PDA

View Full Version : CEL... there it is... and there it isn't!!!



Ghosty
04-27-2008, 05:30 AM
Today, two bad things happened.

One, my odo hit 151k.

Two, my CEL light came on for about 5 seconds. And then vanished.

One thing I know for certain is the electrical in my car isn't that great. Sometimes the lights behind the temp control knobs don't work, or are partially on. Another time, the lights behind the speed cluster didn't come on... at night.

What I'm wondering is if it's a legitimate issue or just a short-term electrical screwup. I've noticed no other symptoms, except perhaps a more pronounced oily-smoky smell under the hood... but that could have been an over-reactive imagination.

Last time I checked the dipstick, it was half way between the "full" and "fill," and this was about 2.5k miles since the last oil change.

Any clues? Ideas about what to look for?

CriScO
04-27-2008, 06:24 AM
151k? Amature! The coupe's at 220k! :) I'm sure that isn't the highest here, either...

Okay, I'll get on topic now. The lights in the heater control unit go all the time, they loose the connection in the printed circuit board that powers the LEDs. That's the issue with the push button unit anyway, it may be different with the knob type.

The dash lights are on the same circuit as the taillights. Have you ever noticed anything happen when you hit the brakes or turn on the blinker? Dash lights dimming, etc.? If so you could have a bad ground connection in that circuit, and on celi's the taillight ground is usually what goes first.

As for the CEL, was it at night? If the above condition is present it can make the power drop below 12v when all accessories are on at idle, and that would've tripped the CEL.

That's what I'd guess.

Ghosty
04-27-2008, 07:33 AM
151k? Amature! The coupe's at 220k! :) I'm sure that isn't the highest here, either...

haha... But it's my baby!!!



Okay, I'll get on topic now. The lights in the heater control unit go all the time, they loose the connection in the printed circuit board that powers the LEDs. That's the issue with the push button unit anyway, it may be different with the knob type.

The dash lights are on the same circuit as the taillights. Have you ever noticed anything happen when you hit the brakes or turn on the blinker? Dash lights dimming, etc.? If so you could have a bad ground connection in that circuit, and on celi's the taillight ground is usually what goes first.


The 5th gen climate control is a knob-type for temperature, and buttons for selecting which vents to use, a/c, vent and defrost. The LED for the vent buttons went a LONG time ago. Now it's the back lighting for that whole display that has the issues.

I do notice that the lights get dimmer at stops. Funny story about that-- one time it kept getting dimmer and dimmmer, and I had no clue why. Eventually the battery was almost gone. Then my dad asked "did you turn your defrost off when you were done using it???" Sure enough... defrost had been on for a long-ass time and was taxing the electrical system.

But to get to the point -- I do slightly notice similar symptoms to that time. Slightly dimming lights at stop. Get on the gas to go, and it's back to normal. I always figured it would be an alternator issue, but if what you say is true, it seems very plausible in my case. It's not tremendously dimmer, but I do notice it.



As for the CEL, was it at night? If the above condition is present it can make the power drop below 12v when all accessories are on at idle, and that would've tripped the CEL.

That's what I'd guess.

It was at night, lights on. No fan was going, no a/c either. I was cruising at about 2.3k RPM. I had no idea a voltage drop would trigger a CEL... but that would explain it.

CriScO
04-27-2008, 09:18 AM
As I understand that's one of the quirks of the Celica electical system, the BATT light is linked with the CEL. If the BATT light comes on it automatically trips the CEL.

I've been reading through the service articles a lot lately, that stood out in my mind because I'd always wondered why both lights came on every time I lost an alternator in either car.

My coupe has some really bad grounding problems in that light circuit that I've yet to get around to fixing. If I'm at a light waiting to turn at night (lights, brake lights, and turn signal on), my voltage will drop to just under 13v when the blinker is lit. If it's storming and my wipers are on I've seen it go down to 12. I've put in an aftermarket voltmeter in case you're wondering how I got the values.

So it seems feasable to me that it could suck the voltage under twelve given the right conditions. The defrost draining it like that points more to alternator issues, though, imo.

85gtsblackman
04-27-2008, 11:56 AM
if the battery and brake light are on that means the alt crapped out

CriScO
04-27-2008, 12:55 PM
^ D'oh! :)

He's totally right, that's the light I was thinking of. Shit. Sorry.

I need to look over that section again... I'm taking the ASE Parts Specialist test in two weeks, I can't be messing up like that!

Gary
04-27-2008, 02:54 PM
CEL will show up when the ECU detects any malfunction.
Some of them only show up only fraction of time and will disappear.
Some error codes are stored in the memory even after CEL is disappeared.
Try pulling the code.

Newbster
04-27-2008, 06:35 PM
Where would the grounds be for the tail lights? Because on the tail lights sometimes one of the "bars" of red dont turn on when I hit the brakes, but sometimes they do.

Ghosty
04-27-2008, 09:25 PM
It happened again just this morning... driving on the same stretch of road, no less! It's like there's some sort of CEL-tripping spirit out here trying to screw with celicas!!!

This time, though, there were no lights on. But I notice that on this stretch of road, I'm clipping along somewhere between 40 and 45mph, and at a really dead constant 2k ish rpms. After traveling at this really constant engine speed, the light came on. Let up to slow down for a stoplight, off it went. Wouldn't come back.

Called my pops, he said it's probably a sensor somewhere. Which figures. I'm guessing it's an O2 sensor, since it's past 150k miles and has been running a tad rich (according to gas mileage).

Otherwise no problems... just added a quart of oil. She burns about 1 quart every 3k miles.

Ghosty
04-27-2008, 09:27 PM
CEL will show up when the ECU detects any malfunction.
Some of them only show up only fraction of time and will disappear.
Some error codes are stored in the memory even after CEL is disappeared.
Try pulling the code.

Thanks for reassuring me about this -- like I said, it's just there and then it isn't.

Gary
04-27-2008, 10:09 PM
Check the error code.