DTC 25

DTC 25 - Air/Fuel Ratio Lean Malfunction
DTC 26 - Air/Fuel Ratio Rich Malfunction





CIRCUIT DESCRIPTION
The main oxygen sensor is located in the exhaust manifold.
It indirectly determines whether the fuel mixture is rich or lean by detecting the concentration of oxygen present in the exhaust gas.

WIRING DIAGRAM





DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern:
- To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
- To check that the malfunction is corrected when the repair is completed confirming that diagnostic trouble code is no longer detected.

Malfunction: Open or Short in Main Oxygen Sensor
Open or Short in Injector Circuit, Injector Leak or Blockage.

HINTS: ^ Before this test, check the feedback voltage for oxygen sensor.
^ If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.




1. Disconnect the "EFI" fuse (15 A) for 10 seconds or more, with IG switched OFF.
2. Initiate test mode (Connect terminal TE2 and E1 of data link connector 1 (DLC1) with IG switched OFF).
3. Start engine and warm it up.
4. Race the engine at 2,500 rpm for 3 minutes.
5. Let the engine idle for 1 minute.
- If a malfunction exists, the Malfunction Indicator Lamp will light up during step (5).

INSPECTION PROCEDURE