2014 Transit 350 AWD terrain warning light - P2138 and U0401

[sythna]

You’re right, Mark. I did start going down that route and unplugged the MAF and accelerator pedal, but I gave up when I couldn’t confidently locate the throttle/air-doser sensor and didn’t want to start disconnecting random plugs.

The garage has now spent around 2–2.5 hours checking the loom and probing the sensor circuits, and they say everything they’ve tested is reading around 5V with no obvious wiring fault found.

They’re now pointing towards the injectors because it is smoking heavily and smells strongly of diesel. I’m still sceptical, though, because the self-revving started immediately after the accelerator pedal was unplugged and reconnected. I don’t want to start firing the parts cannon and spend hundreds testing injectors without properly explaining the P0653 or the timing of how the fault started.

[sythna]

A bit lost now. If I do go towards injector testing total with diagonistic, injector labour and testing is around £480.

[metalworker0]

How garages work ..well some of them .. cant find the fault .. clueless about it , find another fault, or create another fault from nowhere and get some money out of you!

You want a proper diagnostic tech , other than that, it's learn as you go! and experience the great sense of fulfillment when you alone, find out what it is and fix it yourself.

all the best......mark

[sythna]

Update on the Transit issue

Garage has now removed all 4 injectors and sent them for testing. The result has come back that all 4 injectors have failed. From what I’ve been told, 3 have failed both mechanically and electrically, and the 4th has also failed one of the tests.

The van was smoking heavily and smelling strongly of diesel, so this now makes more sense, but I’m still surprised that all 4 injectors have failed at the same time.

Before fitting replacements, I am asking the garage for:

- injector test report;
- checked for contamination, water or metal swarf

They’re quoting around £250 per injector, which feels a bit steep unless they’re quality recon/new units with warranty and coding included.

Question for anyone who knows these 2.2 Transits: if all 4 injectors fail, would you be checking the high-pressure pump/fuel system for contamination before fitting new ones? Also, does AWD make any difference to injector part numbers, or is it purely engine code/injector number based?

[sythna]

Quick update on this fault.

The injector route has now been followed. All 4 injectors were removed, tested and reported as failed. Replacement injectors were then fitted and coded, but the original accelerator/pedal issue is still not fixed.

The van now smokes badly, which it did not do before the injector work, so I am also wondering whether there could now be an injector coding, calibration, installation or fuelling issue on top of the original fault.

One important thing that was noticed: if the brake pedal switch/sensor is unplugged, the self-revving stops and the van becomes driveable enough to move. As soon as the brake pedal switch is plugged back in, the revving behaviour returns.

Since then, another auto electrician has tried a replacement ECU/PCM and coded it. With the replacement ECU, the uncontrolled revving behaviour changed, and strangely with my original ECU it has now also stopped revving uncontrollably. However, the main fault remains: the van starts and idles, but there is still no accelerator response. The APP live data is not being recognised properly by the PCM.

Another strange symptom is that when I press the brake pedal, the RPM drops to around 800 and the smoke settles. When the brake pedal is released, the RPM rises to around 1,000 and it smokes more.

Current key points:

* Original fault was P2138 throttle/pedal position correlation.
* Later/current fault is 5V reference circuit B too high.
* Accelerator pedal has been changed more than once.
* At the pedal connector, I have two 5V feeds present, but the other signal wires are currently showing 0V.
* Earlier, with the pedal disconnected, I had two 5V wires, one around 3V, and two near 0V.
* Another Mk8 owner tested theirs with the pedal unplugged and confirmed it simply ticks over with no throttle response. Mine previously revved itself to around 2,500 rpm with the pedal unplugged, so that does not appear to be normal failsafe behaviour.

I now have the APP wiring diagram. From what I can see, the accelerator pedal connector C2040 does not go directly to the PCM in one uninterrupted run. It goes through an intermediate connector C139, then to PCM connector C1232B.

The APP wiring appears to be:

* C2040 pin 1 — 5V reference 1
* C2040 pin 2 — APP1 signal
* C2040 pin 3 — return/ground 1
* C2040 pin 4 — return/ground 2
* C2040 pin 5 — APP2 signal
* C2040 pin 6 — 5V reference 2

Does anyone know where C139 is physically located on a 2014 Mk8 2.2 Transit?

I want to inspect it for corrosion, pushed-back pins, damaged wiring, or previous wiring modifications.

Also, any guidance on what the auto electrician should test next would be appreciated. My thinking is:

* load-test all 6 APP wires from pedal plug C2040 to PCM connector C1232B;
* inspect/check the intermediate C139 connector;
* check whether any sensor on 5V reference circuit B is pulling the circuit high;
* check brake switch/clutch switch inputs because unplugging the brake switch changes the revving behaviour;
* confirm whether the new smoking issue is injector coding, injector installation, fuelling correction, or something disturbed during the injector work.

Any pointers would be appreciated. I am trying to avoid more parts being changed without finding the actual cause.

[metalworker0]

What if the turbo was goosed and its intermittently running the engine on engine oil.

Not looking at all your complaints .. best going through this; one item at a time


all the best.mark

[sythna]

They said the looked at the turbo and don’t see any excessive oil. The uncontrolled revving was definitely electric as it went when you disconnect the brake sensor, and came back when you plugged it back in. This then went away with the new ECU, and would come back with the original ECU. Post updating my ECU to original Ford files somehow now fixed the issue on both the new and old ECU. The brake sensor new issue now is if you press the pedal the revs drop to 700-800 and when unpressed it’s 1000 and van smokes. In all situations APP1 and APP2 signals show 0 on PID.

[metalworker0]

well i sought of know there is an anti-stall switch on the clutch pedal that increases the revs momentarily.. what if the wires for this switch were mixed up with the brake one .. is that possible?

all the best.mark

[sythna]

well i sought of know there is an anti-stall switch on the clutch pedal that increases the revs momentarily.. what if the wires for this switch were mixed up with the brake one .. is that possible?

all the best.mark

Not sure if that’s the cause. When you press the clutch pedal it reads as clutch (CPS and CPP on the PID), and same for the brake pedal (BOO PID in forescan)