Intermittent Electrical/Turn Signal Issue

[jollypanther]

Hello,

I am having an intermittent issue with my 2003 Lincoln Town Car. Shortly after replacing the rotors and pads on all 4 corners when I used the turn signals the ABS light would come on and the ABS would pump. That has went away and now sometimes when I use the turn signals, either left or right, the entire instrument cluster lights up and the LCM starts buzzing like crazy. If I fail to shut the turn signals off within a few seconds. The ABS will disable, the Power Steering will go out and the HVAC and controller will die. Eventually the Instrument Cluster will black out and will do a full sweep reset. Furthermore, if I move the shifter at all the Instrument Cluster will again completely shut off then reset. Sometimes the instrument cluster reset will resolve the issue for a time, sometimes it will not. It appears to happen completely at random but happens at least once every 2 drives, it will last about a drive or two then go away. Below is what I have done to try and resolve this issue in order, I have access to All Data diagrams and ForScan and have been a shade tree mechanic for half my life with multiple full car restoration/engine/transmission/differential builds so I’m not completely ignorant…I think…

• Checked all relevant grounds to the circuits involved and nearly every irrelevant ground (All good)
• Alternator appears to provide good Voltage 13-14.1V
• Pulled and cleaned all interior fuses (All good)
• Replaced the Multifunction Switch (No Change)
• All exterior lights checked (All good, No Change)
• Battery Voltage was quite old and at 11.6v so I replaced it with new at 12.6v. (Problem seems less frequent)
• Replaced the LCM with a good used one. (Problem still there)
• Removed the Instrument Cluster entirely. (Problem still there)
• Removed the Radio (Problem still there)
• Removed the HVAC controller (Problem Still there)
• Removed the clock (Problem Still there)
• Removed the Dimmer Switch (Problem Still there)
• Removed the Headlight Switch (Problem Still there)
• Driving with All of the above besides the LCM (Problem Still there)
• Pulled fuses while problem present. Fuse 31 solves the issue but bypasses the flasher functionality
• Used ForScan to set the LCM settings back to Factory (waiting to see)
• Watching the LCM input voltage while driving. It fluctuates from 13-14.4V depending on what lights I have on (waiting to see)
• Watching the PCM Alternator Desired Voltage (waiting to see)
• Watching ABS reported speed (waiting to see)

I am looking for any recommendations or any help at this point. It is greatly appreciated.



-Jolly

 

[StratosFear86]

Can you pull codes from the ABS system on a `03? That should have been one of the first things to do. I would also invest in a factory service manual set, in that you should have a diagnostic flow chart that can really narrow your issue down. Wiring schematics too.

My scientific wild ass guess based on 80`s/90`s GM cars would be a failing ABS module or some corrosion/wiring shorting together.

 

[Action]

Interesting.

A typical issue with the turn signal on any vehicle is a poor ground. This poor ground connection may be poor or non-existent.
However the turn signal system is connected to a lot of other systems. Typically via the multifunction switch.
Brake light
Running lights
Horn
Sped control
ABS
Because of this the turn signal system will continue to seek a ground. EVEN if it means finding a ground from a different system.

I would suggest to (re) check grounds at the four corners of the vehicle for the exterior lamps. (turn signal) Generally the ground connection can be shared with other functions.

The other thing to do is tracing circuits and the power and ground for the circuit. Meaning start at the fuse with the known voltage. Then check the voltage in that circuit in as many connectors as possible. Then to the load (in this case a light bulb) and finally check the resistance from the bulb to the ground. (With the power turned off) TO do this you will NEED the factory wiring diagram.

Just a suggestion.

Action

 

[driller]

... Shortly after replacing the rotors and pads on all 4 corners ...

Hmmm... that in and of itself seems highly incriminating.

Over the years, I can tell you a few of my repair excursions have had inexplicable results. Used to be I would tear into something fearlessly without concern of collateral damage. Now, I often hesitate to try to repair something if it involves removing or otherwise disturbing multiple other items. Particularly fragile aging components and especially so with plastic parts and wire harnesses.

That being said, a simple 'brake job' should not incur such a problem but I would not be surprised if an ABS sensor or harness issue resulted in the cascade of symptoms.