Symptom Confirmation And Diagnostic Trouble Code
HINT:
The diagnostic system in LEXUS GX470 has various functions. The first function is the Diagnostic Trouble Code (DTC) Check, in which a malfunction in the signal circuits to the ECU is stored in code form in the ECU memory. Another function is the Input Signal Check, which checks if the signals from various switches are sent to the ECU correctly. By using these check functions, it is possible to quickly narrow down potential problem areas and troubleshooting can be performed effectively. The diagnostic functions are incorporated in the following systems in LEXUS GX470.
| System | Diagnostic Trouble Code Check | Input Signal Check (Sensor Check) | Diagnostic Test Mode (Active Test) |
|---|---|---|---|
| SFI System | CIRCLE (with Check Mode) | CIRCLE | CIRCLE |
| Electronic Modulated Suspension & Rear Air Suspension System | CIRCLE | CIRCLE | CIRCLE |
| Kinetic Dynamic Suspension System | CIRCLE | CIRCLE | CIRCLE |
| ABS with EBD & BA & TRAC & VSC System | CIRCLE | CIRCLE | CIRCLE |
| Electronically Controlled Automatic Transmission [ECT] | CIRCLE (with Check Mode) | CIRCLE | - |
| Power Tilt and Power Telescopic Steering Column | CIRCLE | CIRCLE | CIRCLE |
| Air Conditioning System | CIRCLE | CIRCLE | - |
| Supplemental Restraint System | CIRCLE | - | - |
| Engine Immobiliser System | CIRCLE | - | CIRCLE |
| Multiplex Communication System | CIRCLE | - | - |
| Cruise Control System | CIRCLE | CIRCLE | - |
- In the DTC check, it is very important to determine whether the problem indicated by the DTC is still occurring or has occurred in the past but returned to normal at present. In addition during the problem symptom check it must be checked whether the malfunction indicated by the DTC is directly related to the problem symptom or not. For this reason, the DTC should be checked before and after symptom confirmation to determine the current conditions. If this is not done, it may, depending on the case, result in unnecessary troubleshooting for normally operating systems, making it more difficult to detect the problem area, or in trying to repair irrelevant areas. Therefore, always follow the procedures in the correct order and perform the DTC check.
- A flow chart showing how to proceed with troubleshooting using the diagnostic trouble code (DTC) . This flow chart shows how to utilize the DTC check effectively. Then, by carefully checking the results, this chart indicates how to proceed either to the DTC troubleshooting or to the troubleshooting of the problem symptoms table.
- DTC check
- Go to next step.
- Make a note of DTCs displayed and then clear the memory
- Go to next step.
- Symptom confirmation SYMPTOM CONFIRMATION
a Symptoms exist b No symptoms exist - Go to step 5
- Go to next step.
- Simulation test using the symptom simulation methods
- Go to next step.
- DTC check DTC CHECKING REFERENCE
a DTC displayed b Normal code displayed - a: Troubleshooting of problem indicated by DTC
- b: Go to next step
- Symptom confirmation SYMPTOM CONFIRMATION
a No symptoms exist b Symptoms exist If a DTC is displayed in the initial DTC check, it indicates that a trouble may have occurred in a wire harness or connector in that circuit in the past. Therefore, check the wire harness and connectors (See ELECTRONIC CIRCUIT INSPECTION PROCEDURE ).
- a: System normal
- b: Go to next step
Troubleshooting of each problem symptom
The problem is still occurring in a place other than the diagnostic circuit (The DTC displayed first is either for a past problem or a secondary problem).