New exhaust, new CEL (1 Viewer)

[RyanTomorrow]

Hi y’all,

So I finally got around to installing a full exhaust replacement for my 1997. On the recommendation from @beno I went with a Magnaflow y-pipe and cats, with a Borla cat-back and brand new Denso O2 sensors.

Since install, I’ve been getting a CEL with a code P0125, insufficient coolant temp for closed loop fuel control. So my question is what might be causing this? Is it a:

A) faulty O2 sensor?
B) incorrectly installed O2 sensors?(swapped upstream/downstream)
C) something else?

Also the Borla muffler rattles pretty loudly at light throttle - anyone else have one with a similar issue?

Thanks for any help. Frustrating!

 

[dallen341]

Perhaps coolant temp sensor is going bad and it is coincidental.

 

[RyanTomorrow]

Hadn’t considered that! Occam’s Razor and all.

 

[Cruzilla]

Is your rattle in the muffler or is it exhaust pipe against the frame or heat shield above the rear axle?

 

[RyanTomorrow]

Good question - hard to diagnose solo, will have to crawl under while my kid brings the RPMs up

 

[Tools R Us]

That code is most often a wiring/connection problem, open. If it were a coolant sensor problem should get P0115/P0116 code(s).

 

[RyanTomorrow]

Just to close the loop, turns out one of the leads to the upstream O2 on the harness side had broken at the connector (hadn’t noticed because it was broken right at the end). Quick splice from @beno using a heat shrink butt connector, cleared the code. All good (still have a rattle, though).

 

[Cruisin4Miles]

Rattle has to be coming from something hitting the frame. New muffler itself shouldn’t be causing that noise. if It were a faulty muffler, it should sound bad throughout the RPMs. If the exhaust was welded onto the frame instead of using the Rubber hangers, this could cause the rattling too.