Peugeot Partner Running Rough With Boost, Throttle and Intake-Leak Codes, Traced to Its Siemens 5WS40025E-T ECU

The fault codes on this diesel Peugeot Partner each read like trouble somewhere else on the van. Our bench test on its Siemens 5WS40025E-T engine ECU found the unit itself faulty, and we repaired it.

The van was a 2.0 HDi; the unit, a Siemens SID801. More on the type as a whole sits on our Siemens SID801 page, which includes Peugeot.

Rough running, and codes the van kept logging

The van was running rough and kept logging fault codes for turbo boost pressure, throttle position sensor and air-intake leak detection. Boost pressure belongs to the turbocharger’s side of the engine, while throttle position and intake-leak detection concern the air it draws in. Taken at face value, each of those codes reads as a fault somewhere on the van rather than in the ECU.

Before sending the unit, the customer had the turbo checked and fitted new parts. The rough running and the codes carried on regardless. With their other options exhausted, they posted the ECU across for testing.

What the codes could not tell anyone

Each code is a report the ECU makes when a reading falls outside the range it expects. A code alone cannot show whether the fault lies with the van or inside the unit making the report. The ECU reads those inputs and acts on them, so it stayed a possible source even after the work on the van. Bench testing the unit away from the vehicle is how that second possibility gets checked.

Units come in by post only, from senders UK-wide. Every one is booked in and looked over, then electrically tested before diagnosis narrows to the fault. This 5WS40025E-T did not pass our testing, and we confirmed the unit faulty. Two more numbers were recorded on it: SW 9646801080 and HW 9644323980.

Agreed, repaired, then tested a second time

We set out the faults for the customer, and they gave us the go-ahead. Nothing billable is started until whoever sent the unit has agreed.

The repair itself was component-level work, done with a microscope and temperature-regulated rework kit. Nothing went out to another firm; the engineers who repaired it work for us, here in the workshop.

After the repair we tested the ECU again, confirming that each fault had been put right. A repair counts as finished here only once it clears that final test. The customer got the ECU back working fully, and the repair we made sits under 24-month cover from us, which cannot pass to anyone else. Being the van’s own unit, it needed no recoding when refitted and went straight back in, plug & play.

Reading a 5WS40025E-T label ahead of posting

Where a label shows 5WS40025E-T, sellers’ listings add a little more about that number. Those listings name the Peugeot Partner against it. They give its type as Siemens SID801. They pair it with HDi engines. A label printed with a different Siemens number is not covered by any of this.

No part number can tell you if one particular ECU works; testing alone can. An illegible label need not stop you, because our engineers can find out if we repair that unit.

Prices are on application. To ask for one, complete the Repair Form, setting out what the van is doing. Further Peugeot engine units are gathered on the Peugeot hub, and What We Repair offers a sample across other makes.