zoomee99

Got a weird issue in my 97 LS 220K...maybe someone has run into this...light switch is off, I shut off the engine, pull the key, exit the car, when I close the door, the headlights turn on and stay on. Killed my batt last night.

Light switch seems fine, relays seem fine. My guess is the door ecu has gone bonkers so I've got one on the way via ebay.

Normal operation is the opposite, lights shut off when the door closes, so figure since the logic is reversed must be a ecu\computer issue. But thought I would post and see if anyone has run into something similar.

Yamae

The headlights relay is driven by the switch itself or the multiplex network body computer. It is an "OR" circuit and there are two ways to turn them ON. The multiplex network body computer is connected to the door computers through the communication bus called BEAN.

You are partly correct. You need to check these computers other than the switch and the relay.

zoomee99

Thanks for the reply. Guess I'll do the door ecu first, then the body if not fixed. Do you know of a source for the ecu schematics, might be fun to use my obsolete component repair skills.

zoomee99

My problem is back....97 LS with 225K. Headlights turn on when the ignition is off and driver door closes...killed my battery last night. Replaced the door ecu last time and that fixed it for a few months but the problem is back again. I swapped out the headlight relay, it's OK. So I'm thinking it must be the body ECU...Yanmae says the door and body ECUs share a data bus....since the logic is reversed I'm guessing an IC chip has failed....NOR instead of OR.

So I need some advice...

Online searching can't find a used body ECU. New ones cost $1000 so that is out. Any suggestions?

Is the body ECU involved with the security & immobilizer? If so it might not be a simple replacement.

Has anyone tried repairing these? I can deal with component replacement but some of these chips have teeny little legs, too small for these old eyes.

Thanks,

Jim

fixmiester

Yeah, I follow your logic...no pun intended. Finding I/C components is hard enough, especially if they were custom designs. Replacing them is even harder. Do your lights behave normally when the selector is in non-auto position? My turn off delay is defeated as long as any door, or trunk remains open, which is a good design. But yours appears to be working just the opposite, which would suggest a logic failure. Is it possible there is a N/O or N/C relay in the circuit that has stuck contacts?

RA40

iTrader: (6)

How is the light stalk? Which position is it left in when the car is shut off?

(Merging prior thread...with same issue.)

zoomee99

The lights come on by themselves, position of light switch has no effect. I found a body ecu online for $70 so I swapped it out. Problem is gone for now. So far I've I replaced both the door and body ecu, we'll see if the problem comes back.

Do you really need a data bus and two ecus to control the headlights!?! Geez. And this is a 16 year old car! I see the ads for the new LS with the automatic collision detection and a laundry list of whiz bang technology...no way those cars will last more than 10 years before half that crap is broken & in need of expensive repairs. I know they have to compete with the krauts in a tech arms race but it's kinda a shame they don't follow KISS design more often.

timmy0tool

iTrader: (7)

KISS haha, these are very complex cars with aging technology yet they are still a TON better compared to the cars built in the same time period. they remain very reliable even to today's standards.

this is the first i've heard of such a problem. would the light sensor on the dash be a culprit? anything block it? although i would think the switch stalk overrides it all.

Yamae

Things are often very much complicated. Without finding the root cause and a simple replacement will often cause a problem again. It often requires you to use complicated equipments to find out the root cause and it can't be done by most amateurs.

Other than that I worry about cables connected between those computers are not in good conditions especially at the door hinge.