It keeps showing P0501 VSS code. What is the FCM ?

 

Front control module, also known as the PDC, Power distribution Center, it essentially is the Chassis Control Device for everything that doesn't involve the engine or transmission. The Factory Service Manual has all the wiring diagrams for the entire truck, and all the versions of it for that year.

 

large
leak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-497
p0456-evap purge system small
leak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-501
p0457-loose fuel cap . . . . . . . . . . . . . . . .9-505
p0460-fuel level sending unit no
change over miles . . . . . . . . . . . . . . . .9-1887
p0461-fuel level sensor 1
performance . . . . . . . . . . . . . . . . . . . . . .9-510
p0461-fuel level unit no change
over time . . . . . . . . . . . . . . . . . . . . . . . .9-1252
p0462-fuel level sending unit volts
too low. . . . . . . . . . . . . . . . . . . . . . . . . .9-1888
p0462-fuel level sensor 1 circuit
low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-514
p0462-low voltage detected at the
fuel level sensor . . . . . . . . . . . . . . . .9-1255
p0463-fuel level sensor 1 circuit
high. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1891
p0463-fuel level sensor 1 circuit
high . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-517
p0463-high voltage detected at the
fuel level sensor . . . . . . . . . . . . . . . .9-1259
p0477-low voltage on the engine
brake driver. . . . . . . . . . . . . . . . . . . . . .9-1262
p0478-high voltage on the engine
brake driver. . . . . . . . . . . . . . . . . . . . . .9-1265
p0480-cooling fan 1 control
circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-522
p0480-fan clutch . . . . . . . . . . . . . . . . . . . .9-1267
p0483-fan speed . . . . . . . . . . . . . . . . . . . .9-1272
p0498-nvld canister vent valve
solenoid circuit low . . . . . . . . . . . . . .9-526
p0499-nvld canister vent valve
solenoid circuit high . . . . . . . . . . . . . .9-529
p0500-no vehicle speed sensor
signal. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1280
p0500-no vehicle speed signal . . . . . . . .9-1896
p0501-vehicle speed sensor 1
performance . . . . . . . . . . . . . . . . . . . . . .9-533
p0503-vehicle speed sensor 1
erratic. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-538
p0505-idle air control motor
circuits. . . . . . . . . . . . . . . . . . . . . . . . . .9-1899
p0506-idle speed performance
lower than excepted . . . . . . . . . . . . . .9-543
p0507-idle speed performance
higher than excepted . . . . . . . . . . . . . .9-545
p0508-idle air control valve sense
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-547
p0509-idle air control valve sense
circuit high. . . . . . . . . . . . . . . . . . . . . . . .9-552
p0513-invalid skim key . . . . . . . . . . . . . . . .9-556
p0514-bat temperature sensor
rationality . . . . . . . . . . . . . . . . . . . . . .9-1284
p0516-battery temperature sensor
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-558
p0516-low voltage at the bat temp
sensor . . . . . . . . . . . . . . . . . . . . . . . . . .9-1286
p0517-battery temperature sensor
circuit high. . . . . . . . . . . . . . . . . . . . . . . .9-561
p0517-high voltage at the bat temp
sensor . . . . . . . . . . . . . . . . . . . . . . . . . .9-1290
p0521-oil pressure switch
rationality . . . . . . . . . . . . . . . . . . . . . .9-1295
p0522-oil pressure circuit low . . . . . .9-1904
p0522-oil pressure too low . . . . . . . . . .9-565
p0523-oil pressure circuit high . . . . . .9-1908
p0524-oil pressure too low . . . . . . . . . .9-1298
p0532-a/c pressure sensor circuit
low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-570
p0532-a/c sending unit volts too
low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1301
p0533-a/c pressure sensor circuit
high . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-575
p0533-a/c sending unit volts too
high. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1308
p0541-low voltage on the #1 intake
air heater relay . . . . . . . . . . . . . . . . . .9-1313
p0542-high voltage on the #1 intake
air heater relay . . . . . . . . . . . . . . . . . .9-1316
p0551-power steering pressure
switch performance. . . . . . . . . . . . . . . .9-580
p0562-battery voltage low . . . . . . . . . .9-1319
p0562-battery voltage low . . . . . . . . . . . .9-584
p0563-battery voltage high . . . . . . . . . .9-1323
p0563-battery voltage high . . . . . . . . . . . .9-589
p0571-brake switch 1 performance . . . .9-592
p0572-brake switch 1 stuck on . . . . . . . .9-597
p0572-low voltage detected at the
brake switch. . . . . . . . . . . . . . . . . . . . . .9-1326
p0573-brake switch 1 stuck off . . . . . . . .9-601
p0573-high voltage detected at the
brake switch. . . . . . . . . . . . . . . . . . . . . .9-1330
p0579-speed control switch 1
performance (5.7l). . . . . . . . . . . . . . . . . .9-605
p0580-low voltage detected at the
speed control switch. . . . . . . . . . . . . .9-1333
p0580-speed control switch 1
circuit low (3.7l,4.7l) . . . . . . . . . . . . . .9-613
p0580-speed control switch 1
circuit low (5.7l) . . . . . . . . . . . . . . . . . .9-617
p0581-high voltage detected at the
speed control switch. . . . . . . . . . . . . .9-1337
p0581-speed control switch 1
circuit high (3.7l,4.7l) . . . . . . . . . . . . . .9-623
p0581-speed control switch 1
circuit high (5.7l) . . . . . . . . . . . . . . . . . .9-629
p0582-speed control vacuum
control circuit. . . . . . . . . . . . . . . . . . . .9-635
p0585-speed control switch 1/2
correlation (5.7l) . . . . . . . . . . . . . . . . . .9-641
p0586-speed control vent control
circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-653
p0591-speed control switch 2
performance . . . . . . . . . . . . . . . . . . . . . .9-659
p0592-speed control switch 2
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-667
p0593-speed control switch 2
circuit high. . . . . . . . . . . . . . . . . . . . . . . .9-672
p0594-speed control servo power
relay circuit . . . . . . . . . . . . . . . . . . . . . .9-677
p0600-serial communication link . . . . . .9-683
p0601-internal memory checksum
invalid. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-684
p0601-pcm internal controller
failure . . . . . . . . . . . . . . . . . . . . . . . . . .9-1911
p0602-checksum error . . . . . . . . . . . . . .9-1343
p0604-ecm software error . . . . . . . . . .9-1344
p0606-ecm hardware error . . . . . . . . . .9-1345
p0606-internal ecm processor . . . . . . . .9-685
p0607-ecm internal failure . . . . . . . . . .9-1346
p060b-etc a/d ground performance . . . .9-686
p060d-etc level 2 app performance . . . .9-687
p060e-etc level 2 tps performance . . . .9-688
p060f-etc level 2 ect performance . . . .9-689
p061a-etc level 2 torque
performance . . . . . . . . . . . . . . . . . . . . . .9-690
p061c-etc level 2 rpm performance . . . .9-691
p0622-generator field control
circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . .9-692
p0622-generator field not
switching properly. . . . . . . . . . . . . . . .9-1347
p0622-generator field not
switching properly. . . . . . . . . . . . . . . .9-1912
p0627-fuel pump relay circuit . . . . . . . .9-696
p0628-low voltage detected at the
fuel lift pump . . . . . . . . . . . . . . . . . . . .9-1351
p0629-high voltage detected at the
fuel lift pump . . . . . . . . . . . . . . . . . . . .9-1355
p062c-etc level 2 mph performance . . . .9-700
p0630-vin not entered error . . . . . . . .9-1359
p0630-vin not programmed in pcm. . . . . .9-701
p0632-odometer not programmed
in pcm . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-702
p0633-skim key not programmed in
pcm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-703
p0633-skim secret key not entered . . . .9-1360
p0642-low voltage at the #2 sensor
supply circuit . . . . . . . . . . . . . . . . . . . .9-1361
p0642-sensor reference voltage 1
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-704
p0643-high voltage at the #2
sensor supply circuit. . . . . . . . . . . . . .9-1365
p0643-primary 5-volt supply
circuit high. . . . . . . . . . . . . . . . . . . . . . . .9-708
p0645-a/c clutch relay circuit . . . . . . . .9-1916
p0645-a/c clutch relay circuit . . . . . . . .9-711
p0646-low voltage detected at the
a/c clutch relay . . . . . . . . . . . . . . . . . .9-1368
p0647-high voltage detected at the
a/c clutch relay . . . . . . . . . . . . . . . . . .9-1372
p0652-low voltage at the #1 sensor
supply circuit . . . . . . . . . . . . . . . . . . . .9-1375
p0652-sensor reference voltage 2
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-715
p0653-high voltage at the #1
sensor supply circuit. . . . . . . . . . . . . .9-1379
p0653-sensor reference voltage 2
circuit high. . . . . . . . . . . . . . . . . . . . . . . .9-718
p0685-auto shutdown relay
control circuit. . . . . . . . . . . . . . . . . . . .9-721
p0688-auto shutdown relay sense
circuit low. . . . . . . . . . . . . . . . . . . . . . . .9-725
p0698-accelerator pedal position
sensor (apps) supply voltage
too low. . . . . . . . . . . . . . . . . . . . . . . . . .9-1382
p0699-accelerator pedal position
sensor (apps) supply voltage
too high. . . . . . . . . . . . . . . . . . . . . . . . . .9-1386
p0700-transmission control
system (mil request). . . . . . . . . . . . . . . .9-730
p0703-brake switch 2 performance . . . .9-731
p0801-reverse gear lockout circuit
open or shorted. . . . . . . . . . . . . . . . . .9-1920
p0850-park/neutral switch
performance . . . . . . . . . . . . . . . . . . . . . .9-737
p1115-general temperature
rationality. . . . . . . . . . . . . . . . . . . . . . . .9-741
p1195-o2 sensor 1/1 slow during
catalyst monitor. . . . . . . . . . . . . . . . . .9-1924
p1196-o2 sensor 2/1 slow during
catalyst monitor. . . . . . . . . . . . . . . . . .9-1927
p1281-engine is cold too long . . . . . . . .9-1930
6 dtc index dr/dh

 

Thanks Gone Fishing. I feared it was that.

 

Check your ground wires. I would loosen and retighten them.

 

I have crawled all over this truck. There has been 5 different techs all over it. I wish it was that simple. I traced all the wires and checked every ground I came to. P0501 keeps popping back up as soon as power is hooked back up.

 

I had an O2 sensor getting flagged, wasn't the sensor or the wiring.... I replaced the pcm with a used one from eBay, problem solved. I did have the dealer flash it so I could pass inspection (VIN is encoded in that thing).

 

I had a Dakota that did the same thing. Turns out bearings in the rear differential were letting the ring gear move as soon as I replaced them, problem solved

 

Some trucks have 2 wheel rear abs only....did you check the rear wheels?

 

There is a major harness connection located behind the drivers front wheel well, coming out of the engine bay. Pull the battery negative first, dissipate all energy, then open that connection block up and inspect it very carefully for any broken pin connectors, corrosion of any kind, also flex the wires on either side of the block, looking for abnormal bulging, or weak flexing. The wiring in many of the Dodges, and from what I'm hearing from others, is less than desired, in terms of being robust.
The door speaker and lock wires are a prime example---they have been known to break from flexing wear, and terminals on ecm's have been found to be corroded to the point of nearly falling off etc, etc. These very expensive vehicles we buy now have been engineered to the minimum design specs necessary for many of the systems. Copper these days, is almost like gold----you get the idea!