IT's been a little bit since my last post but I'm back at it trying to track down the PO420 code that I can't seem to shake for like the last year. There are NO other codes or pending codes but the P0420. And my Fuel mileage has been normal 14mpg (city) and 18mpg (hwy). I use 93octane.

I'm Driving a 98D1 with 127k. Pertaining to the Emissions: I've replaced all O2's, Cats, Bosch +4's and Mag wires & the Coolant Temp Sensor.

I purchased a decent Actron CP9180 Scanner and can now view live data. Over the last few days I've been monitoring 02's; eng temp; fuel temp; MAF; Fuel System open/closed; So On and so On.

In A nut shell I'm thinking my ECU needs to be Flashed. Here's why:

Items that are Working correctly-
The o2's are all switching between .035v ~1.005v without any lags or sensors stalling.
Fuel Sys is Closing as it should after startup in the open postion.
Coolant Temp is right on sitting under 198deg under load or 185@ idle.
Short term Fuel Trim is hovering around the zero mark as it should.

The Only real issue that I see is the Long Term Fuel Trim is rock soild at -9.2
This number has not moved in days; under any driving contions or any amount of drive time. Nor does it clear when I clear codes or disconnect the battery. I'm thinking this is what is throwing the P0420 Code.

Any thoughts out there???

 

A420 code indicates your driver side cat is toast, replace it and you'll be set other then trying to find out what caused it to fail.

 

Mike, he mentions that he already replaced the cats

 

Yeah, that's the thing...I replaced them due to the orginal Po420 code. Even after the Cat replacement + other part replacements and multiple Code resets, I'm stil getting the same code.

I spoke to an LR only indie shop (of 15yrs) in Philly today and explained it to him. He was stump but very interstend in checking it out using his hand held T4. He said he would flash my ECM at no charge just because he likes a challange. I be tinkering around tonight, but I'll be taking it to the indie on Saturday morning.

On a side note. I did some poking around on the web last night for ECM & fuel Trim info for the rover Gems Engine and fould a great page for the 14cux Fuel injection unit that controls the Gems Motors. Some really good reading for us wrench heads.

http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

 

Maybe your cats are high...

 

Well that's an easy fix...One bag of doritos or "cat nip" Please

But seriously...salve7; are you serious?

 

In general? My name? or about the faded felines?

 

After doing some more tinkering around last night with the new scanner, there is a function for Diagnositic Tests. When I ran the test it produced 5 different sub tests that are specific to the 98 disco, each test is labled 1 thru 5.

Each test (1 thru 5) had the same test parameters:

- Test Data=
- Max Value=
- Test measure=
- Min Value=
- Test Status result=
- Module from were the test was produced=

4 out of 5 test came back "ok" in the -Test Status- result column.
Except test number (1). It read as follows:

- Test Data= 01
- Max Value= 3e8
- Test Measure= d5c
- Min Value= - - -
- Test Status Result= HI
- Module = $e8

Does anyone know what "5" different Diaganostic tests the 98 Disco computer can Produce?

or

What anything in the above list means?

The Actron manual states: "Refer to vehical Service Manual for test ID's and Definitions." The Rave states nothing for the test types or definitions the onboard computer can produce.

 

Wow, this must be driving you crazy, particularly as you have spent so much money already replacing the parts.
Too deep for me but I am following with interest, good luck.
Logically if you are getting a "toasted cat" code and the cat is new then whatever sensor sends the signal must be at fault. That's all I can think of. Can you trace the sensor wiring back and make sure there is no burning/continuity issues?

 

This is keeping my gear head spinning that's for sure....

My disco is my second Vehicle and as I tell my wife when I need to buy new parts, "I'm going to be buried with it". Since I'm in for the long haul with her (the Disco), it really doesn't bother me to invest for the parts. It's much better than all those "bad habbits" I used to dump money into!!!

I've traced the wires back and stuck a meter on them for continuity and all seems good. When I monitor the Volts via the Scanner, all of the o2's are switching nicely as they should. When I turn the engine off (key still in the on postion) all of the o2's instaniously read 1.020v all at the same time. They stay at this voltage until I turn the engine back on.