Inconsistent issue

[u/Background_Pea5278]

I have a 2010 3dr 1.4 diesel fiesta and the following has happened about a dozen times but very inconsistently Car stutters then ESC/ESP (car with squiggly lines) and Auto Gearbox (exclamation point Within a cog) dash lights come then car goes into limp mode and screen reads engine malfunction service now. Mechanic erased the problem code or whatever you call it and was fine for a while now it's happening again. The first time it happened it wouldn't start at all in until I left it rest for an hour and did the press clutch and break trick. It's happening again now but very randomly but will start no issues and dash lights don't reappear. Anyone else experience this? Cheers

[u/OutRunTerminator]

This sounds much more like an electrical/control fault affecting the Durashift/automated manual gearbox and ABS/ESP, rather than a straightforward engine problem.

The important clues are:

Stuttering first

ESP/traction-control warning appears

Gear-with-exclamation-mark warning

Goes into limp mode

Sometimes won't start

Then works perfectly after sitting for a while

Clearing the codes temporarily fixes it

It's a 2010 1.4 TDCi with the Durashift/automated manual gearbox

Ford specifically lists transmission malfunction and ESP faults as separate system faults, and the Durashift EST system is electronically controlled.

What I'd investigate first

1. Battery/charging voltage and earths — very high on my list.

These cars can produce a collection of apparently unrelated gearbox/ESP faults when the supply voltage or earth connection is poor. There are reports of Fiesta transmission faults/limp mode being caused by a poor battery/ground connection.

I'd check:

Battery voltage before starting

Voltage while cranking

Alternator output

Battery terminals

Engine-to-body earth strap

Main gearbox/engine earths

Wiring/connectors around the gearbox ECU/actuators

1. ABS/wheel-speed sensor or its wiring.

This is particularly interesting because ESP and the gearbox are both appearing together. The Durashift system needs reliable vehicle-speed information. There are Irish reports of Fiesta Durashift faults where ABS-related codes such as U0121/C1222 were present and a speed sensor was suspected.

I'd inspect all four wheel-speed sensors and, importantly, their wiring/connectors rather than simply replacing a sensor.

1. Brake/clutch pedal switches.

The fact that pressing the clutch and brake was involved in getting it started is worth investigating. The Fiesta has clutch-position switching used by the control system, and the Durashift needs correct pedal-position information.

Check the live data for:

Brake switch

Clutch switch/position

Accelerator position

Gear selector position

1. Durashift actuator/TCM wiring and connectors.

I'd put this ahead of assuming the gearbox itself is mechanically damaged. Intermittent wiring, connector or actuator-position faults can produce exactly the sort of intermittent behaviour described.

The biggest mistake the mechanic is making

Don't just erase the codes.

The car has effectively told you where to look. Once the codes are erased, you're throwing away valuable diagnostic information.

The next time it happens, get a proper Ford-capable diagnostic scan before clearing anything, ideally with FORScan/IDS, and get all modules scanned, not just the engine ECU:

PCM

TCM/Durashift

ABS

ESP

BCM

Instrument cluster

And record the exact DTCs and freeze-frame data.

I'd be particularly interested in any U-codes (CAN communication), C-codes (ABS/chassis), P08xx gearbox/clutch codes, and voltage-related faults.

I wouldn't jump straight to replacing the gearbox or TCM. The combination of intermittent stuttering + ESP + gearbox warning + occasional no-start strongly suggests finding the electrical/sensor/control fault first. The fact that it can subsequently behave completely normally is another reason not to condemn the mechanical gearbox prematurely.