DTCs P0300-P0306 Detection Logic
On DTCs P0300-P0306, MIL is set in 2 stages. If ECM detects misfiring strong enough to cause catalytic converter overheating for 200 consecutive engine revolutions, MIL will blink, but will not stay illuminated. If the ECM detects misfiring strong enough to cause deterioration of catalytic converter during 2 consecutive drive cycles for 1000 consecutive engine revolutions, MIL will illuminate.
Note. When road testing vehicle in CHECK mode (Lexus scan tool only), the Two Trip Detection Logic will not function. Also, MIL will illuminate first time a malfunction is detected.
DATA LINK CONNECTOR
OBD-II regulations standardize Data Link Connector (DLC) configurations. On all models, DLC No. 3 connector is located under left side of instrument panel. (Scheme 37)
Scheme 37
FREEZE-FRAME DATA
The ECM records engine operating condition when a misfire, fuel trim (mixture) malfunction or other malfunction (fuel system, calculated load, coolant temperature, fuel trim (mixture), engine speed, vehicle speed, etc.) exists. If more than one fault is detected, only data from the first malfunction is recorded. Recorded data is useful for determining conditions in which the malfunction occurs.
NORMAL Mode Code Retrieval
- Connect scan tool to Data Link Connector (DLC) No. 3. (Scheme 37) DLC No. 3 is located under left side of instrument panel. Turn ignition on with engine off. Turn scan tool on. Using scan tool manufacturer's instructions, check for DTCs and freeze-frame data.
- Record any DTCs and freeze-frame data displayed for system diagnosis. If driveability problem exists and no DTCs are present, go to «TROUBLE SHOOTING - NO CODES»(ref-134942) article for diagnosis by symptom.
- If any DTCs are present, perform appropriate diagnostic test. See «DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION»(ref-134935-S06152497012002022100000) table. For more information on freeze-frame data, see «FREEZE-FRAME DATA»(ref-134935-S25196165712002022100000) under INTRODUCTION. For information on 2-trip detection logic codes, see «TWO-TRIP DETECTION LOGIC»(ref-134935-S21353108092002022100000) under INTRODUCTION.
- After repairs for DTC have been completed, DTCs must be cleared from ECM memory. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-134935-S34521729992002022100000).
SUMMARY
If no diagnostic trouble codes are present, driveability symptoms exist or intermittents exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent procedures.
Confirmation Driving Pattern
Switch hand-held tester from normal mode to check mode. Start engine and let engine idle for 100 seconds or more. Drive vehicle at 24 mph or more for 20 seconds for more. Let engine idle for 20 seconds or more. Repeat procedure 3 times. Let engine idle for 30 seconds. Check oxygen sensor output voltage. If a malfunction exists, CHECK ENGINE warning light should come on.