Mil command status failed 99 grand prix - 2004 Pontiac Grand Prix

That means the check engine light is on.

This code does indicate a bad thermostat. Are there any other codes?

1000000 hits world wide
the gas cap is loose.
use a scan tool to reset it ,
pull battery if losing all other BRAIN, programming is lost.
some radios have a code, get the code first. and write it down.

loose or bad cap, do drive and clear this DTC is a long battle.
"called driving cycles"

So you are saying the bulb for the check engine light is burned out and needs to be replaced ??
And the trouble codes you listed are for lean fuel mixture which could point to a vac leak or low fuel pressure.

if a car misfires its going to create heat , check your us army e-mail

solenoid switch valve latched in lr position

DTC P0641 The powertrain control module (PCM) provides a 5-volt reference to the following sensors:

The throttle position (TP) sensor 1
The accelerator pedal position (APP) sensor 2
The engine cooling fan speed sensor
The AC pressure sensor
The fuel tank pressure (FTP) sensor
The oil pressure sensor (OPS)
The PCM monitors voltage on the 5-volt reference circuit. If the voltage is higher or lower than required, DTC P0641 will set.

Conditions for Setting the DTC
The PCM detects a voltage that is higher or lower than required on the 5-volt reference circuit. The above condition is present for 1 second. Action Taken When the DTC Sets The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. A current DTC, Last Test Failed, clears when the diagnostic runs and passes. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. Clear the MIL and the DTC with a scan tool.

Yes i can be dangerous, depending which issues mentioned above has triggered the code such as a faulty gas peddle position sensor. the code can also cause a reduced engine power to activate.

Thank you for using Fixya and best advice is to have the dealer address these issues. A tech 2 scanner would be needed to address the P0641 DTC code.

Unfortunately it's a (relatively) one year only engine (without major component changes). However, these will fit without those changes:

'97, '98, '99 Buick Century,

'98, '99 Lumina (car),

'98, '99 Grand Prix,

'99, Monte Carlo.

This is assuming that you have an (8th digit) "M" VIN. Off the top of my head.

There are SO many things that could be to blame, such as a relay sticking in the Engine Management System, which controls fuel cut-off on deceleration, for example.

Have you changed the fuel filter yet?
If it's the original on a 99 model and a previous owner has run the tank dry, it will have sucked dirt into the filter.

Otherwise, the fuel pump may not be working efficiently.
Does the engine sound ok and maintain steady revs, around 850/900rpm when it's started up?

Couple things.
Temp. sensor may be shot, which usually tells fans to kick on at appropriate temp. Fan may be physically shot from usage. With car OFF, see if you can spin blade FREELY. It shouldn't turn hard at all, if so, fan bearings shot. Hard to say if MIL is related to this.