355 Check engine and Slow lights cycling

Hi Everbody

Got a wierd problem

The 1-4 engine bank Check engine light comes on for 1 second , and then turns off. Then the Slow Down light flashes for about a quarter second.
This happens every 5 secs under 3000rpm, every 10secs under 4000rpm, and about every 15secs over 4000rpm.

Each time it cycles the air pump relay clicks once.

There are no fault codes in the ECU, and the car drives OK.

Have swapped over the 2 Motronic 2.7 ECUs, and the CAT control units, but it still keeps doing the same thing on engine bank 1-4.
Any ideas folks??

Best regards

Chris

 

Hi Thanks for your replies.

It turned out to be a dead relay for the rhs ecu that resides in the passenger footwell.

But what a wierd result from just a dead relay solonoid coil

Thanks

Chris