Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Diagnosis please?

I think you’re chasing your tail with the second brake light switch

My “best” remote assessment would be (with the lack of fault codes) would be either fuel pressure or a spark plug/HT issue. The Ford coil packs aren’t the most robust of beasties

But I’m hypothesising without being able to throw some test equipment on the car

Simon @ SiFab.co.uk

Sifabtemporary @gmail.com

Well I have a difficult loom diagram and have identified the wires from this second switch as black/white and black/yellow
These wires appear on the loom in a couple of places including BLACK/yellow to “LSCV” connector also to “PATS SUB HARNESS” and “RH PRE CAT GREEN”,
and black white seems to be a feed to/from the ecu, although there is a smudge which might be BW (or SW) to the handbrake switch

Anyone the wiser?

Meanwhile I’ll start worrying about Simon’s suggestion for which I’m very grateful

The best is to try it out while driving. If everything doesn't work out, think again about the throttle plug. I also changed the ignition coil and the spark plugs. In my case there was no positive change.

Perhaps the brake pedal switch’s functionality is configurable within the vehicle map so you may never really be sure how it is integrated for a given vehicle.

For what it’s worth here is a portion of the Focus 1.6 Ti-VCT diagram which I think is the donor….? I’ve found that Morgan usually stick to the original wiring (but not necessarily colours). The brake pedal sensor (normally open) looks like it just supplies 12v directly to pin 40 on the ECU.


S13 =Brake pedal position sensor
M12 = fuel pump
K20 = Fuel pump relay
B138 = Accelerator pedal posn sensor
A35 = ECU

Good luck with it

Good stuff thank you

The only thing I can think of for a second brake switch on a car is to de-activate cruise control when the brakes are applied. I know Morgans don’t usually have this feature but of course it’s an engine and ecu from the Ford stable, so maybe those bits are fitted as standard at the Ford factory and rather than amputate, are simply carried over when building the Mog? I am not fully convinced that the fuel supply on most cars is cut off when you apply the brakes; a bit of a red herring IMO.
I favour Heinz suggestion of throttle position sensor as a probable source of the original loss of power issue.

Hi SFG,

Yes that's right, while driving if the brake is pressed with the left foot while the right foot stays on the throttle the brake overrides the throttle and the car slows, power from the throttle is reduced, can't say whether it reverts to tick over or not as I released the brake prior to stopping, I do not drive in this way, I only found out this happened when I wanted to dry the discs and pads by operating the brake gently whilst driving, the brake overrode the throttle, hope this makes sense.
It definitely does it on both my mercs, I'm sure it did it on my roadster and plus 4, maybe someone on here can support this? (it is a few years now since I had a Mog and my memory is not what it once was)

I'm not suggesting that this is the cause of your fault, it was just another idea to look at.

Apologies...should have done some homework before opening gob! Exbiker sounds convincing so I Googled this and found “The car connection“ page on “businessinsider.com”
This was dated 2012 and focussed on Hyundai standardising on a brake- throttle over-ride becoming standard, though other manufacturers were already doing it. Reading further, they mentioned the Ford system termed BOA (brake over accelerator) This was first fitted in 2005 to the Ford Escape hybrid, but by 2010 was standard across all Ford models. It monitors brake and throttle action and if brakes are applied without a decrease in throttle movement, it immediately drives the throttle closed. Immediately on releasing the brake, the throttle will assume the previous setting.
BMW started doing it in 1988 and Mercedes in 2002.
Systems vary with some requiring accelerator to be applied for a couple of seconds prior to brake being applied etc
So I have learned something and apologies for not fully believing views of others on here.

Crikey, you’d think these things would be more common knowledge:

Rog: just a minor observation. The switch S13 in your diagram seems to be fed by green/brown, unless nomenclature has changed.
And , given the explanations above, it’s odd that I couldn’t activate the cut off albeit while stationary. I’ve done that brake drying thing on other cars as well and never noticed it, perhaps it’s imperceptible.


What is the throttle position sensor, is it part of the accelerator pedal? Would it have shown as a fault on the OBD? Might as well get one on hand ready, but I won’t change it until I know whether the fault is still there, I’m still hoping it was the brake switch that was upsetting things , although less likely now that I’ve learned all this.

When restrictions are lifted, I’ll see if it’s changed anything and then look at fuel and sparks. I imagine we’ll all be out there trying out the brakes!
Stay safe everyone and a big thankyou to NHS and carers.

The TPS throttle position sensor is part of the electric or mechanic throttle housing which also includes the butterfly, quite this item where I am talking about its plug.
Sensors such as O2 sensor or crankshaft position are immediately recognized as faulty because they are not primary inputs but because their behavior in combination with other information is recognized as incorrect, if so.
MAF sensors are a typical example when a fault is not detected. The ECU takes the value of the MAF sensor as it is. It is a primary input that cannot be compared to other sensors.

In my OBD, TPS was not detected as broken, but the value of the throttle on, off, on off, was displayed when running live data. But for the ECU it was the same as if I stepped off the throttle.

I don't know if Ford shows a broken TPS in the OBD. But...I am very sure that my TPS has always worked fine. It wasn't broken and it wasn't the culprit. I suspect very strongly the culprit was the wire that leads to the TB electric motor (but not the electrical motor itself because as I wrote I changed the whole item without a change before I suspect the plug).

Then the ECU interprets the TPS values not as a fault but in the same way as if I hadn't accelerated. At least it seems to be the case with Ford in 4/4 that the throttle position is not compared to the pedal position or something else which could be a mismatch and only then the ECU would have noticed an error.