2003 Mercury Grand Marquis Headlights

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  #1  
Old 10-20-10, 01:27 PM
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2003 Mercury Grand Marquis Headlights

My headlights come on and then shut off without warning while driving.'
Since all other lights work fine I assumed it was a faulty switch in the dash. I replaced it with new, and still have the same problem. Any ideas??
 
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  #2  
Old 10-20-10, 04:41 PM
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Failure of the “LCM” (lighting control module) is common on your car.

Test as follows.

When the issue is happening check fuses 6, 15, 21, 23, and 27. Fuses 21, 23, and 27 should be hot all the time.

Fuses 6 and 15 should be hot only when the key on. If the above check out access the LCM. The LCM is under the steering wheel, on the passenger side of the steering column.

Disconnect connector C2145b. This is the sixteen terminal connector that has round pin-type terminals coming off the LCM.

Jump battery voltage to the Gray wire at pin number 10 of C2145b connector. Watch for the headlights coming on. If they don’t come on, then the gray wire circuit is open between the LCM and the multi-function switch. Repair as necessary. Note that replacement of multi-function switch may be necessary.

If the headlights do come on when voltage is jumped to the Gray wire, go to LCM connector C2145c. This is the connector that has spade terminals.

Check for battery voltage at the White/Violet wire at pin number 1 of C2145c connector. This is coming off of fuse number 15.

Now check for battery voltage at pin number 9, Red/Yellow wire, coming off of fuse number 15 and 6.

If voltage is present, go to connector C2145b, and check for battery voltage on the Tan/White wire in pin 12, coming off of fuse 21.

There should also be battery voltage on the Light Green/Yellow wire in pin 1, coming off of fuse number 23.

There should also be battery voltage on the Orange/White wire at pin number 6 coming off of fuse number 27).

Confirm good grounds, at the black wires at pins number 4 and 9 of C2145b connector. Grounding takes place at G201, behind the passenger side kick panel.

If LCM voltage and grounds are operational, turn the headlight switch on, and confirm ground from the headlight switch, Red/Yellow wire at pin number 10 of C2145c. If all is confirmed, then reconnect all connectors. If issue is still present, replacement of the LCM is necessary.
 
  #3  
Old 10-20-10, 08:03 PM
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Sam...

Is that the replacement for the old style GEM controller??????

I guess Ive been at Chrysler too long, as I would be looking at Forward control module, or BCM.
 
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Old 10-21-10, 08:50 AM
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Sam...

Is that the replacement for the old style GEM controller??????


Sure is buddy. GEM used to control:

Interior lighting
Daytime Running Lamps
Remote keyless entry
One-touch down driver's side window
Four-wheel drive
Battery saver
Heated rear window
Perimeter anti-theft
Warning chimes and warning lamps
Illuminated entry with remote keyless entry
Windshield washers and wipers

Motorcraft did away with the GEM because independent mechanics everywhere were figuring out how simple it was to diagnose and determine a failure with it. Service departments were losing money, because they were losing a major scam. That being, the rip-off diagnostic charge associated with determining a failed GEM. Watch. Won’t be long before they do away with the LCM for the same reason. LCM is a little bit more complicated, but nothing that the "ASE MASTERS and UNCLE DIEZEL’S" of the world can’t figure out.
 
  #5  
Old 10-21-10, 08:58 AM
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Thanks ASE MASTER for the detailed troubleshooting guide, but as of today I can not replicate the fault. The headlights are working fine for now. I will have to do some "daylight" driving to see if the problem returns.
 
  #6  
Old 10-21-10, 06:55 PM
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oy, that now sounds like either a loose wire or moisture collecting somewhere. heavy rains as of lately, that stopped?
i mean, if the problem is temperamental, it's a loose wire or moisture collection.
 
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