I have a Peugeot 406. The engine service light comes up usually when the air-conditioning system is turn on and the car losses power ie, one or two plugs ignition current cut off. Sometimes it happens even without putting the air-conditioner on.

SOURCE: loss of power on hills

Hi, i think i answered you in another post.
If not then the likely cause of your problem is turbo related the most common cause is one of the pipes going to the turbo has a small split in it causing this problem.

Nearly all the diesel turbo cars with your problem usually means a pipe needs replacing for the turbo this will need to be checked as it can be difficult to find the damaged pipe because they work under high pressure so actually seeing the damaged part can be difficult so check properly.
If you are unsure then get a garage to check this as they will know the fault and will have a good idea exactly which pipe is damaged.
Worst case of this will be that the turbo needs replacing but this is in the most severe of cases the turbo can blow if the pipe has been damaged for to long as it will be working under the wrong pressure.
What happens is when you acelerate the turbo builds up pressure giving you more power when you need it but when the pipe becomes damaged this pressure is lossed and you then lose power and will cause black smoke coming out of exhaust.

Hope this is some help to you but if you have any problems or questions then give me a shout back and ill be glad to assist you further ok

SOURCE: service stability system

one of the four load stability sensors (one at each wheel suspention arm) has gone awry. Computer diagnostics (Advanced scan tool) will tell you which one. Suggest replace both on front or both on rear (whichever the case)

SOURCE: 2003 Expedition jerking/cutting out.

Had same problem: cutting out at low rpm, jerking, a huge clunk or shudder at higher speed (like transmission was going out), and rough idle. All these symptoms were intermittent.

CHECK THE FUEL FILTER!! Changed the fuel filter and thing runs fine!!

PS mine 2003 expedition has 105k

SOURCE: 2002 Saturn Vue V6 Loss of Power

Yup. The throttle body connectors have a history of failing on these cars. Replace the throttle body and the wire connectors that go to it, and you're back in business. Not terribly difficult and you can get the parts from any dealer. Saturn actually has a bulletin out on this problem but they won't cover it unless you're under warranty - no recall for this.

SOURCE: peugeot 406 hdi electronic immobiliser warning

The ignition key may be defective or in need of a battery to generate the code needed to disarm the immobilizer. Hope this helps!