Recent Rebuild; CEL indicates bad O2 Sensor

FLYERSTOYOU

MEMBER
1999 DODGE INTREPID
2.7L
6 CYL
FWD
AUTOMATIC
149,000 MILES

Hi guys!

Well.I just had the "infamous" 2.7 rebuilt on my 1999 Dodge Intrepid. Ugh! However, while the car now runs perfectly fine, and has much more power than I remember it having in recent years, I now have a CEL with codes P0154 and P0155. I know those codes point to O2 sensor issues, but the CEL has never been on since I bought the car 9 years ago. Never! Until the rebuild, that is.

So my question is.

Is it possible that something happened during the rebuild to cause this to happen? The timing of this suddenly happening would seem more than just mere coincidence. It appears the electrical connection is tight, and yes.I guess it's possible that the O2 sensor actually IS bad, but again it just started happening after the rebuild.

I read somewhere that before automatically replacing the sensor, I may want to check for vacuum leaks, intake manifold leak, fuel filter issues, etc. It's those kinds of suggestions that lead me to believe that it may not actually be a bad sensor, but rather something else having to do with the recent rebuild?

Any suggestions? Is it possible that as a result of the rebuild, everything is just "settling in", and that perhaps the code was thrown as a result? In other words, would things settle down after 500 miles or so. Reset the ECM. And perhaps not have the CEL happen again? New pistons, rings, etc. Needing to properly seat? Can blowby or something trigger the CEL? After a rebuild, the thought of spending more money on an O2 Sensor replacement seems like pouring salt in the wound (especially if it doesn't actually correct the problem). Any advice would be appreciated!

Thank you so much for your advice! I'm obviously NOT a mechanic, but I'm a pretty darn good graphic designer! LOL!

Dave

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,872 POSTS

P0155 - O2 Sensor 2/1 Heater Performance
Possible causes:
- Faulty Sensor (H2OS) Bank 2 Sensor 1
- Sensor (H2OS) Bank 2 Sensor 1 circuit fuse
- Bank 2 Sensor 1 harness is open shorted to ground
- Bank 2 Sensor 1 circuit poor electrical connection

PO 154 -- O2 Sensor 2/1 Circuit Open
Possible causes:
- Faulty Front Heated Oxygen Sensor Bank 2
- Sensor Bank 2 harness is open or shorted
- Sensor Bank 2 circuit poor electrical connection
- Fuel pressure incorrect
- Faulty fuel injectors
- Intake air leaks
- Exhaust gas leaks

These are the common causes of these codes. Since the engine was out and rebuilt, my first guess is there is a pinched wire or broken wire to the sensors. Check that first.

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Monday, July 14th, 2014 AT 7:39 PM

FLYERSTOYOU

MEMBER
1 POST

Jacob and Nicklaus,

Thank you for the feedback. Yeah, I read the same thing. But I'm not sure how to check for things like open grounds, ground loops, etc. I think I'll wait til my 500 mile checkup at the rebuild place, and have them try to find it. Although I suspect they're going to want to simply replace the O2 sensor and "see what happens".

Thanks again for your reply.I really appreciate it!

Dave

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Tuesday, July 15th, 2014 AT 7:27 AM

JACOBANDNICKOLAS

MECHANIC
109,872 POSTS

Dave,

If you decide that you want to try and check for issues, let me know. I can try to walk you through the process. It is a little of a pain and requires some basic tools, including a multi-meter, but you should be able to do it.

Since the problem started since the engine was rebuilt, make sure they are aware of it so they don't think it is a new problem and charge you for it.

Take care,
Joe

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Tuesday, July 15th, 2014 AT 9:44 PM