Trouble light, but no trouble

Bought a '95 Marquis with 60K miles, and trouble light soon came on. Mechanic #1 charged $300 for “downstream sensor.” Trouble light came right back. Go to mechanic #2 who says upstream sensor should be replaced. Mechanic #3 says the problem is the computer and wants $500. Only paid $2600 so we keep driving it for well over a year with no problem, and decent gas mileage. So, why bother? Drive it until it drops or spend the money?

Mistake. Didn’t mean to write anything here.

I suppose you could buy a surplus ECM for less, unless #3 wants to sell you a surplus unit. In older cars, it is sometimes oxidized connectors. You might try removing the connectors and cleaning them with contact cleaner.

BTW, what OBD-II codes did the mechanics see when they investigated the problem? When you say upstream and downstream sensors, I think of oxygen sensors in the exhaust pipes. But that might not be correct. If you don’t have the codes, you can borrow an OBD-II scanner from a local chain parts store and read them for yourself. It’s free. You leave a credit card with them while you use the scanner and they will print out the codes for you and return your card.

Your vehicle has the OBDI engine management system. Not OBDII. So an OBDII scanner from a parts store won’t work on your vehicle. Here’s how to pull the codes from a Ford with the OBDI engine management system.

My expeirience has shown that when a Check Engine light comes on, but the computer doesn’t spit out any codes, it’s usually a problem with the computer. You could contact a local auto recycler and see if any has a replacement computer for your vehicle.


Use the instructions Tester posted. Get the codes. Post them.

As long as passing an emissions test is not an issue, DRIVE ON!! Or you can visit, 4.6 Powertrains, and learn how to pull the trouble code yourself, and what that code means, and go from there…If the CEL annoys you, put some black tape over it…

disconect the neg.side [black wire] of the battery for 30 seconds than reconect the wire.