Advice needed please

[Johnsdutton]

Just got a 2001 2.0dti deisel estate.
Changed air flow sensor, removed and cleaned egr valve then refitted, changed air filter, changed oil.
When i switch ignition on all lights go out, car drives fine, but when stopped at traffic lights the engine management light comes on. Put car in gear drive away reach approx 25mph light goes out and car drives fine.
I can't figure out what is causing this, does anyone have any ideas?

[Gsi3.2]

for an intermittant fault like this, it really needs hooking up to a code reader to see whats amiss....you'd never guess with 100% accuraccy

[Johnsdutton]

for an intermittant fault like this, it really needs hooking up to a code reader to see whats amiss....you'd never guess with 100% accuraccy

Kinda thought that more in hope than anything else really. Thanks for prompt reply.