engine management light

when driving at high revs for any period of time my eng man light comes on?

once revs have dropped for a while it tends to go off.

plug in my OBD2 code reader and no codes are there?

any one any ideas?

What engine?

zoolander said:

what engine?

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td4

Generic code readers pre 2004 will not work, It could be a few things so would be better to get it hooked up at an independent and take it from there, if I had to have a guess would look at a over boost problem, which again could be a few things from a faulty sensor, sticking vanes on the turbo to a semi blocked cat.

Low fuel pressure from fuel pump under rear wheel arch will bring on mil light

With what I know now, the first thing I would do is change the harness to the rail pressure sensor, at about £30 to buy and an easy half an hour to fit, it is the cheapest item to try first. If it is not the problem then you are not to much out of pocket, it did cure multiple warning light problems on mine, the next item I would check is the fuel pump.