[RedSector]

Can you provide the engine designation code, positions 6,7,8 of the VIN.

 

[RedSector]

Looking through, common thread open circuits. Check the earth to the engine,bsi,ecu and the abs are all in good nick and check for resistance anything above 1 ohm (point to point) would suggest bad cable.

Also check battery terminals themselves.

 

[RedSector]

That's not a likely cause. The use of ballast resistor is because that system is monitored and the lights provide a known load. Even if this was the case, it would only throw out the systems involved and none your DTC code are evenly remotely close to these systems.

 

[RedSector]

I have access to Peugeot FSM and Haynes Pro to name a few resources.

P1303 appears to be a calibration error of EGR from search on the internet.
P1304 no idea but likely above, if the above is true.
My data from Haynes Pro suggest the above two codes are not part of your vehicle, so there is that, but it is not always right about these things. Had this happen with 4007 recently and knew it was wrong and went to Mitsubishi FSM to get the codes/fix.

DTC P1404 has multiple causes, is a confirmed DTC code, and is where I would start:-

EGR circuit range/performance, closed valve
Engine control unit additional heater circuit 2 and preheating circuit
Glow plug control unit 1
Air temperature sensor 2 circuit/open

Possible causes are
(1) EGR control solenoid with position sensor
(2) Glow plug control unit
(3) EGR control solenoid
(4) Engine control unit

I've made assumptions based on the other codes you cleared, there is an earth issue (which maybe wishful thinking if you didn't find any problems and actually checked it out correctly), but it could be power supply side. If we get to (4) ECU it is going to be harder to follow than normal, it does not have all the data about the pin locations in the harness, but details the pin use. I already suspect the ECU pins/connectors potentially are a source issue.

Can you use multimeter and read/follow testing steps ?
Example:-

 

[RedSector]

What is TCS/ABS DTC codes coming up?

that won't clear

Clearing DTC without repairing the cause is not really fixing anything, more wishful thinking. DTC codes don't *normally randomly appear without detected problem in the first place.

*exceptions are low battery state or charging fault, which will trigger random DTC codes.

 

[RedSector]

My wishful thinking is that it might be an earth problem in this.
Intermittent DTC faults will clear, but over time if detected again appear. Permanent DTC fault will not clear or clear and found almost immediately again. The status codes of them are provided from Lexia in the software. DTC will go historic if no longer found to be active.
Anyway, let's deal with one, I have information for.

DTC P1404 characterised as
EGR circuit range/performance, closed valve
Engine control unit additional heater circuit 2 and preheating circuit
Glow plug control unit 1
Air temperature sensor 2 circuit/open

Possible sensors/wiring in play
(1) EGR control solenoid with position sensor
(2) Glow plug control unit
(3) EGR control solenoid
(4) Engine control unit – I will cover if (1),(2),(3) test out ok or if E1 comes up in testing thereof.

(1) EGR control solenoid with position sensor

 

[RedSector]

(2) Glow plug control unit

(3) EGR control solenoid