# Trouble light, but no trouble **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** mercury, grandmarquis\ **Created:** [February 12, 2012, 2:10am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899 "2012-02-12T02:10:52Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Ben\_Hurt](https://avatars.discourse-cdn.com/v4/letter/b/258eb7/32.png) [@Ben\_Hurt](https://community.cartalk.com/u/Ben_Hurt)\ **Post date:** [February 12, 2012, 2:10am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/1 "2012-02-12T02:10:52Z")
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? ---
**Author:** ![Ben\_Hurt](https://avatars.discourse-cdn.com/v4/letter/b/258eb7/32.png) [@Ben\_Hurt](https://community.cartalk.com/u/Ben_Hurt)\ **Post date:** [February 12, 2012, 2:11am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/2 "2012-02-12T02:11:58Z")
Mistake. Didn’t mean to write anything here. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [February 12, 2012, 2:18am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/3 "2012-02-12T02:18:44Z")
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. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [February 12, 2012, 2:32am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/4 "2012-02-12T02:32:41Z")
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. [http://www.extreme-check-engine-light-codes.com/Ford%20OBD1%20Decoder.htm](http://www.extreme-check-engine-light-codes.com/Ford%20OBD1%20Decoder.htm) 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. Tester ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [February 12, 2012, 2:36am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/5 "2012-02-12T02:36:49Z")
Use the instructions Tester posted. Get the codes. Post them. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [February 12, 2012, 6:19am UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/6 "2012-02-12T06:19:05Z")
As long as passing an emissions test is not an issue, DRIVE ON!! Or you can visit [www.crownvic.net](http://www.crownvic.net), 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… ---
**Author:** ![jim-bob](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@jim-bob](https://community.cartalk.com/u/jim-bob)\ **Post date:** [February 17, 2012, 3:58pm UTC](https://community.cartalk.com/t/trouble-light-but-no-trouble/70899/7 "2012-02-17T15:58:03Z")
disconect the neg.side [black wire] of the battery for 30 seconds than reconect the wire.