Random momentary 'Check engine' + 'traction control failure'

Some weeks ago, The Duchess started to ”miss” when cold: I put it down to the damp weather affecting the electrics. Yesterday, however, she randomly stuttered for a while longer than previously but, again, about 10 miles into the journey, seemed to behave.

Today, I thought I’d see if there were any DTCs. After running normally for a few minutes, revs randomly dipped to almost zero, the ”CHECK ENGINE” error appeared, then very briefly ”TRACTION CONTROL FAILURE’. Revs then returned to normal.

My ELM327+Torque app told me that there were ”No codes in ECU 0”, which didn’t seem right. I plugged in my other reader, a U480. That displayed only 1 pending code, P1797 which is a CAN error.

The battery is a brand-new Yuasa HSB019 - https://www.halfords.com/motoring/batteries/car-batteries/yuasa--hsb019-silver-12v-car-battery-5-year-guarantee-161078.html - less than a fortnight old with tight connections so I don’t think it’s the culprit.

As I also (still) have rev-related interference on the radio, I strongly suspect either a plug or plug lead breaking down.

What do we think?


I had a similar Rev related noise on my radio, turned out to be the Alternator Suppression Module which is located under the drivers side front fender (wing) on Canadian models, UK passenger side. Easy to change…

Its basically a big capacitor to suppress ignition noise. I got one from Ebay
Looks like this image

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Thanks for that, Ian. I’ll add that to the ever-growing list of ”to-do” jobs!

Meanwhile, I did some reading and it seems that the error messages were probably caused by the diagnostic software running. Indeed, one of them that I tried, Calista, actually displays a message to that effect.

I’m not sure all cars got a Suppression Module

I also think in the XJ it was located by the starter or by the battery