: Codes P0171, P0174 and P1258 come up on 1997 Deville



brojake316
07-07-13, 11:54 PM
I have a few codes that are up on my 97 Cadillac Deville. P0171,P0174 and P1258. Could someone tell me what id have to do to fix em? I've read that the P1358 means that the engine has went into like a protective mode due to the coolant getting hot in the engine if so does that mean that its preventing the heads from blowing?

maeng9981
07-08-13, 05:54 AM
P0171 and P0174 together pinpoints to a vacuum leak between the MAF sensor and the intake valves. Usually when there are two codes together, the parts that are shared by both banks are usually at fault. This isn't important however, when you have P1258 - Engine Coolant Overtemperature.

Your engine went into the "camel mode" in one or more occasions. Now this could have been caused by several things; you need to put some more info about its current condition. Does it overheat? If so, when? Can you describe the overheating situation, how fast you were going, accelerating or coasting or idling, hilly road or flat road, things like that?

Submariner409
07-08-13, 06:31 AM
1997 = OBD-II diagnostics.

Use this in the future. Open the link and save the address to your bookmarks - you'll use the definitions as long as you own the car.

http://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

brojake316
07-08-13, 08:01 AM
P0171 and P0174 together pinpoints to a vacuum leak between the MAF sensor and the intake valves. Usually when there are two codes together, the parts that are shared by both banks are usually at fault. This isn't important however, when you have P1258 - Engine Coolant Overtemperature.

Your engine went into the "camel mode" in one or more occasions. Now this could have been caused by several things; you need to put some more info about its current condition. Does it overheat? If so, when? Can you describe the overheating situation, how fast you were going, accelerating or coasting or idling, hilly road or flat road, things like that?

OK so which isn't important the vacuum leak or the P1258? Yes the car over heats when I run it with the ac on over a period of say 30-45 minutes. Other then that it doesn't over heat.

Submariner409
07-08-13, 08:32 AM
If the car overheats with the A/C system ON, are the cooling fans running in SLOW ?? They should - any time an A/C function is selected. With no A/C function selected fans are controlled by the ECT sensor feeding the PCM and will go to SLOW at 224 degrees, the engine cools to 213, fans stop and the cycle repeats.

Pop the hood - start the engine, A/C ON. Fans should be running. If not, it's fuse/relay/wiring checks time.

maeng9981
07-08-13, 01:36 PM
If your car is overheating then deal with lean conditions (P0171/P0174) later.

If your fans are running with A/C and it still overheats, it's time for a block test.