Tail lights, license plate lights stopped working...

[brinkohio]

Last week I noticed that my tail lights and license plate lights don't work when the headlight switch is on. Rear turn signals work, flashers work, back-up lights work so the lamps are good. Fuses are good, relay is good. Here's the thing: I had installed a Hoppy trailer-lighting harness about 6 mos. ago. Even after removing it, my rear running lights and license plate lights still don't work. What should I try next?

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[brinkohio]

My bad, '02 Ram 1500, 4.7L, V8.

[bigjrussell]

I helped my buddy put on a trailer wiring kit and he had probelems with his truck later too. Except when he stepped on the brakes, the brake lights wouldn't work. The running lights and blinkers would work fine. I checked all the bulbs, all the fuses, all the wiring, and even uninstalled the harness and nothing fixed the brake light problem. His was a '00 5.9, though.

[blakusta]

I had the same problem last year, I had to replace the whole fuse box. It cost about $500. I tried everything else, i even tried to get into the fuse box but couldn't. I didn't have any mods done to the truck either. Hope that helps

[castleoz]

Having same problem here - does anyone have a suggestion within reasonable accomplishability?
I have checked the bulbs, fuses, relays, and wire harness, but to no avail. need help as I'm trying to move out of state and don't want to have to travel solely during the day. thanks

[Fraenkyboy]

I come from Germany, my speak is not so good....I have the same problem, mynormal light didn´t work. All other lights as brake and reargear and turn signals works ok.I have checked all bulbs and cables and relais but all this parts ok. But I have found that the "Park Lamp Relay" have no ground! If Itake manualy ground on the relais the lights work and the fuse 32 and 34 have power!!!!!!

In the the service manual is the next step the "Front Control Module":

FRONT CONTROL MODULE

DESCRIPTION

The Front Control Module (FCM) is a micro controller

based module located in the left front corner

of the engine compartment. On this model the integrated

power module must be positioned aside in

order to access the front control module. The front

control module mates to the power distribution center

to form the Integrated Power Module (IPM). The

integrated power module connects directly to the battery

and provides the primary means of circuit protection

and power distribution for all vehicle

electrical systems. The front control module controls

power to some of these vehicle systems electrical and

electromechanical loads based on inputs received

from hard wired switch inputs and data received on

the PCI bus circuit (J1850).

For information on the

Integrated Power Module

Refer to the Power Distribution Section

of

the service manual.

OPERATION

As messages are sent over the PCI bus circuit, the

front control module reads these messages and controls

power to some of the vehicles electrical systems

by completing the circuit to ground (low side driver)

or completing the circuit to 12 volt power (high side

driver). The following functions are

Controlled by

the Front Control Module:

²

Headlamp Power with Voltage Regulation

²

Windshield Wiper “ON/OFF� Relay Actuation

²

Windshield Wiper “HI/LO� Relay Actuation

²

Windshield Washer Pump Motor

²

Fog Lamp Relay Actuation

²

Park Lamp Relay Actuation

²

Horn Relay Actuation

The following inputs are

Received/Monitored by

the Front Control Module:

²

B+ Connection Detection

²

Power Ground

²

Ambient Temperature Sensing

²

Ignition Switch Run

²

Washer Fluid Level Switch

²

Windshield Wiper Park Switch

² PCI Bus Circuit

DIAGNOSIS AND TESTING - FRONT CONTROL

MODULE

The front control module is a printed circuit board

based module with a on-board micro-processor. The

front control module interfaces with other electronic

modules in the vehicle via the Programmable Communications

Interface (PCI) data bus (J1850). In

order to obtain conclusive testing the Programmable

Communications Interface (PCI) data bus network

and all of the electronic modules that provide inputs

to, or receive outputs from the front control module

must be checked. All PCI (J1850) communication

faults must be resolved prior to further diagnosing

any front control module related issues.

The front control module was designed to be diagnosed

with an appropriate diagnostic scan tool, such

as the DRB III

t. The most reliable, efficient, and

accurate means to diagnose the front control module

requires the use of a DRB III

t scan tool and the

proper Body Diagnostic Procedures manual.

Before any testing of the front control module is

attempted, the battery should be fully charged and

all wire harness and ground connections inspected

around the affected areas on the vehicle.

REMOVAL

(1) Disconnect the positive and negative battery

cables from the battery.

(2) Partially remove the integrated power module

from the engine compartment (Refer to 8 - ELECTRICAL/

POWER DISTRIBUTION/INTEGRATED

POWER MODULE - REMOVAL).

(3) Remove the front control module retaining

screws.

(4) Using both hands, pull the front control module

straight

from the integrated power module assembly

to disconnect the 49-way electrical connector and

remove the front control module from the vehicle.

INSTALLATION

(1) Install the front control module on the integrated

power module assembly by pushing the

49-way electrical connector straight in.

(2) Install the front control module retaining

screws. Torque the screws to 7 in. lbs.

(3) Install the integrated power module (Refer to 8

- ELECTRICAL/POWER DISTRIBUTION/INTEGRATED

POWER MODULE - INSTALLATION).

(4) Connect the positive and negative battery

The questions is, I have an ODB2 programmer but no software to check the FCM and PCM, did any know a software that works with the Dodge Ram 1500 4,7 or gives a other solution to reprogramming the PCM and FCM?

Best regards
Frank

[AlexisRam]

Hi all!

I am having the same issue with my park lamps Front and Rear. Checked everything (relays, fuses, etc.) park lamps only work if I jump the relay.

Fraenkyboy indicated that the FCM was the problem but I did not see a reply or update since the post. Can anyone advise? I am out of ideas here so do I change the FCM?

TO DATE I HAVE:
Changed headlight switch
Checked all relays
Checked all fuses
Checked all bulbs
Checked all connectors
Ckecked all chassis grounds
Verified 12v to relay (30, 86)
Verifiy relay working by applying ground to (85) and lights work


HELP!

[Lash]

Had the same problem here. Had to replace the under hood fuse box.

With this many problems all of a sudden (dealers actually have the boxes on back-order) you'd think a recall would be issued.

[abarmby]

Definately DEFINATELY...............it's the fuse box.
Do a search for the many items and replys I have made to describe and fix the "running lamp problems".
Replace the whole Power Distribution Module...............fuse box to you and I and your problem WILL be solved!
There are corrosion problems seated deep within the fuse box, where the printed circuit board paths connect the FCM to the fuse box internally. These corroded paths, cause high resistance to ground, which the FCM uses to turn on the Park Lamp Relay. The FCMcannot switch on the Park Lamp Relay because of this high resistance.
There is a description of how to jumper the Park Lamp relay, to temporarily force the rear lights to work as AlexisRamdid, when he connected pin 85 to ground of the park lamp relay.
This emulates what the pathways embeded deep in the fuse box do.
My posts have a long and thourough "How to" on that, along with decriptions of the fault etc.
I replaced my fuse box 18mnths ago, and no more problems. Instant fix.
It really is a VERY frustrating fault that is easy to cure but costs $ in a new fuse box/PDM.

Hope this helps?
Al.

[AlexisRam]

I appreciate all the feedback! I will pick up the fuse box today and let you know...keeping my fingers crossed!