Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Problem Symptoms Table
PROBLEM SYMPTOMS TABLE
HINT:
- Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
- Inspect the fuses and relays related to this system before inspecting the suspected areas below.
| Symptom | Suspected Area | Link |
|---|---|---|
| Engine does not crank (Does not start) | Battery | |
| ST relay | | |
| Starter assembly | | |
| Starter signal circuit | | |
| Smart access system with push-button start (for start function) | | |
| VC output circuit (ECM 5 V output) | | |
| Park/neutral position switch assembly (for 2WD models) | | |
| Park/neutral position switch assembly (for AWD models) | | |
| No initial combustion (Does not start) | Immobiliser system | |
| ECM power source circuit | | |
| VC output circuit (ECM 5 V output) | | |
| Ignition system | | |
| Fuel pump control circuit | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Crankshaft position sensor | | |
| Intake system | | |
| Valve timing | | |
| No. 1 valve rocker arm sub-assembly* | | |
| Engine cranks normally but difficult to start | ECM power source circuit | |
| Flow chart [Engine difficult to start] | | |
| Throttle body with motor assembly | | |
| Fuel pump assembly (for high pressure side) | | |
| Fuel pump (for low pressure side)(for TMC made) | | |
| Fuel pump (for low pressure side)(for TMMC made) | | |
| Engine coolant temperature sensor | | |
| Fuel pump control circuit | | |
| Ignition system | | |
| Spark plug | | |
| Compression | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Crankshaft position sensor | | |
| Intake system | | |
| Valve timing | | |
| No. 1 valve rocker arm sub-assembly* | | |
| Incomplete intermittent combustion occurs (Does not start) | Fuel pump control circuit | |
| Ignition system | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Crankshaft position sensor | | |
| Intake system | | |
| Valve timing | | |
| High engine speed | Throttle body with motor assembly | |
| ECM power source circuit | | |
| PCV hose | | |
| PCV system | | |
| Low engine speed (Poor idle) | Fuel pump control circuit | |
| Throttle body with motor assembly | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Fuel pump assembly (for high pressure side) | | |
| PCV hose | | |
| PCV system | | |
| Intake system | | |
| Rough idle | Flow chart [Rough idling] | |
| Throttle body with motor assembly | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Fuel pump assembly (for high pressure side) | | |
| Ignition system | | |
| Compression | | |
| Fuel pump control circuit | | |
| Spark plug | | |
| Intake system | | |
| Valve timing | | |
| No. 1 valve rocker arm sub-assembly* | | |
| Hunting (Poor idle) | Throttle body with motor assembly | |
| ECM power source circuit | | |
| Fuel pump control circuit | | |
| Spark plug | | |
| Intake system | | |
| Drive start control | | |
| Hesitation/Poor acceleration (Poor driveability) | Fuel injector assembly (for port injection) | |
| Fuel injector assembly (for direct injection) | | |
| Fuel pump control circuit | | |
| Fuel pump assembly (for high pressure side) | | |
| Ignition system | | |
| Spark plug | | |
| Intake system | | |
| Valve timing | | |
| No. 1 valve rocker arm sub-assembly* | | |
| Brake override system | | |
| Drive start control | | |
| Lack of power | Flow chart [Lack of power] | |
| Surging (Poor driveability) | Fuel pump control circuit | |
| Spark plug | | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| No. 1 valve rocker arm sub-assembly* | | |
| Engine stalls soon after starting | Flow chart [Engine stalls] | |
| Fuel pump control circuit | | |
| Throttle body with motor assembly | | |
| Crankshaft position sensor | | |
| Ignition system | | |
| Fuel pump assembly (for high pressure side) | | |
| Intake system | | |
| Valve timing | | |
| Engine stalls soon after slow down | Flow chart [Engine stalls] | |
| Fuel injector assembly (for port injection) | | |
| Fuel injector assembly (for direct injection) | | |
| Throttle body with motor assembly | | |
| ECM | | |
| Crankshaft position sensor | | |
| Ignition system | | |
| Unable/difficult to refuel | Fuel system (canister, refueling valve, roll over valve, fuel tank, etc.) | - |
| Drive mode does not change | Drive mode select switch circuit | |
HINT:
*: Check "Fuel Cut Elapsed Time" in the Data List. If the elapsed time is over 0 sec, then the engine speed is high (the engine speed at which fuel cut occurs + 500 rpm or more). In this situation, there is a possibility that a No. 1 valve rocker arm sub-assembly will become loose and malfunction, check that the No. 1 valve rocker arm sub-assemblies are properly installed.
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Readiness Monitor Drive Pattern
READINESS MONITOR DRIVE PATTERN PURPOSE OF READINESS TESTS
The On-Board Diagnostic (OBD II) system is designed to monitor the performance of emission related components, and indicate any detected a ...
Diagnosis System
DIAGNOSIS SYSTEM DESCRIPTION When troubleshooting OBD II (On-Board Diagnostics) vehicles, the Techstream (complying with SAE J1978) must be connected to the DLC3 (Data Link Connector 3) of the vehicl ...
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual
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Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual
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