Disappearing CEL

[RaceOn]

Hi Guys,

My '99 Rodeo 3.2L is giving me fits. I get a CEL and then when I go to have it read, it goes away and the reader lists no code. It's done this four times with three different readers. When the light is on, as soon as you plug in the reader the reader lists no code and you start the engine and the light is off. It will return in about three days.

The last time I had a code register it was related to the gas cap and/or EGR, I think it was a P0440 or a P0401. I replaced the gas cap, cleaned the EGR and the tube under the intake manifold. That lasted about three weeks and then this started happening. I can't really say if the two are related because I can't pull the code that triggers the CEL.

Does anyone have any ideas?

Thanks,
Pat

[old_master]

You need to access the history file, the DTC will be there. The ONLY way to access and clear the history file is with a scan tool, not a code reader. Disconnecting the battery won't even clear it. El cheapo scan tools, (entry level) start around $2,000.

[RaceOn]

Originally Posted by old_master

You need to access the history file, the DTC will be there. The ONLY way to access and clear the history file is with a scan tool, not a code reader. Disconnecting the battery won't even clear it. El cheapo scan tools, (entry level) start around $2,000.

Hmmmm, $2k to clear a code? Wow, I guess I will just have to live with it. Thanks for the quick response.

Pat

[old_master]

It's not a matter of clearing it, you need to find out what the problem is and correct it. Shops will charge anywhere from $30 $80 to retrieve DTC's. Once you have it, then you can troubleshoot it. Beats spending big money on a scan tool, plus you're getting the knowledge of the technician checking it, small price to pay

[Cat Fuzz]

I had a car once that had a CEL on permanently but never could read a code. Turned out there was a wiring problem somewhere (short or something) making the light come on but there was no issue at all with the ECM. As far as the ECM was concerned, there were no problems and the ECM was reporting that the CEL was off. A high end scan tool will be able to get more information from the ECM and perhaps give better clues than simply reading the codes. Taking it to a shop that is equipped with such a scan tool may be your only option.

[RaceOn]

Thanks for the help guys. I have a friend that has a high end scanner and he is going to come over this afternoon and see if we can figure this thing out. I'll let you know what we find.

Thanks,
Pat

[RaceOn]

OK, I had a friend use two different scanners (Snap-On and Matco) to read what was going on. The CEL was on, so he plugged in, turned the key and the light went out. The codes that were stored were the gas cap and the EGR system. On the oft chance that the previously replaced gas cap was a problem, I went to the local Honda store and purchased an Isuzu replacement cap. I have driven the car about 220 miles and so far the light has stayed off. I guess time will tell how this fix works out. I guess at 147k miles the old girl is showing her age.

Pat

[old_master]

Thanks for posting back with the "fix".