Maybe someone here can help me out. I have a 98 GMC 1/2 ton pickup and whenever I tow my boat for at least 30 minutes, my check engine light comes on. After I disconnect the trailer and drive another 30 minutes or so the light goes off. I believe the problem has something to do with the trailer lights, although all the lights work just fine. It doesn't happen when I pull 2 of my buddies boats or my 16 ft flatbed trailer. Any body have any ideas? I'm totally lost on this one.

Does it come on even if you are not moving??? Turn on the engine and lights and let it idle for a while and see if it happens. Either way try to get a code out of it. A lot of auto repair web sites explain how to read the codes with a simple meter. Also most Chilton manuals explain it too. Or you can get a reader from Wal-mart or Pep Boys I think.

Do you have brakes on your trailer? If brakes are misadjusted, it could be putting a heck of a load on your trannie, causing it to overheat.

Other than those things, beats me???

SteveG

[This message has been edited by Steve G (edited 07-26-2002).]

It stays on as long as the boat is hooked up. What really has me confused is that if I pull my friends Ranger, another friends Stratos or my flatbed, it won't come on. Only when I pull my boat.

Hmmmmmmmmm!!!!!!!!!! This is a tough one. The only thing I can suggest is to go over every inch of the trailer wiring and visually inspect it for cracks, brakes or rubbing marks. I know the lights work fine, but you could have just a small wire, like a hair, touching something it's not supposed to. It may be just enough to trigger the warning light but not blow a fuse. Ain't modern technology great!?!?!? Them fancy electronics is so smart!!!

You have a '98 truck and I assume it has a four wire system for the trailer lights, is the trailer a four wire system? By that I mean are the brake lights and turn signal lights the same bulb or is it two bulbs or one bulb with two filiments?

At this point it's just a guess?!?!? Let me know what you find.

SteveG

Bankbeater,

How old is this trailer? And what part of Dallas do you live in?

I thought of some thing else! Check the bulb sockets real good and make sure they are good and watertight and clean! Had a short once in a light that was caused by rust. Now thats some rust baby!!( best Austin Powers voice)

Oops! Thought of another thing to try. Have you tried your trailer on one of your friends trucks????

waiting patiently,
SteveG

[This message has been edited by Steve G (edited 07-26-2002).]

Thanks for your suggestions Steve. Yes they are both 4 wire. I just put new lights on the trailer last winter and haven't had any problems until 3 weeks ago. Guess I'll pull all the wires and see if something is poking through.
The trailer is an 82 and I live in DeSoto.
Yes Sir, technology is GREAT!

DESOTO!!!

Man, that's like the other side of the world from me. It would take a lot of cold beer to get me to drive that far to check this out!!!!!! Not that you asked me too!!

Besides, it's Friday and it's quiting time and I have a date with some sandies this evning.

Do let me know what you find or if you need some more....ahem....help!!

SteveG

Man, I'd drive a 100 miles for a 6 pack. Seems I'm always the one buying and never any freebies.
I'll let you know. If I can't figure it out, maybe we can plan a double date with them sandies and see if you can figure it out.

Change your oxygen sensor. Its attached on your exhaust manifold. They tend to act up during high load conditions. And there about 20 bucks at a parts store.

Bankbeater,

Did you get your problem fixed??? molossusri had a good idea. But of course this would be in the codes of the computer, if we could just get a code......

Let us know???

SteveG

I didn't have time to mess with it this weekend. I fished Twok out of my buddies Ranger and the light never came on. The o2 sensor was a good suggestion but I sucpect if that was it it would come on no matter what I was pulling.
It has got to be a nick in a wire somewhere. At this point, it will probably be worth my while to drop $20 at Wallyworld and just change everything out.

I am no GM expert, but I would have to go with Molo's answer on this one. The Check Engine warning system could care less about your trailer lights. If the wiring to the lights electrically shorted, the tail light fuse would blow as designed. You need to think about what is being monitored by the Check Engine system. Oxygen and mass air flow I think are, and somehow control the fuel air mixture ratio. Is your boat and trailer weight heavier than your freind's Ranger and your flatbed trailer? Are your trailer brakes hanging up? If you don't have trailer brakes, do the wheels turn freely? Just a few ideas that might help in finding the problem. Bob

Thanks for the input Bob. My boat is a lot lighter than the Ranger and the trailer is not equiped with brakes. Like you, I didn't really think a lighting problem would cause the light to come on. What has me so baffled, is that i KNOW the trailer has something to do with the problem. It's almost time for a bearing job so I can jack it up and see how freely the wheels are spinning. The o2 sensor is cheap and takes no time to install, so I will go ahead and change it out also.
Keep the suggestions coming.

bankbeater

Well if you didn't spend so much time fishing and more time working on your stuff..............holy cow, what am I thinking?????

Sorry!

If we just didn't have to work, huh?

SteveG

You were sounding like my wife there for a minute. She asks: " What are you doing this week?" Hmm, working mans tourney at Pool on Tues, TFF tourney on Thurs, Club tourney on Sat.
Shoot, I just realized I don't fish enough. I'm missing out on 4 days every week!!