90' 240 DL

Hey, guys, I just bought another brick for $550 and it just needed a power regulator to get going. I've been doing maintenance on it as the speedometer stopped at 227k, but there's one thing that's been stumping me. It has a check engine light, but the codes show 1-1-1 on both banks. I've cleared the codes, but that didn't do anything. Resetting the battery doesn't do anything either, the CEL light is immediately on along with the service light which goes away. There are no symptoms as it idles and drives flawlessly, if anything, it drives really, really well.

The only known issues to me is the driver side head lamp not working, and the exhaust-to-airbox hose has broken off, but would this cause an immediate CEL if it's not detecting hot air?

I'll be driving to a pick-and-pull this morning to round up some exterior parts, wish me luck!

 

that exhaust preheater hose does nothing useful unless you live in an extremely cold climate. in fact, the thermostat flap in the airbox often sticks open, which causes hot air to be dumped into the intake path when its NOT super cold, so its best wired shut

now, California smog stations will visually inspect that hose and not pass you if its missing, but I've never had them check the flap in the bottom of the air filter box.

 

Is it a check engine light or a service light? The service light is just a reminder based on the odometer and will turn on every 7500 miles. On the '90s models the service light is reset by using a pen to press the small button in the lower-right corner of the instrument cluster.

If it is the check engine, check codes for both the ECU and ICU.

 

Can anyone tell me how to reset the service light on an 86 740 turbo. It comes on just after starting but goes off after a minute but my smog shop won't test it until it goes off immediately.
Thanks.

 

It's on the back of the instrument cluster, pull it out, near the speedo there is a plunger you have to push. This light has nothing to do with emissions but the modern shops don't know much.

 

yeah, that SERVICE light is just a 5000(?) mile counter that is suggesting its time to change the oil.

 

Thanks guys. I tried to explain the difference to the smog tech and he kept telling that any "warning" light could not illuminate. Can't argue with stupidity.
So, I did pull back my dash console and without unhooking any wiring, was able to push the reset button.
I reassembled the console carefully and started up the engine to test. Unfortunately, now none of the gauges work except the engine temp. No fuel, alternator, tach, and now even the speedo doesn't work.
I pulled it back apart, disconnected all wiring to totally remove the console for inspection. No clear damage or wire connection issues. I cleaned the contacts where accessible.
I reassembled, started up the engine and wiggled all connections, wiring harnesses, etc and still no success.
I checked to see if any fuses or relays could affect it but nothing in fuse box that would lead me to success.
Any ideas guys?

 

Well, it pretty much has to be that a wire got dislodged somewhere during the process. There is no fuses or relays involved. Odd that the temp gauge would work and nothing else. Check your work again, you missed something.

 

Thanks Lev for responding. The strange part is just resetting by pushing the button but not disconnecting anything and still having this failure.
I've wiggled and jiggled the wiring harnesses, plugs, and connectors to no avail.
If worst case, I'll drive it knowing the temp gauge is really the most important gauge. Sure would like to see the amp gauge too.
Not sure if the oil light works but we'll see.
Updates to follow.

 

The saga continues.. Put everything back after verifying 12v in the harness at several points. Now nothing works still except the temp gauge and the 3rd gear arrow light works after years where I thought it was burned out.
As I drove it, now the battery light is illuminated, however, checking the battery, it's still charging at 13.4 volts.
When I press the 3rd speed button on the shifter, the tach starts to work. Crazy!
I think I have a poor grounding issue but not sure where to start. I'll keep on digging.

 

Very strange. Most cars don't have an amp gauge, now or then, but regardless, gotta solve this thing, it'd bug me to no end!