Hold at a steady state speed of 55 mph for 3 minutes. The computer will now be testing the EGR system, air injection pump, O2 sensors and canister purge. Decelerate to 20 mph without braking or depressing the clutch. Once again the computer system will check EGR and purge functions. Accelerate back to 55 to 60 mph at half throttle.
Hold at a steady speed of 55 to 60 mph for 5 minutes. Decelerate to a stop without braking or depressing clutch. We recommend completing this drive cycle at least twice in order to insure all required parameters have been met. Thanks Shaun! A few questions. Secondly, for step 3, whats the delay between idling and then getting up to 55?
And last question, I was considering disconnecting battery to start all from scratch and doing 2 complete drive cycles, but the smog guy advised against that bc it would reset everything. Any suggestions? Industry knowledge. Last updated Sep 05, Make Sure the Engine Light is Off The first and foremost step is to check whether the engine light is off. Check if your Vehicle has a Coolant Temperature The drive cycle starts with a cold start.
Let the Engine be Idle for 2 Minutes The next step is to start the engine and keep it idle for two and half minutes, keeping rear defroster and AC on. Stop the Vehicle Now, make your vehicle slow down and allow it to sit idle for 2 minutes. The EVAP monitor should be complete. The Heated Exhaust Gas Oxygen sensor monitor makes sure the oxygen sensors are functioning properly and are operating within their normal range.
The monitor runs after the engine has reached normal operating temperature, and the vehicle is cruising at a specified speed for a specified length of time. This monitor will not run if there are any faults in the oxygen sensor heater circuit, if there are any pending oxygen sensor codes, or the engine coolant or vehicle speed sensors are not functioning normally.
Ford: The HEGO monitor should run when the engine has reached normal operating temperature, the inlet air temperature is between 40 and degrees F, and the vehicle is cruising at a steady 40 mph for four minutes. This checks the O2 heater circuit. This will complete the second half of the HEGO 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 HEGO monitor should run after idling the engine for nine minutes, then driving at a steady 25 mph for two minutes. The Catalyst Efficiency Monitor verifies the catalytic converter is operating at high enough efficiency to keep exhaust emissions within acceptable limits.
The monitor compares the signals from the upstream and downstream oxygen sensors to monitor the operation of the catalytic converter. As a rule, if converter conversion efficiency drops below 80 percent for any pollutant carbon monoxide, hydrocarbons or oxides of nitrogen , the vehicle may be polluting, causing a code to set. The catalyst monitor may set a code if converter efficiency is less than 90 percent.
Converters typically fail one of two ways: they get too hot, melt and plug up, or the catalyst becomes contaminated and useless. Diagnosing a plugged converter is fairly easy, but diagnosing converter efficiency requires tapping into the OBD II system with a scan tool to check for codes and to compare the upstream and downstream O2 sensor readings.
Plugging is usually caused by unburned fuel entering the exhaust system. A fouled spark plug, bad plug wire or a bad coil on a DIS system causes ignition misfire that overloads the converter with fuel.
A leaky exhaust valve can do the same thing, allowing unburned fuel to pass right through the engine without being ignited. Most converters are designed to operate at a temperature of to degrees F. When the exhaust temperature hits about degrees, the catalyst starts to trigger the chemical reactions that break down the pollutants.
This releases heat, causing the converter to light off. The temperature shoots up and things really start cooking. But if there's too much HC in the exhaust, the converter may get too hot.
At temperatures above degrees F, the catalyst can begin to melt and even the ceramic or metallic honeycomb that supports it. We've seen converters that have been melted into a solid glob, creating a complete blockage of the exhaust.
We've seen others that still pass some gas, but create enough restriction that backpressure chokes the engine and causes a noticeable loss of power and fuel economy. If a vehicle lacks high speed power, is struggling to breathe or stalls after starting, the converter may be plugged.
To confirm the diagnosis, you can hook up a vacuum gauge to the intake manifold and note the vacuum reading. If intake vacuum is low and continues to drop while the engine is idling, exhaust backpressure is building up and choking the engine. You can also check exhaust backpressure ahead of the converter by connecting a pressure gauge to the EGR exhaust port, an O2 sensor port, or an exhaust manifold air line connection. More than 1. Diagnosing converter efficiency to see if the converter is still doing its job can be done a couple of ways.
There should be a significant drop in the readings if the converter is working.
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