Volvo Siemens Renix Engine ECU Repairs

Type: Siemens Engine Management
Fits: Volvo
Fuel: Petrol
Ref: ECUT176195

Note: This ECU may also fit other models.

Four names cover one engine ECU on the Volvo 440, 460 and 480. The cast alloy lid is stamped BENDIX or SIEMENS, the engine-management system inside is Fenix, and repair and parts listings file the same unit under Renix. Nobody involved is wrong, and nothing has been swapped.

Renix is a company name, not a component name. Renix Electronique was a joint venture between Renault and Bendix, and the French Bendix operation was later sold to Siemens, which is why two makers’ names appear on one design. Fenix is what the engine-management system they built was called; on these cars the generation is Fenix 3B.

One thing is worth establishing before a unit goes anywhere: whether the box in front of you is the 35-pin one. The engine ECU on the 440, 460 and 480 sits in a cast alloy case, has 35 pins and carries the maker’s name on the lid. It is an engine-management ECU, which means it controls fuelling — and that is exactly what the other Volvo part called Renix does not do.

That other part is the ignition unit fitted to the 340 and 360: an ECU with the coil attached, working from a flywheel sensor and holding a mapped ignition curve. It has nothing to do with fuelling and it is not the ECU described here. A 300-series owner searching for a Volvo Renix ECU will land on pages like this one, and the unit in their hands is a different component doing a different job.

What goes wrong inside these units keeps to a small set of patterns. Idle control that will not settle is one. Starting trouble that comes and goes — fine one morning, nothing the next — is another. The third is a loss of control over an output, where the unit stops driving something it is meant to drive.

The first of those has a cause that has nothing to do with age or wear. On some of these cars the idle control valve and the throttle position switch sit on identical, un-keyed three-way connectors, and both can come apart during work in the engine bay, while base idle or mixture is being set. Cross them over and the ECU’s idle-control circuit takes a direct earth the moment the ignition is switched on. The harm is done on that first turn of the key rather than building up over weeks. It is most likely on the 1.7, and if those two connectors have been apart, marking them before they go back takes a minute.

Not every symptom that points at the ECU belongs to it. On Volvo injection models up to 1994, an intermittent poor start or non-start is worth tracing to the radio suppression relay first. It is a white relay near the front wing and it feeds the injectors; when it starts to fail, the injectors mis-operate in a way that reads exactly like an ECU on its way out. Ruling it out before a unit comes off the car is far less work.

A unit that arrives here is logged, inspected and electrically tested before anyone offers a view on it. You are told what the testing found and what a repair would involve, and nothing chargeable begins until you have authorised it. The repair is carried out at component level on your own board, so the ECU that goes back into the car is the one that came out of it, and the job is not finished until the unit has passed final testing. The repair is covered by our 24-month warranty and the work is done in our own UK workshop by our own engineers.

Volvo applications outside this one are listed on the Volvo engine ECU pages. Units reach us by post from anywhere in the UK.

If the relay and the wiring have been looked at and a 440, 460 or 480 still has an electronic fault, the unit can be sent in for testing, with the repair quoted on application once we know what it needs. The Repair Form is how a unit is sent in.

Common part numbers associated with this type of unit