Question about 2003 Cadillac Seville STS

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Fix for 0170 & 0174 System to lean codes

2003 Cadillac STS codes 0170 and 0174, I have already replaced the plenum and plenum gasket as well as the intake gaskets, after 150 miles the codes came back and the car is running rough and first start of the day is hard, I don't know what to look at next

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  • Cadillac Master
  • 21,873 Answers

Well code 170 is for bank one and 174 is for bank two which you probably already know. The computer can not make the mixture rich enough to make the O2 sensors switch to rich.
Have you checked base fuel pressure and watched the data stream coming from the O2 sensors ? Very seldom do two sensors fail at the same time, but it could be something else like the mass air flow meter.

Posted on May 09, 2013


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GM Elec
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SOURCE: 2003 Cadillac CTS V6 Intake Manifold Gasket

Randy...There is no recall or service bullitens I can fing for intake gaskets. What is the reason for replacing the gasket.
Let me know.

Posted on Feb 11, 2009

  • 142 Answers


Yes, unfortunately it sounds like you have a blown head gasket. You can check your oil dipstick to see if there is any water in the oil and also check your coolant to see if there is any oil in the coolant. If so then you have a blown head gasket. The problem can only be resolved by having the heads machined and replacing the gaskets.
Please rate me and let me know if this helped.

Posted on Feb 11, 2009

  • 5660 Answers

SOURCE: my 1999 cadillac sts overheats alot i was told i

It hasn't been stated whether this is a Cadillac Seville STS, or an SLS. No matter, as they both use the 4.6 Liter, Dual Overhead Camshaft engine.

I would rate this as an 8, on a 1 to 10 scale. It would be a 10, if this Cadillac used wet sleeves. (Some Cadillac engines had a basic engine block, that had the water jackets open. The cylinders, are simply thick metal round tubes, with an O-ring at the bottom, and top. These set down in the block, and are held in place by the head.
There is a head gasket used also. When doing head work, or anything that involves removing the cylinder head, the wet sleeve cylinder, must NOT be disturbed from it's setting. If the cylinder is bumped, it can move, and the pattern the piston has made, will be disturbed. This means re-honing that cylinder. Lots of fun, these engines!)

Have you had experience with dual overhead camshaft engines? If yes, this is right up your alley. If not, be prepared for a small learning curve.

The engine must be removed. This is a transverse engine. The rear cylinder head May clear the firewall, it may not, if trying to remove it in the car. However, it is absolutely no fun trying to lay across the engine, and clean the gasket surfaces of the block!
This is just the tip of the iceberg, of bad things to come, when trying to replace the head in the car!

Just my advice.

Posted on May 18, 2009

  • 1 Answer

SOURCE: I need a cadillac seville sts 1998 4.3L & 32

Try Item #1 first it is the easiest.
Then Check the small water pump belt, it is not the serpentine belt.
The next step is to either check the Block with the following block tester available from NAPA
The part number is 700-1006
or change the thermostat dealer cost about 60.00 AUTOZONE about 40.00 You will need to purchase the Gasket with which ever you purchase from.

I had written a detailed note and the system dropped it. I hope this helps. coolant system drawing is available from:

Posted on Oct 05, 2009

  • 296 Answers

SOURCE: 1997 cadillac deville- misfires on cylinder #1

It sure is. If a plug is truly wet, the energy for the spark will travel through the moisture, rather than across the gap. The fuel air mixture flowing into and out of the cylinder serves to ventilate the cylinder, drying the plug.

Plus, that air is preheated, so that would accelerate the drying once warming up got underway.

You really need to have that head gasket replaced. If this questionable repair gives way (and it almost certainly will), you can get enough water in the cylinder to start breaking things on startup without any warning.

Posted on Jun 29, 2010

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System to lean means that a fuel injector or injectors may be plugged up, or the oxygen sensor is sensing too lean of a condition.

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Replacing the gaskets will usually fix this problem. Sometime the intake plenum will warp and need to be replaced as well. Replacing the O2 sensors will not fix this problem.

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