Diagnostic Aids
WARNING: This page is about a different car, the 2003 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
- Sensor 1 refers to sensor closest to engine body.
- After confirming DTCs P2195, P2196, P2197 and P2198, use OBD-II scan tool or hand-held tester to confirm voltage output of A/F sensor (AFS 131 S1/AFS B2 S1) from "DIAGNOSIS/ENHANCED OBD-II/DATA LIST/ALL DATA".
- Air/fuel ratio sensors output voltage and short-term fuel trim value can be read using OBD-II scan tool or hand-held tester.
- ECM controls voltage of AFR+, AFL+, AFR- and AFL- terminals of ECM to fixed voltage. Therefore, it is impossible to confirm air/fuel ratio sensor output voltage without OBD-II scan tool or hand-held tester.
- OBD-II scan tool displays one/fifth of air/fuel ratio sensor output voltage which is displayed on hand-held tester.
- Using the hand-held tester only, it is possible to narrow down trouble area by performing ACTIVE TEST of "A/F CONTROL" (oxygen sensor or another can be distinguished). "A/F CONTROL" is an ACTIVE TEST which changes injection volume to -12.5 percent or +25 percent.
- Connect the hand-held tester to DLC3. See Figure.
- Turn ignition switch on.
- Warm up the engine with engine speed at 2500 RPM for approximately 90 seconds.
- Select item "DIAGNOSIS/ENHANCED OBD-II/ACTIVE TEST/AF CONTROL".
- Perform "A/F CONTROL" in idle condition (press right or left button).
- There is a few second delay in sensor 1 (front air/fuel ratio sensor) output. There is about a 20 second delay in sensor 2 (rear oxygen sensor). Air/fuel ratio sensor and oxygen sensor react synchronized with increase and decrease of injection volume (+25 percent to rich output: one volt, -12.5 percent to lean output: zero volts). See Fig 1.
- To display graph indication, select and push "YES or NO" button 2 data "AFS B1S1 and O2S B1S2" or "AFS B2S1 and O2S B2S2" and press button "4" after selecting "ACTIVE TEST/AF CONTROL/USER DATA".
- Read freeze frame data using hand-held tester or OBD-II scan tool, as freeze frame data records engine conditions when a malfunction is detected. When troubleshooting, it is useful to determine whether vehicle was running or stopped, engine was warmed up or not, air-fuel ratio was lean or rich, etc. at time of malfunction.