Do not have a Diesel, but a 4.8l E70.

I was kind of fighting an intermittent P0597 (thermostat heater control circuit open) that seemed to be somewhat temperature dependent.

After some investigation I finally determined the female terminals in the connector seemed spread and loose. So I just took a pick and gently and slightly closed the female terminal ends and when I plugged the connector back into the thermostat I could immediately tell that the connector was far more snug than before.

I have driving about 1500 miles and have been in temps as low as 30F and as high as 65F so far and the problem has not returned.

So I would attempt to check the female terminals in the MAF connector, the other problem I have been seeing on some models is the MAF wiring breaking right at the terminal crimp end inside the connector or back at the wiring box where the pigtail connects.

But I would try pinching the female connectors first. Quick, easy and cheap test.

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2008 4.8i Black with Tabacco. Black Y-spoke wheels and shadowline trim.