What are the symptoms of a bad PCM?

U1900 FORD - CAN Communication Bus Fault

Read more: https://www.autocodes.com/u1900_ford.html
Possible causes
Faulty / intermittent ignition switch connections
CAN Bus wiring intermittently open/shorted to power or ground Faulty / intermittent connection at PCM
Faulty electrical connections at ABS Control Module
Faulty electrical connections at the instrument cluster
Poor connections at the trailer brake controller/trailer connector

Tech notes This is typically a false/intermittent code. It can occur if: Someone hooks up a scanner to the OBDII port while the ignition is on or while the engine is idling. A trailer brake system is installed improperly/incorrectly on a truck with ABS (anti-lock brakes).

When is the code detected? When the PCM, Brake Controller and Instrument Cluster are unable to communicate with each other at any time while the ignition switch is turned to the "Run" position, code U1900 sets in memory.

Possible symptoms Engine Light ON (or Service Engine Soon Warning Light) Amber ABS (Anti-lock Brakes) Light ON Wrench Light On

U1900 Ford Description The Anti-ock Brakes System (ABS) module, the Powertrain Control Module (PCM), and the instrument cluster communicate over the Controller Area Network (CAN) Bus. This is a high-speed bus communication system and is not fault tolerant, which means any type of intermittent/loose connection between these 3 controllers will cause communication to stop. When the PCM, ABS module and instrument cluster are unable to communicate with each other at any time while the ignition switch is turned on, code U1900 will set.

Read more: https://www.autocodes.com/u1900_ford.html

Have you had the vehicle checked for DTC'S - diagnostic trouble codes ? I would start there first . Battery , charging system all good ? What computer , the ABS has a control module all to it self . The Air con has a relay in the under hood fuse box controlled by the PCM / engine computer . If there is a problem with ABS , The EBCM - electronic brake control module will turn on ABS and the red brake light .
A low voltage condition could cause this problem , but I would expect more of the lights to be lit on the dash . Including the check engine light , battery light . This are not connected , Power or ground wise . Have the vehicle checked for codes , that should be the first place to start any diagnostic's always !

Not sure about the Honda setup, but when my Dakota had those lights both lit, it was a bad speed sensor in the system. I had the additional symptom of no speedometer reading until about 30mph.
It seems that the VSS in my system was used at lower speeds by the ABS system to determine when to activate. If the ABS light goes on, many vehicles will also activate the brake light since the two are undoubtedly related.

You have too many too many things going on to give a good diagnoses. It really needs to go on a scanner. My best guess, is the instrument panel is bad.

Could be. But these are also symptoms of a bad ground wire. Check the engine to body ground.

ABS = Anti-lock Brake System.
TC = Traction Control System (Engine Control Module).
If the ABS lights on the dashboard permanently the ABS system is faulty. You must access the ABS & TC Electronic Control Units (ECU) memory for pull out all DTC (Diagnostic Trouble Codes), using diagnostic equipment connected to the data link connector of the car. Then you will be full informed about bad pieces (e.g.: front right wheel abs sensor interrupted, ...). After bad pieces replacement you will be able to erase all faults memored by ABS ECU, in other words reset the ABS system and turn off the warning lamp on dashboard.
I suspect bad brake pedal switch, but you should scan the ABS & TC ECU's.

CHECK ALTERNATOR OUTPUT.MAKE YOUR VOLTAGE OUT PUT IS 13.5 TO 14.5 VOLTS.IF NOT ALTERNATOR BAD IF ALTERNATOR GOOD THE DEALERSHIP HAS TO HOOK CAR TO DIAGNOSTIC TO CHECK THE ENGINE PCM CONTROLS AND ABS BRAKES AND TRAC.SYSTEM.REASON I SAID ALTERNATOR BECAUSE I SEEN ALTERNATOR GO BAD UNTIL IT OUTPUT WAS LOW CAUSING CHECK ENGINE LIGHT AND ABS LIGHT TO COME ON.

You will need to have the pcm scanned to pull the trouble codes ffrom this unit to get a better idea on what is going on. With the breaks I would say whoever changed them disturbed one of the wheel sensors for the ABS.

The traction control system is controlled through the Anti-lock brake system. The way it works is if one of your wheels starts spinning the ABS applys the brake to that wheel to transfer power to the oppsite wheel that is getting traction. If your ABS is bad then your Traction control won't work. To check it I would find a parking lot on a wet day. In an open space mash in the gas. if you hear the ABS system kick in and you don't squall the tires then your good. My guess is you won't. What I would be worried about is will my ABS work. When checking the traction control is a good time to check the ABS. Acclerate to around 15 mph, then mash the brake as your live depended on it. If you hear a motor run and feel a vibration or grind in the brake peddal, then it works.

The only way to know axactly what happen is with a diagnostic computer.
Because the ABS use a Speed sensor on each of the wheels.
Hydraulic selenoids on the ABS box or Module..
If the light is on. its mean the Anti Lock Brake System is inactive., You gonna brake like any car with no ABS.
I hope this information work for you.