: Catera OBDII Questions



investor74
11-01-06, 10:36 PM
Hi

I bought an OBDII reader to see why I get the check engine light on and off every couple of weeks for about the last two years. The car is running smoothly, good MPG. I previously associated the CEL with a loose gas cap, and it went off after a few start cycles.

Question #1 - During the "read" cycle, I get a noise from the engine compartment, lasting about 3 seconds. It sounds like a relay turning on and off or something, like a ratchet sound. What is this sound? I thought the "read" cycle is simply a passive "read" of codes already in the on-board computer. At first, I thought the sound was signal interference that I was hearing on the radio, but I turned the sound all the way down and I still hear it.

Question #2 - I read a P0134 (O2 sensor issue). The code was there when the check engine light was on, and was there when it the CEL turned itself off. What does it mean when the code is there, but not the CEL? Incidently, the Cat passed the emissions impection last week. I waited until the CEL turned itself off, but I guess the P0134 did not show up on the State's reader.

Question #3 - The manual that comes with the tester has all kinds of warnings about erasing the codes - you will lose valuable information that can be used for diagnostics of the problem, etc. Anyway, I erased the code tonight just to see if it would stay away. Did I make a mistake in doing this?

Thanks,

Barry

Warez
11-01-06, 10:52 PM
Q1: Try localizing the noise, is it coming fron the under hood fuse panel or somewhere else?

Q2: The PCM has a code history where old codes are kept even after the issue is resolved. You can clear the history depending on which scantool you're using.

Q3: Is this referring to the history and or current codes? If the latter I don't see a problem with clearing the code beacuse it will just come up again if it continues to be an issue.

investor74
11-02-06, 11:42 AM
Q1: Try localizing the noise, is it coming fron the under hood fuse panel or somewhere else?

Q2: The PCM has a code history where old codes are kept even after the issue is resolved. You can clear the history depending on which scantool you're using.

Q3: Is this referring to the history and or current codes? If the latter I don't see a problem with clearing the code beacuse it will just come up again if it continues to be an issue.


Here is what the manual says:


CAUTION: Erasing the Diagnostic trouble Codes allows the
Auto scanner to delete not only the codes from the vehicle’s
on-board computer, but also “Freeze Frame” data and
manufacturer specific enhanced data. Further, the I/M
Readiness Monitor Status for all vehicle Monitors is reset to
Not RUN or Not COMPLETE status. Do not erase the codes
before the system has been checked.

I tried resisting erasing the code for about three weeks owning the OBDII reader, and finally I caved in. I just wanted to see if this mysterious code will stay away.

Thanks,

Barry

Warez
11-02-06, 05:06 PM
What kind of scanner are you using? I doub't that any codes are actually permanently erasable from the PCM's firware or that your scanner has and write capability unless it's a Tech 2.