OBD II Readiness Monitors

Monitor Status

Helping set Monitors

First, make sure that the check engine light is not commanded on. Having stored DTC faults or even pending diagnostic trouble codes active may prevent a monitor from running to completion.

Second, make sure that you have enough fuel in the car. Some monitors, for instance the EVAP monitor, may require the fuel level to be between 35% and 85% to enable the monitor to execute.

Third, complete the drive cycle.

EVAP Drive Cycles
The following are sample drive cycles for the EVAP monitor:

Ford: With fuel tank one half to three-quarters full, cruise at 45 to 65 mph for 10 minutes. Avoid sharp turns and hills during this period.

Chrysler: There are two-parts to this test. The first part runs after idling for five minutes, then driving at 30 to 45 mph for two minutes (fuel tank must be half to 85 percent full). The second part runs after the vehicle has sit for 8 or more hours (cold soak) without being driven. Start the engine and idle for four minutes, then drive in stop-and-go traffic for five minutes using smooth accelerations and decelerations. Stop and idle for 4 minutes. The EVAP monitor should be complete.

An example of some common enabling criteria to run the EVAP monitors drive cycle:

  • The malfunction indicator lamp (MIL) must be off
  • Barometric pressure exceeds 75 Kpa
  • At start-up, IAT and ECT is between 45°F and 85°F
  • IAT is not more than 2°F greater than ECT
  • ECT is not more than 12°F greater than IAT
  • Fuel tank level is between 26 percent and 74 percent
  • The TPS is between 9 percent and 35 percent
  • The EVAP solenoid is at 50 percent pulse width PWM, within 65 seconds of engine run time

Oxygen Sensor Drive Cycles
The following are some sample drive cycle requirements for the oxygen sensor monitor to run:

Ford: The monitor should run when the engine has reached normal operating temperature, the inlet air temperature is between 40 and 100 degrees F, and the vehicle is cruising at a steady 40 mph for four minutes.

GM: GM uses a two-part oxygen sensor monitor. The first part of the monitor runs after idling the engine for two and a half minutes with the A/C and rear defroster on. This checks the sensor heater circuit. After this, turn the A/C and defroster off, then accelerate at half throttle to 55 mph and hold at a steady 55 mph for three minutes. This will complete the second half of the monitor that checks the responsiveness of the O2 sensors.

Chrysler: Idle for five minutes (to reach closed loop operation). Then drive at a steady vehicle speed above 25 mph for two minutes. Stop and idle for 30 seconds. Then smoothly accelerate to 30 to 40 mph. Repeat the last two steps five times.

Toyota: The oxygen sensor monitor should run after idling the engine for nine minutes, then driving at a steady 25 mph for two minutes.

Catalytic Converter Drive Cycles
The catalytic converter monitor may require specific driving conditions before it will run. Depending on the vehicle application, this usually includes completing the oxygen sensor monitors first, followed by driving at highway speeds (60 to 65 mph) for at least 10 to 15 minutes under light load, no conflicts with other monitors that have not yet run (such as EVAP or EGR monitors which may have to complete before the catalyst monitor will run), and no fault codes that could affect the accuracy of the test. Some vehicles have very specific drive cycles that must be followed before the catalyst monitor will run. In some cases, it may even be necessary to complete the prescribed drive cycle several times before the catalyst monitor will run.

The following are some sample drive cycles for the catalyst monitor to run.

Ford: The catalytic converter monitor will not run until the oxygen sensor monitor has run and completed successfully with no faults found. The vehicle must then be driven in stop-and-go traffic conditions at five different cruise speeds ranging from 25 to 45 mph over a period of 10 minutes.

GM: The catalytic converter monitor runs after cruising at 55 mph for 5 minutes, but it may take up to five drive cycles at this speed before the monitor will run.

Chrysler: The catalytic converter monitor will not run unless the Check Engine light is off, no pending codes are present, the fuel level is between 15 and 85 percent full, and the coolant temperature is above 70 degrees F. If these conditions have been met, the engine must have run at least 90 seconds, and the engine speed must be between 1,350 and 1,900 rpm. Idle vehicle for five minutes (to reach closed loop operation), then drive at a steady speed between 30 and 45 mph for two minutes.

Toyota: The catalytic converter monitor will run after driving the vehicle at 40 to 55 mph for seven minutes, followed by driving at 35 to 45 mph for another seven minutes.

An example of some common enabling criteria to run the catalytic converter monitors drive cycle:

  • Minimum 330 seconds since start-up at 70°F
  • Engine coolant temperature is between 170°F - 230°F
  • Intake air temperature is between 20°F - 180°F
  • Time since entering closed-loop is 30 seconds
  • Inferred rear HO2S sensor temperature of 900°F
  • EGR is between 1% and 12%
  • Part throttle, maximum rate of change is 0.2 volts/0.050 sec
  • Vehicle speed is between 5 and 70 mph
  • Fuel level is greater than 15%
  • Engine RPM 1,000 to 1,600 RPM
  • Engine load 15 to 35%
  • Inferred catalyst temperature 850°F - 1,200°F
  • Number of front HO2S switches is 50

An example of some common enabling criteria to run the catalytic converter monitors drive cycle:

  • RPM range greater than idle
  • Air mass range greater than 5.67 g/sec
  • Purge duty cycle of 0%
  •    Typical Fuel Monitor Malfunction Thresholds:
  • Lean Malfunction: LONGFT greater than 25%, SHRTFT greater than 5%
  • Rich Malfunction: LONGFT less than 25%, SHRTFT less than 10%


The following is a Honda OBDII Drive Cycle Pattern. (Obey all traffic laws while performing drive cycles. Perform acceleration steps only on highways).

COLD START: Begin from Cold Start, and ignition key in OFF position for at least 1 hour. Ensure your Honda’s fuel tank is between 1/4 and 3/4 full and engine coolant temperature must be below 122°F and within 11°F of the ambient air temperature. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

IDLE TIME: Run your Honda’s engine (do not drive) for 2 1/2 minutes with the air conditioner on and rear defroster on. During this period the ECU will be running the Oxygen Sensor Heater self-test, Air Injection System Passive Air test, EVAP Purge "No Flow" test, Misfire Detection.

ACCELERATE: Turn off the air conditioner and rear defroster and begin driving. As soon as possible apply half throttle until 55mph is reached. The ECU will now run self-tests on the Misfire Detection, Fuel Trim, and EVAP Purge Flow.

HOLD STEADY: Now hold your vehicle speed steady at 55mph for three minutes. During this time the Oxygen Sensor O2 response, Air Intrusive (AIS System), EGR Flow, Purge Valve, Misfire Detection, and Fuel Trim diagnostics will be performed.

DECELERATE: During this step you want to slowly let off the accelerator pedal. Do not brake or shift your Honda in order to slow down. It is important to let the vehicle coast along gradually slowing down to 20 mph. The ECU will once again self-test the EGR System, EVAP Purge System and Long Term Fuel Trims.

ACCELERATE: Go ahead and accelerate again at 3/4 throttle until 55-60mph is reached. This will perform the same self tests as during the first acceleration step

HOLD STEADY: Hold steady speed once again. This time at 55mph for five minutes. During this time, in addition to running the self-tests as during the first HOLD STEADY step, the ECU will perform the catalyst monitor diagnostics. If the catalyst (Catalytic Converter) is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst, or in order to Complete the CAT Monitor.

DECELERATE: This will perform the same diagnostics as in the first Deceleration. Remember not to press your Honda’s brake or shift gears during deceleration.

This should complete the drive cycle on your Honda Odyssey. To insure all monitors are complete use a scan tool to view the monitors. You may want to complete the drive cycle 2-3 times.