Code Scanning
Elder User
Joined: Sep 2004
Posts: 941
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Run the engine off test first. If you are getting "hard codes" (the ones before the separator pulse), these are the easiest to deal with, and often are fairly critical to the engine operation. You will get the memory codes after the separator pulse; write them down but worry about dealing with them yet.
Personally, I would not bother running a KOER test if I was getting hard codes in the KOEO test, unless I could dismiss the KOEO codes as something I didn't care about for right now (like transmission codes).
Once you get the KOEO test to pass without hard fault codes, move on to the KOER test. If it gets codes, deal with them next.
Once both the KOEO and KOER tests consistently pass, then it is time to drive the truck around for a while. Stop the truck and run another KOEO test. See if the computer posted any continuous memory codes, and deal with them now.
Personally, I would not bother running a KOER test if I was getting hard codes in the KOEO test, unless I could dismiss the KOEO codes as something I didn't care about for right now (like transmission codes).
Once you get the KOEO test to pass without hard fault codes, move on to the KOER test. If it gets codes, deal with them next.
Once both the KOEO and KOER tests consistently pass, then it is time to drive the truck around for a while. Stop the truck and run another KOEO test. See if the computer posted any continuous memory codes, and deal with them now.
Senior User
Joined: Nov 2003
Posts: 172
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Will the computer register any codes without the Check Engine light coming on? I am wondering if there is any advantage to checking for codes as a preventive measure if the truck is running fine, and no Check Engine light on, just to catch any potential developing problem early, or is this a waste of time? Also, if I do decide to check (depending on what advice you give), is there anything I can screw up by checking--I am not very mechanically inclined.
Thanks,
Frank.
Thanks,
Frank.
Elder User
Joined: Mar 2004
Posts: 537
Likes: 2
From: Alabama
I would say it would not hurt you to read codes periodically even without a CEL lit. I'm getting a couple now with no CEL lit that could indicate some type of problem that needs to be looked at. What do you plan on reading the codes with? Reader, paper clip, blinker?? Don't really think you could screw much up. Just read up on how to read the codes first and then follow each step and pay attention. Mine are showing up on the KOER test, BTW.
guzzler96
guzzler96
Last edited by guzzler96; Nov 26, 2004 at 08:12 PM. Reason: sp
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Elder User
Joined: Sep 2004
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The EEC-IV routinely posts codes without a CEL. In fact, it is more common than not that the CEL will not stay on. The CEL is only lit when a condition is happening "right now". So something that happens only at certain RPMs and moderate loads will light the CEL only at those times. The light will go out when conditions change.
OBD-II vehicles (1996 and beyond) work differently. They have the government-mandated concept of a "drive cycle". If a condition has been indicated, and maintained through a "drive cycle", they will set the CEL. The CEL will then stay on until the codes are reset (with a scanner, or by pulling off the battery cable), even if the problem goes away. Code 420, and its bretheren, "Catalytic converter efficiency below threshold" is the most infamous family of these.
Be careful when installing the "get the codes" jumper. Shorting STI or SIGRTN to battery voltage can damage the computer. But you can ground either with impunity.
OBD-II vehicles (1996 and beyond) work differently. They have the government-mandated concept of a "drive cycle". If a condition has been indicated, and maintained through a "drive cycle", they will set the CEL. The CEL will then stay on until the codes are reset (with a scanner, or by pulling off the battery cable), even if the problem goes away. Code 420, and its bretheren, "Catalytic converter efficiency below threshold" is the most infamous family of these.
Be careful when installing the "get the codes" jumper. Shorting STI or SIGRTN to battery voltage can damage the computer. But you can ground either with impunity.
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