Ford Focus 1.6 TDCi Bosch EDC16C34 Repair After Intermittent Starting and Lost Scan-Tool Contact

Intermittent starting was only half of what the garage reported on this Ford Focus 1.6 TDCi. Their diagnostic equipment could not always connect to the engine ECU either, so the second fault came and went just as the first did. Inspection of its Bosch EDC16C34 engine ECU, 0281011701 with Ford number 4M51-12A650-YD, found dry solder joints along the connector.

Two faults that would not stay put

A fault that shows every time can be followed on the car. One that is sometimes absent is harder to pin down, because the car may start when it is being checked and a scan tool that failed to connect once may connect the next time.

Here the second complaint made the first harder still. When the scan tool could not connect, the garage could not question the ECU at all, so the tool a garage usually leans on for an engine fault was itself part of the problem.

The ECU came to us from the garage. We take units in by post from anywhere in the UK, which means a garage needs to send nothing but the unit itself.

A full test, then a look along the connector

Every unit is logged when it reaches us, inspected by eye and tested electrically, then put through diagnostics chosen for the fault described. After the full ECU test on this one, we told the garage it was faulty and could be repaired. They had that result before any repair was carried out, and the repair waited on their agreement.

Inspecting the ECU turned up two findings: dry solder joints along the ECU connector, and signs of water ingress. The record lists them side by side. It does not say one led to the other, and this page does not either.

The connector is the unit’s boundary with the car. Everything the car asks of the engine ECU passes through it, and so does every request from a scan tool. On this unit, the dry joints sat along that boundary.

That fits what the garage saw. Both complaints came and went, and the joints we re-soldered were at the connector. It is what this job showed, not a rule: another Focus that starts only some of the time may have its fault somewhere else, inside the ECU or outside it.

Re-soldered, cleaned, reworked and retested

We re-soldered the connector, then cleaned and reworked the board. Board-level work here is done with a microscope and with rework tools held at a controlled temperature.

The unit then went back on test, to confirm the repairs were successful, and they were. A repair is only signed off once the unit has passed that final testing.

The repair carries our 24-month warranty.

Which numbers to give on the Repair Form

Bosch 0281011701 is an EDC16C34, and it is on record from the Focus 1.6 TDCi and the C-Max 1.6 TDCi.

The Ford number on this job’s unit, 4M51-12A650-YD, is not the only one on record against 0281011701. 6M51-12A650-NA is too, and it is the one shown on the EDC16C34 page listing this Bosch number. When you fill in the Repair Form, give the Bosch number first and copy the Ford number exactly as your label prints it; the Bosch number is the steady reference.

If the label on your Ford reads differently, the Ford-badged units we repair may cover it. If the car is not a Ford, start with engine ECU repair, whatever the badge.

If a Focus or C-Max with a 0281011701 unit starts intermittently, or a scan tool will not always connect to it, use the Repair Form to describe when the fault shows and when it does not. Testing starts once the unit reaches our workshop.