#93653, "Best way to make a CEL stay off for around 200 miles or so."
My car is past due for inspection and I have a CEL (the bastard code 31) on and cant seem to make it stay off long enough to get it inspected. Last year when I got it inpsected I turned off the light and drove straight to the shop to get it inspected and they said I have to drive 150 miles to completely clear the code from the ECU. Is this true? If so whats the best way to make the code stay off long enough to get it inspected ( I've disconnected the negative terminal, and unplugged the ECU and it wouldnt stay off for more than 30 miles ) I have also tried to replace my gas cap with no results. Any advice ? and for all you smartasses I dont want to hear pay to get it fixed because its 70 dollars (fee to run diagnostics) just to tell me what I already know.
#93654, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 0
The CEL 31 is for the EVAP purge, right?
If so I had the same problem with my car when it was pratically stock. In Massachusetts there is a clause if your ECU is "not ready", I.E. you unplugged the ECU for a few minutes immidately before inspection, they do a smog test. This is how I passed my last inspection (of course back then I had the 8 injector setup and a catalytic converter). If your ECU is ready, there is no smog test at all.
I don't know how it works in your state... I guess it's different.
#93659, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 1
Cel 31 if i recall is for a vacuum (small) leak in the emissions system. you have a leak.
The reason the code comes up because when you start the car the ECU will operate the Leak detection pump within the first 40 seconds (i think its 40secs, migfht only be 20) and when it detects a leak it will throw a code. Chances are you have a bad vacuum line and leaking gas cap. Also if you start your car and leave it run while getting gas.....you will have a code as well; however, you will get the code for large leak.
In my experience the vacuum lines that fail are in the fender well where they are exposed to rain ect. replace all those and try it again. should only cost you less than 10.00. There is a rollover valve on the tank that if it fails can do this as well but I have yet to see that be the cause, even on a boosted car. Mine has been boosted for more than 2 years and i have never had that problem on my 96 or 97 but thats just me.
#93660, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 2 Oct-07-05 03:05 AM by thedawg
Originally posted by Star Turbo Talon Cel 31 if i recall is for a vacuum (small) leak in the emissions system. you have a leak. The reason the code comes up because when you start the car the ECU will operate the Leak detection pump within the first 40 seconds (i think its 40secs, migfht only be 20) and when it detects a leak it will throw a code.
CEL 31 is actually a half dozen or more different possible issues. Pull the actual OBD or DTC code at autozone to be sure.
I just passed the most stringent emissions in the US yesterday (urban socal test only) with a "small evap leak." The leak is from a torn diaphragm on the evap valve between the gastank and spare tire because I used to be boosted. My 99 does not test the evap system when the tank is completely full, so I just reset the ECU, drove it for a day (3 starts, 60 miles) and it passed perfectly with no CEL.
I can guarantee you will fail unless you drive it for at least 30 minutes at varying speeds as the ECU's "fuel monitors" will not be set and the OBD2 smog check tests for that. This is the "150 miles" the smog tech was referring to. There's actually a manual that lists the monitor conditions required before a smogcheck that most smog ref's have on their desk.
*Disclaimer- I have heard on 2GNT that "96-97's *DO* test evap with a full gas tank". Also that "it takes 50 starts since last ECU reset" to run all neccesary diagnostics. Also that "on a 98 if you disconnect and cap off the EVAP vacuum hoses on the throttlebody and intake manifold" it will not throw a code. I cannot verify any of these claims, and I'm skeptical, but there ya go.
For more information, search 2GNT with the following terms: P0441 P0442 P0443 P0455 P0456 P1494 Leak Detection Pump LDP Evap
#101420, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 3
I had the EVAP solenoid code a few years back, i replace it myself but the damn CEL wouldn't shut off, or i'd clear it myself and it'd come back. So the guy at the inspection place told me I'd have to pay 35 to clear it and I told him I'd be back tomorrow
The next day I went back to the place having removed the CEL Bulb hehe. Well he plugged it in again and then proceeded to yell at me (17 years old at the time) and ask me if I thought he was an idiot. So I argued with him for a good ten minutes and convinced him to do the smog/emissions test with the test pipe thing you stick in the muffler... it passed with flying colors... preferably i think the smog test is better only because its measuring whats actually happening, not looking at any crazy problems or codes with our ECUs.
#101427, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 4
They're called drive cycles. I have all of them somewhere written down, and some are ridiculously complex. Any decent scantool machine (MODIS, genisys) will know if the ECU has been reset recently.
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96 Black ESi 91 Red TSI AWD (RIP) 02 WRX
"turnin wrenches for nine hours in the pouring rain, just to get the beast up and running again"
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#101491, "RE: Best way to make a CEL stay off for around 200 miles or so." In response to Reply # 7
In case you haven't been paying attention, by clearing your codes prior to inspection, you clear the rest of the monitors making it in a "not ready" state.
I would try Dan's idea of having the gas tank full as possible, long enough to establish the monitors without having the CEL come up. I will need to try that the next time I go in for a SoCal SMOG.
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