check that it is locked.
i. When inspecting a connector with a volt/ohmmeter
1. Carefully take out the water-proofing rubber if it is a water-proof type connector.
2. Insert the test probe into the connector from the wiring side when checking the continuity, amperage or voltage.
3. Do not apply unnecessary force to the terminal.
4. After checking, install the water-proofing rubber on the connector securely.
j. Use SST for inspection or test of the injector or its wiring connector.
SST 09842-30070
RENDER: 1.0x
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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.