Down Stream 02 Sensors

[DesertDawg]

Hi All,

Greetings from the UAE.

I would like to know if the two downstream o2 sensors affect fuelling.

I have no Cat and my rear two O2 sensors are absent (XJ 2001 4.7L).

Forums have two conflicting views:

The ECU:

1/ Takes into account rear 02 sensors for fuelling/ignition.

2/ Only uses it for cat efficiency.

I ask because the CEL is annoying me and I want to build a couple of 02 simulators to turn it off (have 138, 158 codes) - but I want to know if this would affect fuelling first.

Dave

[SilverXJ]

I haven't seen anything that indicates the rear sensors are there for anything but cat checking in anything with a 4.0L. Install the sims.

[DesertDawg]

Thanks Chris.

Dave

[Cheromaniac]

The signal from the upstream sensors is used by the ECU to adjust the A/F ratio for closed loop operation, while the downstream sensors monitor the function of the cats.

[DesertDawg]

Thanks Dino