DTCs are output as either 5-digit or 2-digit codes. In the Repair Manual, the detection item, detecting condition and trouble area are included for each DTC, so refer to the Repair Manual when troubleshooting.
1. 5-digit DTCs
For 5-digit DTCs, connect the hand-held tester to DLC3 to communicate directly with the engine ECU and display the DTC on the tester screen for confirmation.
2. 2-digit DTCs
Confirm 2-digit DTCs by observing the MIL blinking pattern. Short between terminals TE1 (Tc) – E1 (CG) of DLC1 (Data Link Connector 1), DLC2 or DLC3 to make the MIL blink and output the DTC. Confirm the DTC using the blinking pattern of the lamp.
In the event of tow or more malfunction codes, indication will begin from the smaller numbered code and continue in order to the larger.
To short between the terminals, use the diagnosis check wire (SST: 09843- 18020 or 09843-18040).
On some vehicles with DLC3, it is not possible to output 2-digit DTCs.
There are also some models where 2-digit DTCs can be checked using a handheld tester. Connect the hand-held tester to the DLC and read the MIL blinking pattern to confirm the 2-digit DTC on the tester screen.
Terminal VF Output
Terminal VF is the terminal that outputs the engine ECU data.
Terminal VF outputs the following data.
1. Air-fuel ratio feedback corrective value
Output is normally fixed at 2.5 V, but a 5 V output provides feedback that the amount of fuel is being increased, so it is possible that the air-fuel ratio has become lean. Conversely, a 0 V output provides feedback that the amount of fuel is being decreased, so it is possible that the air-fuel ratio has become rich. However it is necessary to pay attention for 0 V output when the engine does not meet the conditions of the feedback such as a cold engine.
2. Oxygen sensor signal
When shorted terminals TE1 and E1, and set the throttle position sensor (IDL) contact to off, the output the oxygen sensor signal is 5 V for a rich signal and 0 V for a lean signal. However, if the feedback control is not operating, 0 V is standard.
3. Diagnosis results
When shorted terminal TE1 and E1 (IDL contact is on), 5 V is output if the diagnosis results are normal, or 0 V if a DTC has been stored.
The engine ECU records DTCs using a constant power supply, so DTCs are not cleared when the ignition switch is turned to off. Accordingly, in order to clear DTCs, it is necessary to use a hand-held tester to communicate with the engine ECU and clear the DTCs, or remove the EFI fuse or battery cable to cut off the constant engine ECU power supply. However, care is required, because cutting off the constant engine ECU power supply also clears the learning values recorded in the engine ECU memory.
The hand-held tester communicates with the engine ECU, enabling it to do the following in addition to DTCoutput and clearing.
Check the freeze frame data.
Check the data monitored by the engine ECU.
Perform an active test that forces the actuators to drive
Diagnostic Mode Selection Function
The diagnostic system has two modes: Normal mode and check mode.
1. Normal mode
Use this mode for normal diagnosis.
2. Check mode
This mode provides higher diagnostic detection sensitivity than normal mode and makes it easier to detect malfunctions. It is easier to detect DTCs in this mode when performing malfunction reproduction tests on the vehicle. All DTCs and the freeze frame data will be cleared at this mode.
There are two types for the check mode: By switching from normal mode when using a hand-held tester to communicate with the engine ECU, or by switching from normal mode when using TE1 and TE2 on the DLC.