Ford Siemens SIM 21 Engine ECU Repairs

Type: Siemens Engine Management
Fits: Ford
Engines:
Year:
Fuel: Petrol
Ref: ECUT21175

Note: This ECU may also fit other models.

Three of the four engine ECUs in our Ford Siemens SIM21 table share one Siemens number, S118763003, and only the letter printed after it tells them apart. That letter has no fixed relationship with the Ford number on the same label, so neither can be worked out from the other. The sections below show which pairings are on record, why the fourth unit behaves differently, and what to send us.

One Siemens base number, three Ford numbers

Our table lists 2S6A-12A650-ZB, 2S6A-12A650-ZC and 2S6A-12A650-ZD, and on the labels our independent sources describe, all three are printed beside S118763003. What follows that base number is where they part company: ZB is on record with S118763003 C in seven sources, ZC with S118763003 F in ten and ZD with S118763003 G in six.

So a Siemens number read without its last letter narrows the table from four rows to three and stops there. Before you rely on it, make sure the letter has been copied as well; a label that has faded at that end still leaves the Ford number to settle the match.

Why the letters cannot be worked out from the Ford number

It would be convenient if ZB went with a B, ZC with a C and so on. It does not. The Siemens letters on record run C, F and G against Ford suffixes ending B, C and D, so there is no pattern to lean on in either direction.

In practice that means copying both numbers exactly as they appear, rather than completing one from the other. If the two on your label do not match any pairing above, send them anyway and say so; we will check the unit against what is printed on it.

2U7A-12A650-UD, the row that stands apart

The fourth Ford number starts 2U7A rather than 2S6A, and it carries a different Siemens base, S118763004. On labels described in our sources, that number appears with a D in seven cases and with an E in eight, so either letter is to be expected beside 2U7A-12A650-UD.

Our table prints S118763004 on this row without a letter. Here the Ford number is the one to match on, and a D or an E after the Siemens number is no reason to doubt it. Labels on this unit have also been recorded with 6STC after the Ford number, in eight sources.

The Fiesta 1.3 behind these numbers

Each of the four Ford numbers is on record from a Ford Fiesta: ZB in ten independent sources, ZC in thirteen, ZD in nine and UD in nine. As a family, the SIM21 numbers in our table are on record from the petrol Ford Fiesta 1.3, and ZB and ZD are each on record from that engine size individually.

The model is therefore a good reason to be on this page, but it will not choose between the rows. Within the table, the label does that work.

How a SIM21 is handled once it reaches us

Every SIM21 we work on arrives by post from a garage or owner somewhere in the UK, because this is a mail-in service. It is repaired in-house by our own engineers, on our own equipment.

The unit is logged, inspected and tested electrically, then diagnosed against the fault you reported. Any repair to the board is made at component level, under a microscope with temperature-controlled rework tools, and the unit does not leave until it has passed a final test.

We tell you what testing found and quote for the repair before any chargeable work starts, and nothing proceeds until you agree. The repair we carry out is covered by a 24-month warranty.

What to write down before you send it

Some labels carry an extra short code after the Ford number, and our table prints one on each row. Copy it along with everything else legible on the label.

When you raise the job through our Repair Form, give the Ford number with any extra code printed after it, and the Siemens number with its final letter. Add the car the unit came out of and what it was doing when the fault appeared.

If your Ford number begins 1S6A, see whether it is one of the 1S6A-12A650 numbers we list under SIM20. A Ford unit that is not in this table may still be on our Ford hub, and an engine ECU from a car Ford did not build start from our main repair page.

Below, each Ford number is printed without hyphens and followed by its extra code, which makes it the column to match on first.

Common part numbers associated with this type of unit