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  1. #1
    morsetaper2 is online now Titanium
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    Default OT: Repair Made, Check Engine Light Off, How Long to Take Emissions Test?

    Vehicle: 2001 Ford Ranger PU truck

    Check Engine Light (CEL) has been on for some time. I made repairs & reset the CEL by battery disconnection yesterday (Sat 10/23). The CEL has stayed off over two cold start driving cycles. 2X previous when the code was cleared (no repair made), the CEL would come right back on like 15 minutes later.

    I have a MD state emissions test deadline coming up on Wed (10/27). How long (or how many cold start cycles) will I have to go through before they will accept my vehicle for an emissions test?

    Background:

    I have had this CEL on for code P0401 (insufficient EGR flow) for some time. Yesterday I removed the entire EGR system (diaphragm, tubes, hoses, & throttle plate assy). Non of it was clogged but I ran a pc of motorcycle clutch cable w/ ends frayed chucked in my cordless drill into all the tubes/passageways to be certain they were all clear.

    And I replaced the DPFE (Differential Pressure Feedback Sensor) as word on the Ford Ranger truck forums is this $50 sensor is the culprit nearly all the time. I have replaced this sensor 2X previous for the same code and it had solved the problem both times.

  2. #2
    PixMan's Avatar
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    Drive it for at least 75 and up to about 150 miles. If it's not back on by then, you're OK. The problem with many code readers is that they only read codes. When the system hasn't reset and is still in a "not ready" state, you get no codes but also no reading @ the inspection station. Your vehicle will fail if it reads "not ready" to their system.

    I have a BMW that's throwing a "below threshold limit" code for the catalytic converters. After replacing all four O sensors, I still get the codes. I reset them, and it takes anywhere for 50 to 100 miles and the light comes right back on. Guess I'm going to have to start saving for the two $850 (each) cats, and that's a "refurbished" price. Over $1500 each new. Ouch. Consider yourself lucky.

  3. #3
    JDRoberts is offline Plastic
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    You need to have all but 1 of the "monitors" set to ready for it to pass.

    all is better,but 1 is allowed "not ready" status,doesnt matter which one.

    here's a common "drive cycle"...

    To perform an OBDII Driving cycle do the following:

    1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50C (122F) and within 6C (11F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
    2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
    3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
    4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
    5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
    6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
    7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
    8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
    usually the most difficult to set are catalyst and evap.

    just an FYI:if a repair is made specifically for emission testing,don't disconnect the battery.

    just drive the vehicle normally.
    as soon as the monitor that tests that particular system runs,it will bump the code to "history" status and set the monitor to ready without changing the status of the other monitors.usually takes alot less time.
    for emission testing,any code that does not turn on the "check engine" light,doesn't matter.
    only active codes that set the light,matter.

  4. #4
    cvairwerks is offline Aluminum
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    We have a 96 Plymouth Grand Voyager that had a similar problem. Even after 250 miles of hard freeway driving, and probably 30 starts, it wouldn't reset the codes. I'd run by the inspection place every couple of days and let them check it with their computer, all to no avail. We finally ended up disconnecting the battery a half dozen times and forcing an engine computer reset several times and then it suddenly cleared itself. Aparently, for some reason, the ECM stubbornly wouldn't release one code. All that trouble for a supposedly bad sensor.....that turned out to not be bad after all.

  5. #5
    Gary E is offline Diamond
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    Quote Originally Posted by JDRoberts View Post
    To perform an OBDII Driving cycle do the following:..................
    Do these requirements differ by STATE?... and maybe each car??

    Because when they check my 1992 Buick Roadmaster in Texas, the ONLY connection to the car is a wire clamped around one sparkplug wire to sense RPM and a probe stuck in the tail pipe.

    They also NEVER go over 30 or 35 MPH... with the rear wheels sitting on the rollers.

    I also cant imagine your cold start requirement of that low of coolant temp... hell, ambiant around here when I have that done is close to 98F and they dont let it sit long in the parking lot to cool off from the normal operating temp.

  6. #6
    Fasto's Avatar
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    Quote Originally Posted by Gary E View Post
    Because when they check my 1992 Buick Roadmaster in Texas, the ONLY connection to the car is a wire clamped around one sparkplug wire to sense RPM and a probe stuck in the tail pipe.
    A 1992 car won't have ODB2. ODB2 started on some '94 models and was required on all '96 models. Years might be a bit off, memory isn't so good anymore.

    Here in MA, if your car is not ODB2 it's automatically emissions exempt. There just aren't too many cars here older than '94 any more. We used to have the roller dyno tests - no longer, they just plug in and ask the car if it's OK.

    Luckily, my 1993 and 1978 cars aren't ODB2...

  7. #7
    Butch Lambert is offline Stainless
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    GaryE,
    Fausto is correct, you have an OBD1 system and not the OBD11. They are checked in Texas 2 different ways.
    Butch

  8. #8
    PixMan's Avatar
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    In MA they ditched the sniffers a few years ago because those were too easy to circumvent by just running the test with some other compliant car. With OBDII, it registers the computer of the car to the diagnostic machine. In The Commonwealth they also use an internet video connection to monitor the tests. Big brother doesn't want anyone cheating!

  9. #9
    W. Johnson's Avatar
    W. Johnson is offline Cast Iron
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    How long (or how many cold start cycles) will I have to go through before they will accept my vehicle for an emissions test?
    My boss had a late '90s Lincoln that the CEL was on for about 6 months. Car ran fine and he didn't want to pay to fix it. I have an OBD2 code reader that will wipe the codes and turn off the CEL. It would come back on after it was driven about 40 miles.

    I was told that with OBD2, if the CEL is not on, it will pass. There is no tailpipe sniffing on OBD2 in MD.

    One morning I cleared the codes and took it to the testing station. It was plugged in to their computer about 1/2 hour after I cleared the codes. Passed the test with no problems. He drove it almost 2 more years with the CEL on before he sold it.

    Wayne

  10. #10
    jdj
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    Quote Originally Posted by JDRoberts View Post
    You need to have all but 1 of the "monitors" set to ready for it to pass.

    all is better,but 1 is allowed "not ready" status,doesnt matter which one.

    here's a common "drive cycle"...



    usually the most difficult to set are catalyst and evap.

    just an FYI:if a repair is made specifically for emission testing,don't disconnect the battery.

    just drive the vehicle normally.
    as soon as the monitor that tests that particular system runs,it will bump the code to "history" status and set the monitor to ready without changing the status of the other monitors.usually takes alot less time.
    for emission testing,any code that does not turn on the "check engine" light,doesn't matter.
    only active codes that set the light,matter.

    You forgot to mention that you have to make a certain face throughout this procedure! (smiley face)

    Jeff

  11. #11
    Axle's Avatar
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    An additional ford drive cycle procedure;
    Ford Motor Company Driving Cycle

    If you have access to a more advanced scan tool you can check readiness codes yourself, and run the related drive routine to set it. Also note, that some states allow 1 or 2 unset readiness codes.

    Alex.

  12. #12
    JBishop is offline Hot Rolled
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    A lot of the less expensive scan tools have readiness monitors on them now. Mine has 3 leds green, yellow, and red, and I have found it can sometimes take quite a while to pass all the monitors, evap seems to be the longest. My own truck took about 3 weeks of driving, around town, highway, hot, cold, you name it, before it was ready. Didn't evem know it had this feature till I went to get a sticker, no CEL on, and they gave me a reject sticker cause it's "not ready". Perhaps you know someone into cars who has one? HTH Jim.

  13. #13
    morsetaper2 is online now Titanium
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    OK, after 3 days, 3 or 4 cold starts, & 127 miles of driving I drove in and passed the MD emissions inspection.

    Thanks for all of your input.

    Mark

  14. #14
    Axle's Avatar
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    That is something that has always irked me about emmisions tests: All the extra driving, parts replacement, out of schedule oil & filter changes that you need to do in the name of being environmentally friendly.

    Alex.

  15. #15
    JDRoberts is offline Plastic
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    Default Re: OT: Repair Made, Check Engine Light Off, How Long to Take Emissions Test?

    Quote Originally Posted by Axle View Post
    An additional ford drive cycle procedure;
    Ford Motor Company Driving Cycle

    If you have access to a more advanced scan tool you can check readiness codes yourself, and run the related drive routine to set it. Also note, that some states allow 1 or 2 unset readiness codes.

    Alex.
    It depends on the year of the vehicle.96-2000 are allowed 2 "not ready" monitors,01 and newer are allowed only 1.

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