The Dreaded CEL & Code P0410
09-24-2005, 12:15 PM
#16
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Originally Posted by Lorenfb
When a DTC (diagnostic trouble code) is reset via a scanner, the sensors are NOT affected.
Reseting the DTC also resets the readiness states which indicate the self-test state
of the emission system. Once this occurs, the vehicle must be driven to again SET
the readiness states.
Reseting the DTC also resets the readiness states which indicate the self-test state
of the emission system. Once this occurs, the vehicle must be driven to again SET
the readiness states.
09-24-2005, 12:18 PM
#17
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Originally Posted by Lorenfb
"When you reset, at least with my scanner, all you do is turn off the sensors (don't know if this is the right word) - they do not read until reset. These sensors are reset through normal driving over time, or by going through the readiness reset routing as documented on Rennlist."
When a DTC (diagnostic trouble code) is reset via a scanner, the sensors are NOT affected.
Reseting the DTC also resets the readiness states which indicate the self-test state
of the emission system. Once this occurs, the vehicle must be driven to again SET
the readiness states.
To state that driving at high RPMs will reduce the likelihood of a SAI CEL is misleading.
If the engine has a valve guide wear problem, this will only accelerate the SAI problem.
For more SAI info, check here ( www.systemsc.com/pictures.htm ).
For OBDII info, check here ( www.systemsc.com/codes.htm ).
When a DTC (diagnostic trouble code) is reset via a scanner, the sensors are NOT affected.
Reseting the DTC also resets the readiness states which indicate the self-test state
of the emission system. Once this occurs, the vehicle must be driven to again SET
the readiness states.
To state that driving at high RPMs will reduce the likelihood of a SAI CEL is misleading.
If the engine has a valve guide wear problem, this will only accelerate the SAI problem.
For more SAI info, check here ( www.systemsc.com/pictures.htm ).
For OBDII info, check here ( www.systemsc.com/codes.htm ).
Yes - I think we're mixing our terminology a little. When clearing DTCs, what gets reset are the "monitors". The monitors maintain a "has run" and "has not run" state. Some monitors are continuous (e.g. misfires, fuel) while other require the "trip" or OBD cycle to be completed and get set to "has run". It's these cycles that require the exacting reset procedure.
-Eric
09-24-2005, 12:35 PM
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Originally Posted by Father of 3
That's what I was trying to say but couldn't describe it accurately. If the readiness states are not ready, doesn't that mean the system will be unable to detect the fault, at least until the readiness states are reset? That was my point.
-Eric
09-24-2005, 12:38 PM
#19
"If the readiness states are not ready, doesn't that mean the system will be unable to detect the fault, at least until the readiness states are reset? That was my point."
The DME continuously monitors the sensors to determine how the fuel & ignition outputs
should operate (basically). If the DME determines a bad sensor, e.g. out of range, it will set a DTC.
This is the "lowest level" of the overall ODBII system. The next higher level, basically,
is the readiness states.These states may or may not complete (SET) based on the
DTC fault. So, again basically, the DTCs and the readiness are somewhat independent
functions.
Bottom line:
The DTCs indicate the functionality of the DME operation.
The readiness states monitor the functionality of the emission system, i.e. the O2 sensors, the CAT,
& the SAI. This is what defines the difference between ODBI & OBDII.
The DME continuously monitors the sensors to determine how the fuel & ignition outputs
should operate (basically). If the DME determines a bad sensor, e.g. out of range, it will set a DTC.
This is the "lowest level" of the overall ODBII system. The next higher level, basically,
is the readiness states.These states may or may not complete (SET) based on the
DTC fault. So, again basically, the DTCs and the readiness are somewhat independent
functions.
Bottom line:
The DTCs indicate the functionality of the DME operation.
The readiness states monitor the functionality of the emission system, i.e. the O2 sensors, the CAT,
& the SAI. This is what defines the difference between ODBI & OBDII.
09-24-2005, 02:08 PM
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Originally Posted by Lorenfb
The readiness states monitor the functionality of the emission system, i.e. the O2 sensors, the CAT, & the SAI.
I think we are saying the same thing though my point is being muddled by my butchery of the terminology and a mix of apples and oranges.
09-24-2005, 04:54 PM
#22
"If you trip an SAI code, reset via a Kragen scanner thereby making the readiness states not ready, then procede to drive the car to the ready state, wouldn't the SAI code just come back on?"
Yes, that's correct. A SAI DTC sets because of the readiness state/monitor failure.
So, when using a scanner, the vehicle would have a fault code (DTC) and that part
of the OBDII monitoring system, i.e. the readiness state, would show an incompletion
for SAI. With this incompletion, checked at the start of an emissions test, the emission
test would be aborted.
Note: The SAI air passages may not be the real cause of the SAI readiness incompletion.
As an example, if the O2 sensors fail to reach the OBDII check point value, a SAI incompletion
will result.
Yes, that's correct. A SAI DTC sets because of the readiness state/monitor failure.
So, when using a scanner, the vehicle would have a fault code (DTC) and that part
of the OBDII monitoring system, i.e. the readiness state, would show an incompletion
for SAI. With this incompletion, checked at the start of an emissions test, the emission
test would be aborted.
Note: The SAI air passages may not be the real cause of the SAI readiness incompletion.
As an example, if the O2 sensors fail to reach the OBDII check point value, a SAI incompletion
will result.
09-24-2005, 07:10 PM
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As another example of Loren's note above, I had the SAI code show up. Upon further monitoring, I found intermittent O2 sensor faults. The whole mess was resolved when I replaced a faulty MAF sensor. When this first started, the shop that first discovered the codes saw the SAI failure code and several of the techs started laughing and telling me how screwed i was (they know me) and asking when they should start the disassembly of the engine. There refrain "EVERY '97 993 has this problem...."
