P0151 and P0174 code help!

[Margaret]

Hello, I have a 2000 Seville SLS 4.6 that has been sitting for about 10 months in my driveway (my husband's car - he stopped driving it because it was overheating and didn't want to deal with it). Anyhoo, I know pretty much nothing about cars, so I enlisted the help of my Dad, the manual, and the internet to get this thing moving! The overheating was a hose that was spilling coolant all over the place and we fixed that no problem.

We pulled the following codes off the car : P0174 and P0300. The car was idling pretty shakily, but it would start after we recharged the battery. We changed the air filter, added more oil, and checked as best we could for vacuum leaks. We changed the spark plugs and those rubber things that go around the spark plugs and found both of those codes to remain. We checked the spark plugs again and saw that one wasn't firing which led us to replace the front coil pack (there was a hairline crack on the 2nd coil-thing). That got rid of the P0300 code and the check engine light. Today, we were driving it around and the light came back. We have P0174 (System too lean Bank 2) and P0151 (HO2 sensor circuit low voltage Bank 2, Sensor 1) now.

Sorry about the preamble, but here are my questions:

Does this sound like a bad O2 sensor could be causing both of these errors?

The car has about a half a tank of gas (and a bottle of Lucas we just put in there), should I add new gas to the mix to dilute the stale gas?

How long should I drive the car before I get emissions tested (after we finish the repairs)?

Would anyone like to buy a Seville? (just kidding!.... sort of...)

Sorry that I don't know all the names for the parts, but any advice you give I can have interpreted by my dad!! I would appreciate any insight! Thanks!

[Cadillac Jim]

Usually one bank lean but not the other means that there is a vacuum leak. There are some pretty sneaky vacuum leaks:

• Oil dip stick not all the way down, or the cap on the dipstick that caps the tube bent or missing.
• Oil filler cap loose or missing.
• PCV valive stuck, or not inserted or tight in the cam cover. Or, the hose on the PCV valve split or cracked.
• Any of the other vacuum lines on the throttle body can leak air. The EVAP lines go a long way, clear to the back of the car.
• The throttle body can have a bad gasket or be loose, too.
• The manifold might have been off and not put back properly.

Low voltage on an oxygen sensor usually means that a connector is loose or off, or that a wire has the insulation rubbed or burned off and is shorting out

So long as the check engine light is on, the car won't pass emissions testing. Most Powertrain codes will also prevent the car from passing inspection, even if the Check Engine light isn't on. You can reset the codes but there will be a "Not Ready" code if you get it inspected before you drive the car enough to give the code a chance to come back if there is still something wrong.

If you are serious about selling the car you can put a post in the For Sale board on Caddyinfo. You will sell the car a lot quicker and get a lot more for it if you complete the process of clearing out the cobwebs and getting it running smoothly with no codes.

[JimD]

....Today, we were driving it around and the light came back. We have P0174 (System too lean Bank 2) and P0151 (HO2 sensor circuit low voltage Bank 2, Sensor 1) now.

Sorry about the preamble, but here are my questions:

Does this sound like a bad O2 sensor could be causing both of these errors?

Could be an O2 sensor, or sensor wire harness damage. Could also be something else.

The car has about a half a tank of gas (and a bottle of Lucas we just put in there), should I add new gas to the mix to dilute the stale gas?

Absolutely. Stale fuel is very bad news for fuel injectors (and carburetors).

If it was my car, I would spend several hours cruising the Interstate at 70+ MPH with the gear selector in "3".

This would do two things; one is to get the engine RPM up to consume that stale fuel as quickly as possible. Two is to expose all the oxygen sensors (and particularily the bank 2, sensor 1) to long term constant operating temperature.

Clear all the codes and test drive the car.

Tell us what codes (if any) you have.

[Ranger]

Check for a crack in the plenum duct. That's the rubber coupler between the TB and the manifold. A common failure on the 2000+ engines. Spray some Brakleen under it (it usually rips on the underside where it can't be seen), and listen for an RPM increase. If none is heard, flex the duct with your thumb or put a screwdriver under it and lift a little to flex it and spray again.

[JimD]

Check for a crack in the plenum duct.

I would agree, Larry IF codes P0171 and P0174 were both reported. But that is not the case.

Based on what we have been told, the P0151 and P0174 codes are pointing at a "lean" condition on bank 2 only. A potential faulty bank 2 oxygen sensor OR a faulty / dirty bank 2 fuel injector could / would result in a lean condition on that bank only.

[Ranger]

Good point Jim.