Strange CEL

khanselman · #1 06-04-2008, 09:50 AM

Before I start my story - 2002 Civic DX / ~150k miles / Auto / AEM SRI / Magnaflow catback

Last weekend I was driving home from my parents house and about a mile down the road I pushed on the gas peddle like normal and the car seemed to bog, didn't want to shift, and was acting strange. I've had it once where it wouldn't shift past second and I just pulled over, shut it off and started back up again and it worked, so I tried that... and it seemed to work. About a mile down the road it started up again and my CEL came on. I was low on gas at the time (CEL came on at same time as Low Gas light), so I pulled into the next gas station and put $25 in and started the car back up. Pulled away and about 100yrds down the road the CEL went off and car drove fine.

I drove the car all week with no problems - to and from work (12mi one way) and grocery shopping, etc. Everything seemed to be running fine, so I figured the CEL and bogging engine had something to do with low fuel level. Today I got in and started to work and it started happening again - bogging, not shifting at the right points, etc. so I looked and both Gas Light and CEL were on again. I drove to the nearest AutoZone and had them read the CEL and it was P0122 - TPS - "The PCM has determined that the input from the throttle position sensor is lower than expected for the current engine operating conditions."

I searched on here for TPS and read that it's a $600 replacement from Honda because they replace the whole TB [:@] - or $80 for a new TPS that I could install myself on my current TB. I checked the engine bay and I didn't see anything wrong with the wires or plug, and when I get my hand on a volt meter I will check the middle pin (read it should be between .45 - .50 for idle and 4.45+ for WOT) to make sure everything there is working correctly.

But this leads me to my question.. It seems to only be happening when I am low on gas. I will fill up on my way home today to verify - but like I said it has happened twice when I get to about 1gal left in the tank and stopped when I filled up.

RonJ · #2 06-04-2008, 11:48 AM

I will speculate on this unusual problem. In a nutshell, I think you have a faulty TPS or TPS circuit that is causing all the problems. I think that the Low Fuel indicator gets triggered by the engine bogging due to the TPS problem and that the resulting power fluctuation from the alternator results in lighting of the Low Fuel indicator, which is almost ready to do so anyway.

khanselman · #3 06-04-2008, 12:49 PM

Well, the Low Fuel light comes on because I DO in fact have low fuel... just seems like the only time this happens is when I do have low fuel.. that's what my question was - why would this happen if I had low fuel?

RonJ · #4 06-04-2008, 01:02 PM

I think the engine bogging triggers the Low Fuel light to turn ON a little sooner than it might otherwise. I mean no disrespect, but having the TPS problem on two separate occasions when the fuel level happened to be low does not necessarily make a pattern.

Nonetheless, if you feel that a low fuel level has a causal role in the problem, then you might consider letting the fuel level get to about 1 gallon and then drain the tank to see if debris or water has concentrated in this remaining fuel. You might also consider doing a fuel treatment.


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