Hi Guys and Gals,

not your typical O2 sensor issue. I have been trying to track down either an issue with the O2 sensor setup OR possibly another fueling issue. Reason for diagnostics is failed emissions with brand new cats.

First of all my RAVE pdf states:

1996
Pin 33 - LH PRE Sensor
Pin 34 - RH PRE Sensor

1997 - 1999
Pin 33 - RH PRE Sensor
Pin 34 - LH PRE Sensor

I have a 1996 BUT my sensors are setup like 1997+. If I swap the sensors around I get a full RICH on one bank and a full LEAN on another bank. So it would appear that it wants to be as 97+

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Secondly I have an issue with the swing pattern on PIN 33 - currently RH PRE sensor. Pin 34 switches fast and very close to 0v and 5v. Pin 33 switches very slowly in comparison and is closer to 1v and 4v at its peaks. I have swapped left and right sensors and the results do no change banks.

I have a good 4.95v on both front plugs, a good 12v on both front plugs. Grounds show good with a maximum of .02v and good continuity to ground.

Either something strange is going on with the wiring somewhere on that bank OR for some strange reason that bank is being fueled differently.

Any suggestions???

 

Here's a page from the GEMS manual (whole one is a free download below) - item 9 perhaps indicates speed difference.

 

Since it did not switch sides when you switched the sensors, it suggests a possible ECU issue? Have you looked in it?

 

I don't know if it CAN be the ECU at this point. The ECU is sending the 5v reference and the sensor ground - it should be all down to the 02 sensor to do the switching/swing part of things.

The good bank with a DVM will go somthing like 4.9v 4.8v 0.1v 0.1v 4.9v
The other bank is like 4v 3.8v 3.6v 3.4v 3.2v 3v 2.8v 2.6v ....... and so on

graphing these in OBD2 shows the first as a nice "SAW Blade" and the second more like sea waves.

 

ps when you say look in it - do you mean anything specifically?

I do have a good graph of what the O2 swing points should be but I have nothing to measure them precisely. All I can go by is the shapes/patterns and trends.

 

As I understand it, the O2 sensors provide an input to ECM do they not? And the ECM determines the fueling ratio or whatever the appropriate term is.

I have seen photos and reports of corrosion internal to the ECM and similar issues.

Apparently there is some voltage drop somewhere in the circuit or possibly degraded components which I think are limited to inside of the ECM if the sensors themselve are good. Unless there is a wire harness related issue.

My 97 was plagued with corrosion on electrical connection when I first bought it several years ago.

These are just my general observations from past experiences. By no means a
X-Spurt on such matters.

 

Normal O2 sensors as you say create a voltage of their own. Ones used by Land Rover at the time are different. They are sent a 5v reference and a ground. The resistance of the sensor changes and and the ECM looks at how much of that 5v is sent back (just like a TPS sensor for instance).

 

By far the most common used sensor is the Zirconia which is the one you talked about. Land Rover at the time decided to use Titania sensors. This is reason you cannot use the cheap "ebay" sensors on these vehicles even if they are both 4 wires.

Oxygen sensor - Wikipedia, the free encyclopedia

 

Also when I'm checking the voltages I'm checking the wires going to the ECU plug.

 

OK, I guess that pretty much eliminates the ECU and only leaves the wiring and sensors?