Fiat Punto Magneti Marelli IAW 59F.M3 Engine ECU: Loss of Power Traced to Failed Ignition Coil Circuits (P0351, P0352)

Loss of power and poor running could have sent the search almost anywhere on this 2001 Fiat Punto. The fault codes stored on the car were far narrower. Diagnostics showed two:

• P0351 – ignition coil 1 control circuit
• P0352 – ignition coil 2 control circuit

Each code names a circuit exactly. Neither says which part of that circuit has failed, and that was the question the Punto’s Magneti Marelli IAW 59F.M3 engine ECU came to us to answer.

What a coil control circuit code can and cannot tell you

The symptom and the codes do different jobs. Loss of power and poor running describe how the car felt to drive; P0351 and P0352 describe where the car’s own self-checks found a problem.

A coil control circuit is the path the engine ECU (ECM) uses to switch an ignition coil. A code against it reports a fault somewhere along that path: in the coil, in its wiring, or in the driver inside the ECU.

Two codes, one for each coil, do not close that question. The same pair could come from faults on the car or from the unit itself, so condemning the ECU on the codes alone would have been a guess. It was tested before anything was replaced.

A Fiat specialist’s diagnosis, handed to our bench

The ECU was sent in by a Fiat specialist in Scotland, whose customer had reported the loss of power and poor running. The garage had the car and the codes. What remained was the ECU itself, and that is the part a bench can answer.

Garages anywhere in the UK can post an engine ECU to our workshop this way while the car stays with them. Each unit is logged, inspected and tested on arrival, and no chargeable work starts until the sender has our findings and has given the go-ahead.

This one was booked straight into the workshop for testing.

Both ignition coil circuits had failed

Initial tests confirmed the faults the customer had reported. Both ignition coil circuits had failed: the circuit for coil 1 and the circuit for coil 2, the same two circuits P0351 and P0352 describe.

That placed the fault the codes had pointed at inside the engine ECU, on both circuits. The question the garage had passed on now had an answer.

Repairing the coil circuits and reworking the board

We repaired both coil circuits and reworked the board. We also replaced the components known to be common failure points on this unit, so the repair went further than the two circuits the codes had named.

The job record does not list those components or say what made the circuits fail, and this page does not guess at either.

Soldering on a board like the 59F.M3’s is done under a microscope with temperature-controlled rework equipment, and a unit does not leave us until it has passed final testing.

The repaired unit went back to the garage with a 24-month warranty. It was the Punto’s own engine ECU, so it kept its original coding and immobiliser pairing with the car.

Check the car’s side before refitting

A failed coil or a wiring fault on the car can produce the same codes, so rule either out, or put it right, before a repaired unit is refitted. The bench answers for the ECU; the car’s side of each circuit needs checking at the car.

The engine ECU from this Punto is Marelli’s 59F, covered on its own page, and other Fiat units are listed under the Fiat engine ECU hub this page hangs from.

If a car of yours is logging codes like these, use the Repair Form to hand over the codes along with the unit. Our main engine ECU repairs page is the place to start whichever car your engine ECU came out of.