Team ZR-1

Type A diagnostic trouble codes are the most serious and will trigger the MIL lamp with only one occurrence. When a Type A code is set, the OBDII system also stores a history code, failure record and freeze frame data to help you diagnose the problem.

Type B codes are less serious emission problems and must occur at least once on two consecutive trips before the MIL lamp will come on. If a fault occurs on one trip but doesn’t happen again on the next trip, the code won’t "mature" and the light will remain off. When the conditions are met to turn on the MIL lamp, a history code, failure record and freeze frame data are stored the same as with Type A codes.

A drive cycle or trip, by the way, is not just an ignition cycle, but a warm-up cycle. It is defined as starting the engine and driving the vehicle long enough to raise the coolant temperature at least 40 degrees F (if the startup temperature is less than 160 degrees F).

Once a Type A or B code has been set, the MIL will come on and remain on until the component that failed passes a self-test on three consecutive trips and if the fault involved something like a P0300 random misfire or a fuel balance problem, the light won’t go out until the system passes a self-test under similar operating conditions (within 375 rpm and 10% of load) that originally caused it to fail.
That’s why the MIL lamp won’t go out until the emissions problem has been repaired. Clearing the codes with a scan tool or disconnecting the powertrain control module’s power supply won’t prevent the lamp from coming back on if the problem hasn’t been fixed. It may take one or more driving cycles to reset the code, but sooner or later the MIL lamp will go back on if the problem is still there.

Likewise, the MIL won’t necessarily go on if you intentionally disconnect a sensor. It depends on the priority ranking of the sensor (how it affects emissions), and how many driving cycles it takes for the OBDII diagnostics to pick up the fault and set a code.

As for Type C and D codes, these are non-emissions related. Type C codes can cause the MIL lamp to come on (or illuminate another warning lamp), but Type D codes do not cause the MIL lamp to come on.

So Class A is assured to trip ASAP, B requires at least the error occuring twice at same conditions and C and D more laxed.

If smog station just uses a scanner as long as no SMOG DTCs exist and IMs are in a complete state then you pass, if you switched a class A to C, that would sneak you past tests, so higher the class the less chances of it being seen.

Again, all IM smog test will do is look for complete state of all IM 240 tests and no class A or B (smog related) DTCs.

<small>[ August 15, 2002, 04:42 PM: Message edited by: Team ZR-1 ]</small>

RPM WS6

iTrader: (3)

I know I have read TeamZR1 post before that as long as you leave emission tests functional, you will pass the scan if you don’t have any MIL triggering emission codes. I also know that I have read that you can turn the MIL light “off” but that you’ll be ok as long as you leave the test on. (please correct me if any of this is wrong) But here is a question. Does it matter if I set the DTC to be a Type C = no light or a Type X = off?? Is one better than the other? Will it matter for emissions scans which one I use? Will one of them not pass?

Basically, if I set the test to “on” and the MIL to a “Type X” will this pass the scan? Or do I need to do a test “on” and MIL “Type C”?

Thanks in advance <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ August 15, 2002, 12:39 PM: Message edited by: RPM WS6 ]</small>