Displaying & Reading Trouble Codes
NOTE: This is the only information provided by the manufacturer for reading Diagnostic Trouble Codes for this system.1. DIAGNOSIS SYSTEM
a. Description
When troubleshooting OBD II vehicles, the only difference from the usual troubleshooting procedure is that you connect an OBD II scan tool complying with SAE J1987 or TOYOTA hand-held tester to the vehicle, and read off various data output from the vehicle's ECM.
OBD II regulations require that the vehicle's on-board computer lights up the Malfunction Indicator Lamp (MIL) on the instrument panel when the computer detects a malfunction in the computer itself or in drive system components which affect vehicle emissions In addition to the MIL lighting up when a malfunction is detected, the applicable DTCs prescribed by SAE J2012 are recorded in the ECM memory.
If the malfunction only occurs in 3-trip, the MIL goes off but the DTCs remain recorded in the ECM memory.
To check the DTCs, connect an OBD II scan tool or TOYOTA hand-held tester to DLC3 on the vehicle The OBD II scan tool or TOYOTA hand-held tester also enables you to erase the DTCs and check freeze frame data and various forms of engine data (For instruction book).
DTCs include SAE controlled codes and Manufacturer controlled codes.
SAE controlled codes must be set as the codes prescribed by the SAE, while Manufacturer controlled codes can be set freely by the manufacturer within the prescribed limits.
The diagnosis system operates in normal mode during normal vehicle use, and also has a check mode for technicians to simulate malfunction symptoms and perform troubleshooting. Most DTCs use 2-trip detection logic(*) to prevent erroneous detection. By switching the ECM to check mode when troubleshooting, the technician can cause the MIL to light up and for a malfunction that is only detected once or momentarily (TOYOTA hand-held tester).
* 2-trip detection logic:
When a logic malfunction is first detected, the malfunction is temporarily stored in the ECM memory. If the same malfunction is detected again during the 2nd test drive, this 2nd detection causes the MIL to light up
b. Inspect the DLC3.
The vehicle's ECM uses the V.P.W. (Variable Pulse Width) for communication to comply with SAE J1850. The terminal arrangement of DLC3 complies with SAE J1962 and matches the V.P.W. format.
HINT: If your display shows "UNABLE TO CONNECT TO VEHICLE" when you have connected the cable of OBD II scan tool or TOYOTA hand-held tester to DLC3, turned the ignition switch ON and operated the scan tool, there is a problem on the vehicle side or tool side.
If communication is normal when the tool is connected to another vehicle, inspect DLC3 on the original vehicle.
If communication is still not possible when the tool is connected to another vehicle, the problem is probably in the tool itself, so consult the Service Department listed in the tool's instruction manual.
2. INSPECT DIAGNOSIS (NORMAL MODE)
a. Check the MIL.
1. The MIL comes on when the ignition switch is turned ON and the engine is not running.
HINT: If the MIL does not light up, troubleshoot the combination meter.
2. When the engine is started, the MIL should go off. If the lamp remains on, the diagnosis system has detected a malfunction or abnormality in the system.
b. Check the DTC.
NOTE: TOYOTA hand-held tester only: When the diagnostic system is switched from normal mode to check mode, it erases all DTCs and freeze frame data recorded in normal mode. So before switching modes, always check the DTCs and freeze frame data, and note them down.
1. Prepare an OBD II scan tool (complying with SAE J1978) or TOYOTA hand-held tester.
2. Connect the OBD II scan tool or TOYOTA hand- held tester to DLC3 at the lower of the instrument panel.
3. Turn the ignition switch ON and turn the OBD II scan tool or TOYOTA hand-held tester switch ON.
4. Use the OBD II scan tool or TOYOTA hand-held tester to check the DTCs and freeze frame data and note them down (For operating instructions, see the OBD II scan tool's instruction book).
5. See Trouble Code Descriptions to confirm the details of the DTCs.
NOTE: When simulating symptoms with an OBD II scan tool (excluding TOYOTA hand-held tester) to check the DTCs, use normal mode. For codes on the DTCs chart subject to "2 trip detection logic", turn the ignition switch off after the symptoms have been simulated the 1st time. Then repeat the simulation process again. When the program has DTCs, the DTCs are recorded in the ECM.
3. INSPECT DIAGNOSIS (CHECK MODE)
HINT: TOYOTA hand-held tester only:
Compared to the normal mode, the check mode has high sensing ability to detect malfunctions. Furthermore, the same diagnostic items which are detected in Normal mode can also be detected in Check mode.
a. Check the DTC.
1. Check the initial conditions.
- Battery positive voltage 11 V or more.
- Throttle valve fully closed. Transmission in P position.
- Air conditioning switched off.
2. Turn the ignition switch OFF.
3. Prepare a TOYOTA hand-held tester.
4. Connect the TOYOTA hand-held tester to DLC3 at the lower side of the instrument panel
5. Turn the ignition switch ON and switch the TOYOTA hand-held tester ON.
6. Switch the TOYOTA hand-held tester from Normal mode to Check mode (Check that the MIL flashes).
7. Start the engine (MIL goes out after the engine starts).
8. Simulate the conditions of the malfunction described by the customer.
NOTE: Leave the ignition switch ON until you have checked the DTCs, etc.
9. After simulating the malfunction conditions, use the TOYOTA hand-held tester diagnosis selector to check the DTCs and freeze frame data, etc.
HINT: Take care not to turn the ignition switch OFF, as turning it off the diagnosis system switches from Check mode to Normal mode, so all DTCs, etc. are erased.
10. After checking the DTC, inspect the applicable circuit.